60 PART I Introduction to Geographic Information Systems ...fe257.forestry.oregonstate.edu/sites/fe257/files/Chapter4.pdf60 PART I Introduction to Geographic Information Systems, Spatial

60 PART I Introduction to Geographic Information Systems, Spatial Databases, and Map Design

Minnesota Planning, Land USDA Forest Service, Southern Washington Department of Natural Management Information Center. Region. 2001. Alabama: Resources. 2001b. Washington 2001. Minnesota geographic Geographic data files. http://www. Natural Heritage Program clearinghouse. http://www.lrnic. state.mn.us/chouse/ (accessed

southernregion.fs.fed.us/gis/ alabamat (accessed 1/10/03).

information order form. Olympia, WA: Washington Department of

11 10103). U.S. Geological Survey, Federal Natural Resources. http://www. Prisley, S. P., T. G. Gregoire, and J. L. Geographic Data Committee. 2002. wa.govldnr/htdocs/fr/nhp/refdesk/

Smith. 1989. The mean and Manual of federal geographic data gis/index.htm (accessed 1/10/03). variance of area estimates in an products. Reston, VA: U.S. Wolf, P. R., and C. D. Ghilani. 1997. arc-node geographic information system. Photogrammetric

Geological Survey. Washington De~artment of Natural

Adjustment computations: Statistics and least squares in surveying and

" Engineering and Remote Sensing Resources. 2001a. Digital GIs. New York: John Wiley and 55: 1601-12.

Schneider, B. 2001. On the uncertainty

- geographic data order form. Olympia, WA: Washington

of local shape of lines and surfaces. ~ L ~ a A m e n t of ~aturalkesources. Cartography and Geographic http:Nwww.wa.govldnr/base/pdf/ Information Sciences 28:237-47. neworder.PDF (accessed 1/10/03).

Sons.

62 PART I Introduction to Geographic Infornlation Systems, Spatial Databases, and Map Des~gn CHAPTER 4 Map Design 63

landscape features they attempt to present. Under- standing that maps must be created and inter- preted with a discerning eye is one of the first steps

I necessary to becoming a successful mapmaker or map user. 1' Maps usually are two-dimensional representations of landscape features (although three-dimensional maps can be used to show volume or perspective), that use symbols, colors, and text to represent spatial phenomena. Cartography is the art and science of making maps, and, although this book was not intended as a book on cartography, many of the applications at the end of this chapter emphasize the development and use of maps to help describe the landscape. Maps are graphic representations of information, as are graphs, flowcharts, and other diagrams. Maps attempt to get across ideas to users in a different manner than other types of graphic representations, with the hope that the human brain, with its limited capacity to store information, will have an added ability to understand those ideas (Phillips 1989). The design of a map can affect the ability to communicate spatial information; thus, a well-designed map will likely communicate ideas to coworkers and supervisors more effectively than a poorly designed map. Poorly designed maps can lead to misinterpretations by the intended users, facilitating costly or inappropriate decisions.

Maps should be clear enough to enable users to understand (1) the land area the map represents and (2) the message the map intends to communicate. In order to do so, a variety of common tools are used, such as north arrows, scale bars, legends, and neat lines. In addition, the landscape features illustrated on a map should include enough landmarks to allow map users to reference themselves to the mapped area and to help them navigate through a landscape. Two important aspects of maps that map developers should keep in mind are (1) not everything that is known about a landscape needs to be displayed on a single map and, (2) to communicate effectively, maps should focus on showing a limited number of landscape features. The landscape features primarily emphasized on a map should be those associated with the intent of the map. On a map developed to illustrate stream classes, for example, other landscape features, such as roads, timber stands, and soils, should be secondarily emphasized or omitted from the map entirely.

There are several basic components that are important to include in a map: the symbols being used to describe landscape feat~~res, a north arrow, the scale, the legend, locational insets, and the qualities (font, size, etc.) of the text (labels and annotation). In addition, tliere are

other components, such as a description of the map developer, the filenames and file locations of the GIs databases used, and map quality caveats, that some organizations may find necessary to include in a map. Each of these components is briefly discussed before venturing into the common types of maps that can be developed using GIS software programs.

Symbols A variety of map symbols have been developed to identify significant landscape features. Some symbols represent national standards for identifying landscape features, such as those found on U.S. Geological Sur- vey topographic maps (e.g., contour lines, hydrologic symbols) (figure 4.1). Other symbols represent organi- zational standards for identifying landscape features. For example, the U.S. National Park Service has created a standard set of symbols for use on National Park Service maps (National Park Service 2001). On a smaller scale, the University of Nebraska-Lincoln (2001) has developed standard symbols for use in its transportation maps, and the U.S. Orienteering Feder- ation (2001) has developed a set of standard map symbols for orienteering events.

Most GIs software programs also provide a set of standard map symbols for map users; however, map developers can easily misuse the symbols, since documentation is usually limited within the dialog

Buildings and Related Features

Buildina ~ O ~ E Z Z

School, church & A

Built-up area

Racetrack

Airport x 23% Landing strip - -----

L - - - - - '

-

Well (other than water), windmill 0 Y

Tanks @ Covered reservoir BE32

Gaging station B

Landmark object (featured as labeled) o

Campground, picnic area A n

- - I - - - -

Cemetery: small, large :_+::C_y !

Figure 4.1 Common USGS topographic symbols. (Source: USDI U.S. Geological Survey 2002.)

boxes provided by the software. Nevertheless, a vari- Graphic or bar scale: etv of svmbols are available in GIs software vrograms . - tod describe landscape features. It is also possible 500ft 0 500 ft 1000 ft

within many GIs software programs to create a cus- - - tomized symbol set. In some GIs software programs, symbols are merely bitmap graphic files, which can be Verbal scale: Representatwe fraction (RF):

edited or created through graphic software programs. 1 inch = 500 feet 1 :6000

Other programs the use of Figure 4.3 Graphical, verbal, and representative scales. tomized tools or products developed by third-party software developers, many of which are designed to

users and that scale (figure 4.3). When a representative fraction scale are specific to the GIs software program being used. is used, such as 1 :24,000, one should interpret the scale

as 1 unit on the map representing 24,000 units on the North Arrow 4"5\>,~& 'Jground (e.g.. 1 map inch represents 24,000 ground

Ordinal directions (north, south, east, west) are typi- 0 # inches, or 1 map centimeter represents 243000 ground cally used by map developers to indicate map direc- centimeters). Representative fraction and verbal scales tion. ~t is common for maps to use a north arrow to 5 are also interchangeable. For example, a verbal scale indicate the orientation of the landscape being par- *)that reads 1 inch = 1 mile is the same as a representa- trayed. Although most maps are usually oriented withr scale of 1:633360 (1 inch on a map represents north at the top of the page and south at the bottom, it 63,360 inches, Or 1 mile, on the ground) Graphic bar is appropriate to remove the uncertainty associated scales generally do not indicate the exact scale, as do with an interpretation of a map by explicitly indicating representative fraction or verbal scales, of a map but, the direction through the use of a north arrow. A vari- rather, associate the length of a graphical shape to ety of north arrows are available in most GIs software ground distances. Whether graphic, verbal, or repre- programs, and a number of others can be developed sentative fraction scales are used, the appropriate met- using lines, arrows, and text (figure 4.2). rics (English vs. metric system, feet vs. miles, meters

vs. kilometers) and appropriate font sizes should be employed to prevent map users from becoming dis-

Scale tracted from the map's main message. Scale bars have Scales indicate to map users the proportions of a map an advantage over representative fraction and verbal in relation to the landscape illustrated on the map- scales in that they generally adjust accordingly when that is, map distance compared with Earth distance. a map is rescaled or resized within a GIs software Scales can be displayed in a variety of ways, graphi- program. cally, verbally, or using a representative fraction (RF)

Legend N The information contained in a map legend should de-

scribe all of the landscape features illustrated on the map, allowing users to interpret the map fully (figure 4.4). Of course, if one intends to add mystery to a map, the legend may omit the description of certain landscape features. Rarely, however, does one want a map to be an enigma to users. Most GIs software programs now offer tools that allow the automatic creation of legends by referencing the GIs databases that are being used. Typically, tools are also available for GIs

Legend

- . - . . - . . . Streams Harvest area

Roads @ Log decksllandings

I Stand boundaries +-+ Gates - Property boundary Houses

Figure 4.2 Commonly used north arrow designs. Figure 4.4 Map legend.

62 PART I Introduchon to Geographic Infom~ation Systems, Spatial Databases, and Map Design I CHAPTER 4 Map Design 63

~ landscape features they attempt to present. Under- I standing that maps must be created and inter- I preted with a discerning eye is one of the first steps

necessary to becoming a successful mapmaker or map user.

I1 Maps usually are two-dimensional representations I of landscape features (although three-dimensional

maps can be used to show volume or perspective), that

i use symbols, colors, and text to represent spatial phenomena. Cartography is the art and science of making maps, and, although this book was not intended as a book on cartography, many of the applications at the end of this chapter emphasize the development and use of maps to help describe the landscape. Maps are graphic representations of information, as are graphs, flowcharts, and other diagrams. Maps attempt to get across ideas to users in a different manner than other types of graphic representations, with the hope that the human brain, with its limited capacity to store information, will have an added ability to understand those ideas (Phillips 1989). The design of a map can affect the ability to communicate spatial information; thus, a well-designed map will likely communicate ideas to coworkers and supervisors more effectively than a poorly designed map. Poorly designed maps can lead to misinterpretations by the intended users, facilitating costly or inappropriate decisions.

Maps should be clear enough to enable users to understand (1) the land area the map represents and (2) the message the map intends to communicate. In order to do so, a variety of common tools are used, such as north arrows, scale bars, legends, and neat lines. In addition, the landscape features illustrated on a map should include enough landmarks to allow map users to reference themselves to the mapped area and to help them navigate through a landscape. Two important aspects of maps that map developers should keep in mind are (1) not everything that is known about a landscape needs to be displayed on a single map and, (2) to communicate effectively, maps should focus on showing a limited number of landscape features. The landscape features primarily emphasized on a map should be those associated with the intent of the map. On a map developed to illustrate stream classes, for example, other landscape features, such as roads, timber stands, and soils, should be secondarily emphasized or omitted from the map entirely.

There are several basic components that are important to include in a map: the symbols being used to describe landscape features, a north arrow, the scale, the legend, locational insets, and the qualities (font, size, etc.) of the text (labels and annotation). In addition, there are

other components, such as a description of the map developer, the filenames and file locations of the GIS databases used, and map quality caveats, that some organizations may find necessary to include in a map. Each of these components is briefly discussed before venturing into the common types of maps that can be developed using GIS software programs.

Symbols A variety of map symbols have been developed to identify significant landscape features. Some symbols represent national standards for identifying landscape features, such as those found on U.S. Geological Sur- vey topographic maps (e.g., contour lines, hydrologic symbols) (figure 4.1). Other symbols represent organi- zational standards for identifying landscape features. For example, the U.S. National Park Service has created a standard set of symbols for use on National Park Service maps (National Park Service 2001). On a smaller scale, the University of Nebraska-Lincoln (2001) has developed standard symbols for use in its transportation maps, and the U.S. Orienteering Feder- ation (2001) has developed a set of standard map symbols for orienteering events.

Most GIS software programs also provide a set of standard map symbols for map users; however, map developers can easily misuse the symbols, since documentation is usually limited within the dialog

Buildings and Related Features

Building = U m E Z Z

School, church A A

Built-up area

Racetrack

Airport x s=&% Landing strip - - - - - -

L - - - - - . 2

Well (other than water), windmill (2 f

Tanks • @ Covered reservoir @@B

Gaging station B

Landmark object (featured as labeled) o

Campground, picnic area A n

- - I - - - -

Cemetery: small, large :_+::Gem : - - -,

Figure 4.1 Common USGS topographic symbols. (Source: USDI U.S. Geological Survey 2002.)

boxes provided by the software. Nevertheless, a vari- Graphic or bar scale: etv of svmbols are available in GIS software programs . - to' describe landscape features. It is also possible 500ft 0 500 ft 1000 ft within many-GIS software programs to create a cus-

A - tomized symbol set. In some GIS software programs, symbols are merely bitmap graphic files, which can be Verbal scale: Representai~ve fraction (RF):

edited or created through graphic software programs. 1 inch = 500 feet 1 : 6000

Other programs the use of Figure 4.3 Graphical, verbal, and representative scales. tomized tools or products developed by third-party software developers, many of which are designed to

users quickly that scale (figure 4.3). When a representative fraction scale are specific to the GIS software program being used. is used, such as 1:24,000, one should interpret the scale

as 1 unit on the map representing 24,000 units on the North Arrow $(& ("5\2~& .Jground (e.g., 1 map inch represents 24.000 ground Ordinal directions (north, south, east, west) are typi- 0 0 inches, or 1 map centimeter represents 24,000 ground cally used by map developers to indicate map direc- centimeters). Representative fraction and verbal scales tion. 1t is common for maps to use a north arrow to 5 are also interchangeable. For example, a verbal scale indicate the orientation of the landscape being par- *?that reads 1 inch = 1 mile is the Same as a represents- trayed. Although most maps are usually oriented withr F e scale of 1163,360 (1 inch on a map represents north at the top of the page and south at the bottom, it 63.360 inches, or 1 mile, on the ground) Graphic bar is appropriate to remove the uncertainty associated scales generally do not indicate the exact scale, as do with an interpretation of a map by explicitly indicating representative fraction Or verbal scales, of a map but,

the direction through the use of a north arrow. A vari- rather, associate the length of a graphical shape to ety of north arrows are available in most GIs software ground distances. whether graphic, verbal, or repre- programs, and a number of others can be developed sentative fraction scales are used, the appropriate met-

using lines, arrows, and text (figure 4.2). rics (English vs. metric system, feet vs. miles, meters vs. kilometers) and appropriate font sizes should be employed to prevent map users from becoming dis-

Scale tracted from the map's main message. Scale bars have Scales indicate to map users the proportions of a map an advantage over representative fraction and verbal in relation to the landscape illustrated on the map- scales in that they generally adjust accordingly when that is, map distance compared with Earth distance. a map is rescaled or resized within a GIs software Scales can be displayed in a variety of ways, graphi- program. cally, verbally, or using a representative fraction (RF)

Legend N The information contained in a map legend should de-

scribe all of the landscape features illustrated on the map, allowing users to interpret the map fully (figure 4.4). Of course, if one intends to add mystery to a map, the legend may omit the description of certain landscape features. Rarely, however, does one want a map to be an enigma to users. Most GIS software programs now offer tools that allow the automatic creation of legends by referencing the GIS databases that are being used. Typically, tools are also available for GIS

Legend

- . . -. . - . . . Streams Harvest area

Roads $ Log decks1Landings

I Stand boundaries t* Gates - Property boundary Houses

Figure 4.2 Commonly used north arrow designs. Figure 4.4 Map legend.

64 PART I Introduction to Geographic Information Systems, Spatial Databases, and Map Design I CHAPTER 4 Map Design 65

users to modify automatically created legends to suit their needs. Legends can take many forms and can use symbols, points, lines, polygons, colors, patterns, and text to clarify what viewers see on a map. Legends should also utilize the appropriate font and size of type without detracting from the message of a map. In addition, the appropriate descriptors should be used and ab- breviations avoided if interpretation might be unclear or if a broad audience is targeted.

organization and distinction to mapped landscape features. Some GIs software programs include mapping tools that will not only create a neatline but also allow one to specify how the area contained within the neatline will be filled. For example, the background area behind the map title, landscape features, and legend can be shaded. This feature allows one to produce a presentation-quality map or poster.

Map Annotation Locational Insets Map annotation, or text applied directly to the map, is It may be helpful for the audience of a map, depending important in further describing landscape features that on how familiar they are with the natural resource be- might be only briefly described in a legend. In some ing illustrated, to see a panel that shows the location . cases, it is not practical (or possible) to indicate all the of the mapped area in the context of a larger, more rec- landscape features of interest through the legend, due ognizable landscape feature, such as a drainage basin, to space limitations or the nature of the landscape fea- forest, county, or state boundary. Often, a map will in- tures. For example, ownership boundaries may be de- dicate these areas with a locational inset (figure 4.5). lineated with a certain type, size, and color of line, yet The locational inset might show the location of a the actual owners may be displayed on the maps with watershed within a drainage basin or the location of words, such as Georgia-Pacific or State of Alabama. a single stand within a forest. The locational inset Road numbers or names may be applied as labels to should be a minor component of a map and not com- maps to describe the road system further. The type of pete with the main features for audience attention. markings used to delineate treatment area boundaries,

Three other types of insets can also be used-an such as pink flagging or orange paint, may be dis- enlargement inset, a related area inset, and a special played at the appropriate places on the landscape de- subject inset. An enlargement inset can be used to scribed in a map. Surveying information, such as show more detail of a specific area located within the township and range numbers, may be illustrated on primary map region. A related area inset can be used maps with annotation (figure 4.6). Finally, owners of on a map to illustrate features that are noncontiguous homes near treatment areas may also be placed on with the main map figure yet are still important to dis- a map next to the symbol that defines their prop- play. Related area insets, for example, are often in- erty boundary, home, or other noteworthy landscape cluded in maps that illustrate the 50 United States; features. Alaska and Hawaii are positioned in the insets, rather than in their actual geographic location, which would necessitate illustrating portions of Canada and vast ex- V P O ~ ~ ~ P ~ Y panses of the Pacific Ocean. A special subject inset can The ability of GIs users to interpret the written infor- be used on a map to show different thematic represen- mation they find on maps is a function of many vari- tations of the main map area (e.g., precipitation, canopy ables that can be described under the broad heading of cover); it is a popular mapping approach used in many typography. Some of the most important typographical atlases. elements are typeface (font), weight (boldlnormal),

size (point size), and case (use of capitals) of text contained on the map itself. In one study, Phillips et al. (1977) noted that the capability of people to search for

Adding a neatline to a map is considered good carto- and find information on a map was enhanced when the graphic practice, but its presence is generally less crit- names of places were displayed in a normal weight ical than that of a scale bar or a legend. A neatline is a (not bold), with letters all in lowercase, except with an border that surrounds all of the landscape features on a initial capital. However, capitals should be used for all map but lies within the outside edge of the mapping letters in place names when names are difficult to pro- medium (paper) (see figure 4.5). Neatlines can also be nounce or need to be copied accurately. Names set placed around other map elements to help keep them entirely in lowercase have been found to be harder to separate from other objects (e.g., to separate the loca- locate than names set entirely in uppercase, with the tional inset from the legend). Usually, a neatline is initial letter slightly larger than the other letters in a composed of at least one line, but multiple lines can be name (Phillips 1979). The font chosen will undoubt- used to provide a more dramatic effect. Regardless of edly influence the ability of users to interpret the maps; the style, neatlines can be useful tools for bringing thus, a normal font (such as Times Roman, Arial, or

Neatline

Judith Basin I and major streams In

Legend Montana State

Judith Basin - Streams

Prepared by Michael Wing Date: November 17,2002

Locational inset

Figure 4.5 Locational inset and neatlines.

Univers) and a normal, consistent font size are appropriate for most maps.

Source Information and Footnotes In some large natural resource management organizations, where data development tasks are shared by multiple people, placing the names of the people who contributed to the development of a map on the map is discouraged. However, in field -offices of natural resource management organizations, where field person-

nel are generally responsible for developing maps to assist with on-the-ground decisions (and, hence, not specifically the development of GIs databases), it may be desirable to know who created a map and when it was created (figure 4.7). Since GIs databases may be modified frequently, knowing the date that a map was created might be as important as knowing the developer of the map. This source information allows map users to place the content of a map in perspective with the version of the GIs database(s) used to create the map. For example, suppose it is currently September

Neatline

\ Judith Basin / and major streams A%

CHAPTER 4 Map Design 65

nel are generally responsible for developing maps to assist with on-the-ground decisions (and, hence, not specifically the development of GIs databases), it may be desirable to know who created a map and when it was created (figure 4.7). Since GIs databases may be modified frequently, knowing the date that a map was created might be as important as knowing the developer of the map. This source information allows map users to place the content of a map in perspective with the version of the GIs database(s) used to create the map. For example, suppose it is currently September

Legend Mnnta

#? Judith Basin - Streams

I ...-...- lna State

50 Kilometers I \ 0 10 20 30 40 Judith Basin

Prepared by Michael Wing -A noto. hlnrromhor 17 ~ n n ~ a . Figure 4.5 Locational inset and neatlines.

Univers) and a normal, consistent font size are appropriate for most maps.

Source Information and Footnotes In some large natural resource management organizations, where data development tasks are shared by multiple people, placing the names of the people who contributed to the development of a map on the map is discouraged. However, in field offices of natural resource management organizations, where field person-

Locational inset


Township and range numbers

Mt. Diablo meridian

Date: November 17, 2002 Prepared by Michael Wing

0 2 4 6 Miles - Figure 4.6 Map annotation--examples of township and range lines.

Sussex County Thinning Plan Prepared by: Pete Bettinger Date: 11/11/01

Description and Location of GIs Files Used It is common for map developers to place-in a non- descript location and using a small font size-the filenames, project names, or name of the computer code (e.g., macro) used to assist in making a map. By doing this, one can readily go back to the GIs databases of interest, or the computer code; modify an aspect of the

F i ~ r e 4.7 Description of map developer and date map composition of the map; and thus facilitate the genera- development. tion of a new version of the map. Without such guid-

ance, one may find it difficult to remember how a map was originally constructed.

2003 and you examine a map, developed in June 2002, that represents wildlife habitat across several thousand acres of a landscape. Suppose also that the habitat is a function of timber stand conditions and that you are aware that the GIs database describing timber stands was updated in December 2002. If the date is displayed on the map (June 2002), you know that the wildlife habitat being illustrated was determined using an earlier version (not the current one) of the timber inventory data.

Caveats, Disclaimers, and Warranties Increasingly, natural resource management organizations are adding more information to the maps they produce to clarify the accuracy of the location of mapped landscape features and to clarify the intended uses of the maps. This information is important in helping users understand the appropriate applications of mapped information and to help them avoid damages and injuries that might result from improper map


4

use. For example, maps have long served as vital navigational aids to mariners and pilots. The ability to pi-

I lot passengers safely depends on the quality of the map I information used as a navigational guide. Should a

I landscape landmark be misplaced or unidentified, the consequences to vehicles navigating based on erro-

I neous data could be dire. As one might imagine, there are a variety of reasons that maps should contain data- quality information, yet the current trend toward pro- viding more of this information is, at least indirectly, a function of litigation becoming more commonplace in society.

A map disclaimer is a statement that embodies the legal position of the map creator with respect to map users. Many map creators use disclaimers to distance themselves from any legal responsibility for damages that could result from the use of their maps. Caveats, similarly, warn others of certain facts in order to prevent the misinterpretation of maps. In general, caveats are less sweeping than disclaimers and may address certain portions or aspects of a map. Warranties, on the other hand, are usually written guarantees of the in- tegrity of a map and of the creator's responsibility for the repair or replacement of incorrect maps. In practice, disclaimers and caveats are used regularly, but warranties are rarely (if ever) used, in association with maps and GIs databases. Quite often, organizations add disclaimers or caveats to their maps in an attempt to warn users of the limitations of the map content. In some cases, disclaimers are noted directly on the map; in other cases, they are posted on Internet sites devoted to the distribution of maps. Pima County, Arizona, for example, provides a very thorough disclaimer about its products on an Internet site (Pima County [Arizona] Department of Transportation and Flood Control Dis- trict 2001). The main pieces of information found in caveats and disclaimers are the following:

Rights reserved via copyright and the permission requirements for modification of the map Degree of error found on the map Suitability for use Liability, or responsibility for errors or omissions (organizations usually assume no responsibility for map users misusing their maps and subsequently incurring losses) Contact points (addresses, phone numbers, e-mail addresses)

Caveats and dsclaimers vary in form and content from organization to organization. The following are four examples.

The maps on this web site were compiled by Indiana University, Indiana Geological Survey, using data believed to be accurate; however, a degree of error is inherent in all maps. The maps are distributed "AS-IS" without warranties of any kind, either expressed or

implied, including but not limited to warranties of suitability to a particular purpose or use. No attempt has been made in either the design or production of the maps to define the limits or jurisdiction of any federal, state, or local government. The maps are intended for use only at the published scale. Detailed on-the-ground surveys and historical analyses of sites may differ from the maps. (Indiana Geological Survey 2001)

Information displayed on our maps was derived from multiple sources. Our maps are only for graphic display and general planning purposes. Inquiries concerning information displayed on our maps, their sources, and intended uses should be directed to: . . . (USDI Bureau of Land Management 2001)

The Orange County Property Appraiser makes evkry effort to produce and publish the most current and accurate information possible. No warranties, expressed or implied, are provided for the data herein, its use, or its interpretation. The assessed values are NOT certified values and therefore are subject to change before being finalized for ad valorem tax purposes. OCPA's on-line (cadastral) maps are produced for property appraisal purposes, and are NOT surveys. No warranties, expressed or implied, are provided for the data therein, its use, or its interpretation. (Orange County [Florida] Property Appraiser 2001)

By reading this statement I acknowledge that the data contained in the Geographic Information System (GIs) is subject to constant change and that its accuracy cannot be guaranteed. All data is provided as is, with all faults, and without warranty of any kind, either express or implied, including, but not limited to, the implied purpose. The Town of Blacksburg does not warrant that the functions contained in the GIs data will meet requirements or that the operation of the GIs data will be uninterrupted or error free, or that the GIs data defects will be corrected. I assume the entire risk as to the quality, performance, and usefulness of the data. (Town of Blacksburg [Virginia] 2001)

The type of map that one develops will be a function of two areas of consideration: (1) the type of data (i.e., point, line, polygon, raster) contained in GIS databases and (2) the message(s) one wishes to communicate to an audience. For example, if the main GIs database used to create a map contains point features, and one wishes to illustrate the differences between the point values, one may want to show the points as dots or graduated symbols (different sizes of points based on the point attribute values). If the main GIS database used to create a map contains line features, one may want to illustrate the differences in the attributes of the lines with different line types. If the features of interest represent areas, GIS databases containing polygons

I 68 PART I Introduction to Geographic Lnformation Systems, Spatial Databases, and Map Design

- - - - 1,

CHAP~ER 4 Map Design 69

Basal area (ft2/acre)

0-20

21-120

121-175

176-230

231+

Figure 4.8 Choropleth map.

can be displayed as choropleth maps or qualitative area maps. Volumetric databases, such as digital elevation models, can be displayed as gridded fishnet maps, in perspectives, as shaded relief maps, or simply as images with different shades or colors assigned to individual pixels. Finally, if one were interested in illustrating the time dimension, one could develop maps with multiple panels, each panel containing a view of the landscape over a different time period. In some cases maps can be animated, as in a short movie, or animated to allow users to "fly through the landscape when viewed on a computer screen. The next few sections describe in more detail the most common types of maps developed in natural resource management.

Thematic Maps Thematic maps often use colors or symbols to describe the areas of a landscape. Features displayed with a combination of color and texture have been shown to be easier to find on maps than features displayed with variations in texture alone (Phillips and Noyes 1982). Thematic maps portray the spatial variation of landscape phenomena and demonstrate one variable or phenomenon at one point in time (Star and Estes 1 990).

Several types of thematic maps are common. Per- haps the most common type of thematic map is the choropleth map, on which the relative magnitude of attributes of landscape features is illustrated by a range of appropriate values (figure 4.8) and gradations of a color or a set of shading schemes that changes from an empty shaded fill to perhaps a full shaded fill (such as white to light blue to dark blue). The legend is critical when developing choropleth maps, since the colors related to the values must be explicitly described in order for map users to interpret the values. Several design aspects must be addressed when designing a legend. The


0-20

21-175

176+



1 0-20

I 21-120

121-160

161-190

191-220

rn 221-250

251+

Figure 4.9 Range of classes illustrated on a choropleth map.

number of legend classes, or categories, is an important aspect, as too few classes may not contain enough information, but too many classes may present too much detail or result in an overly "busy" map. Some- times, it is necessary to experiment with several choices to determine which works best (figure 4.9). Dent (1999) provides some guidelines related to this issue. In terms of shades, humans have difficulty in differentiating among more than 11 gray tones. As a


0-50

51-100

101-150

151-200

201+

Equal area interval

area :re)

0-20

21-120

121-175

176-230

231 +

Quantile interval

Figure 4.10 Equal interval and quantile interval legend classification.

general rule, a minimum of 4, and not more than 6, classifications should be used on a map.

The size (or ranges) of the intervals for each class also have a significant impact on a map's message. Most GIs software programs offer classification tech- niques to help create legends that take into account the distribution of the data being mapped. An equal interval legend takes into account the range of data values and creates intervals that share an equal distribution of the range (figure 4.10). A quantile distribution puts an equal number of observations into each interval. Inter- vals might also be created based on how many standard deviations an observation is from the mean or based on natural break points in the distribution of observations. Although these legend tools can save time over manual methods of creating classifications, it is advisable for map developers to examine visually the distribution of the data they are mapping to better understand its character, then decide what legend type would be useful.

Values Normal distribution

Values Random distribution

Values Even distribution

Figure 4.11 Normal, random, and even distributions of data.

Data distributions can have many shapes and associated descriptions, but among the most common are normal, random, and even distributions (figure 4.1 1) (Madej 2001). Normal distributions follow the statis- tically based representation of values that one would expect to see from most populations or population samples. For this reason, a standard deviation legend classification, with its emphasis on statistical variation from an average, works well. Random distributions are present in data groups in which one cannot discern a pattern to the occurrence of data values. Natural break points can be established by locating subgroupings of random data, creating divisions between sub-groups. Even distributions are data groups in which values do not appear to change very much; one would expect to find a relatively small standard deviation in the data values here. A quantile classificatioll works well for

I 68 PART I Introduction to Geographic Information Systems, Spatial Databases, and Map Design

Figure 4.8 Choropleth map.


1 0-20

21-120

121-175

176-230

1 231+

can be displayed as choropleth maps or qualitative area maps. Volumetric databases, such as digital elevation models, can be displayed as gridded fishnet maps, in perspectives, as shaded relief maps, or simply as images with different shades or colors assigned to individual pixels. Finally, if one were interested in illustrating the time dimension, one could develop maps with multiple panels, each panel containing a view of the landscape over a different time period. In some cases maps can be animated, as in a short movie, or animated to allow users to "fly through" the landscape when viewed 011 a computer screen. The next few sections describe in more detail the most common types of maps developed in natural resource management.

Thematic Maps Thematic maps often use colors or symbols to describe the areas of a landscape. Features displayed with a combination of color and texture have been shown to be easier to find on maps than features displayed with variations in texture alone (Phillips and Noyes 1982). Thematic maps portray the spatial variation of landscape phenomena and demonstrate one variable or phenomenon at one point in time (Star and Estes 1 990).

Several types of thematic maps are common. Per- haps the most common type of thematic map is the choropleth map, on which the relative magnitude of attributes of landscape features is illustrated by a range of appropriate values (figure 4.8) and gradations of a color or a set of shading schemes that changes from an empty shaded fill to perhaps a full shaded fill (such as white to light blue to dark blue). The legend is critical when developing choropleth maps, since the colors related to the values must be explicitly described in order for map users to interpret the values. Several design aspects must be addressed when designing a legend. The


G 0-20

21-175

11 176+


0 0-20

m 21-120

121-175

111111 176-230

1 231+


1 0-20

E 21-120

121-160

161-190

191-220

221-250

251+

Figure 4.9 Range of classes illustrated on a choropleth map.

number of legend classes, or categories, is an important aspect, as too few classes may not contain enough information, but too many classes may present too much detail or result in an overly "busy" map. Some- times, it is necessary to experiment with several choices to determine which works best (figure 4.9). Dent (1999) provides some guidelines related to this issue. In terms of shades, humans have difficulty in differentiating among more than 11 gray tones. As a


( 0-50

51-100

101-150

151-200

1 201+

Equal area interval


0 0-20

a 21-120

121-175

176-230

231+

Quantile interval

Figure 4.10 Equal interval and quantile interval legend classification.

general rule, a minimum of 4, and not more than 6, classifications should be used on a map.

The size (or ranges) of the intervals for each class also have a significant impact on a map's message. Most GIs software programs offer classification tech- niques to help create legends that take into account the distribution of the data being mapped. An equal interval legend takes into account the range of data values and creates intervals that share an equal distribution of the range (figure 4.10). A quantile distribution puts an equal number of observations into each interval. Inter- vals might also be created based on how many standard deviations an observation is from the mean or based on natural break points in the distribution of observations. Although these legend tools can save time over manual methods of creating classifications, it is advisable for map developers to examine visually the distribution of the data they are mapping to better understand its character, then decide what legend type would be useful.

- - -- -


Values Normal distribution

Values Random distribution

Values Even distribution

Figure 4.11 Normal, random, and even distributions of data.

Data distributions can have many shapes and associated descriptions, but among the most common are normal, random, and even distributions (figure 4.11) (Madej 2001). Normal distributions follow the statis- tically based representation of values that one would expect to see from most populations or population samples. For this reason, a standard deviation legend classification, with its emphasis on statistical variation from an average, works well. Random distributions are present in data groups in which one cannot discern a pattern to the occurrence of data values. Natural break points can be established by locating subgroupings of random data, creating divisions between sub-groups. Even distributions are data groups in which values do not appear to change very much; one would expect to find a relatively small standard deviation in the data values here. A quantile classification works well for

70 PART I Introduction to Geographic Information Systems, Spaha1 Databases, and Map Design CHAPTER 4 Map Design 71


( 0-50

51-100

101-150

151-210

200+


L1 0-50 Figure 4.13 Contour map.

51-100 I

Scottsburg

Digital elevation model

Elevation (feet)

! 101-1 50 can be categorized into more than one class, the classes 1 151 -21 0 are overlapping. Alternatively, the characteristics of I 1 506-605 I I

landscape features might not fall into any class (might be omitted from a map) because the values fall-into a classification level "gap." Either way, the . potential problems with the classification must be addressed.

With the increasing capabilities and affordability

0 5000 10,000 Feet - Prepared by: Michael Wing Last updated: November 17,2002 DEM resolution: 98 ft

of color printers and plotters, the use of color to por- I $1

tray legend classifications graphically in maps has Figure 4.14 Raster map. Basal area (ft2/acre)

0-50

51-100

rn rn 1 220+

become standard. In general, tonal progressions of a single color are useful for illustrating magnitudes of change, with the lighter color tones indicating a lesser quantity of an attribute value than the darker tones.

represented with data values may be those that represent P V P ~ V 500-fnnt rhanoe in elevntinn

I - -A A - - . --, - - - A - - - -A - -A A -A - . - -A - -a.

1 101-150 The same effect can be generated with gray tones. Until now, this discussion has focused on maps 1 51 -21 Single-color progressions are particularly helpful for eenerated usine vector GIS databases. but raster-based

continuous numeric variables. For nominal data classifications, such as ownership or land use, or numeric

o----- ~- - - . . ~ - - - - - . .....- - ~ - - - , - - - - - - - - - - - -

maps are also important for displaying data stored in

Figure 4.12 Range of criteria used for a choropleth map, with nv~rlannino rlaccnc (tnnl rnncictont int~rvslr ,,.... ",--." yy..-* .,...""'" \Ivy/, -"..Y.Y.I..I I.. I-. I"."

(middle), and omitted classes (bottom).

even distributions, as equal numbers of observations are placed in each category.

Regardless of how legend intervals are created, map developers need to ensure that the intervals are consistent and make sense from an interpretation point of view. This also includes verifying that legend classifications are nonoverlapping and nonomitting (figure 4.12). If the characteristics of landscape features

similar features are used to emphasize gradients or distributions, such as elevations or precipitation levels across a landscape (Star and Estes 1990). The contour interval is the distance between adjacent contour lines. The choice of an interval is important when creating contour maps: tight intervals may result in a cluttered map; wide intervals might misrepresent landscape variation. To reduce clutter on maps, not every contour interval is described with a data value-only those representing significant changes in contour, usually denoted themselves by an interval. For example, although the contour interval between adjacent contour lines may be 100 feet, the only contour lines

LIIua, bbllblullr IIIVIb I1bLbl~geneity across a landscape (figure 4.14).

Dot Density Maps and Cartogra Dot density maps (figure 4.15) were once commonly BlgUre 4.13 Dot density

used in natural resource management, although less so now. Each dot in a dot density map represents a given value of an attribute. Thus, areas with a greater density of dots are meant to represent areas with greater values of landscape features can be viewed. These maps are of a particular attribute. Graduated circle maps scale also fairly uncommon, given the clutter that can be the diameters of circle shapes proportionately to an at- generated over large landscape areas and the high den- tribute's value to demonstrate differences. Cartograms sity of landscape features displayed within a given area (figure 4.16) are maps in which more than one attribute (e.g., a multitude of small po ly~

70 PART I Introduction to Geographic Information Systems, Spatial Databases, and Map Design CHAPTER 4 Map Design 71

,

Figure 4.13 Contour map.

landscape features might not fall into any class (might be omitted from a map) because the values fall into a classification level "gap." Either way, the .

5000 10,000 Feet Prepared by. Mlchael Wlng potential problems with the classification must be - Last updated November 17,2002 addressed. DEM resolut~on: 98 ft

With the increasing capabilities and affordability of color printers and plotters, the use of color to portray legend classifications graphically in maps has Figure 4.14 Raster map.

become standard. In general, tonal progressions of a single color are useful for illustrating magnitudes of change, with the lighter color tones indicating a lesser represented with data values may be those that repre- quantity of an attribute value than the darker tones. sent every 500-foot change in elevation.

101-150 The same effect can be generated with gray tones. Until now, this discussion has focused on maps 151 -21 Single-color progressions are particularly helpful for generated using vector GIs databases, but raster-based

continuous numeric variables. For nominal data classi- maps are also important for displaying data stored in fications, such as ownership or land use, or numeric the raster GIs data structure. These maps are very sim- data with only a few categories, distinctly different ilar to choropleth maps: map developers must classify colors or patterns can be used to make certain cate- the values held by the raster pixels, then display them gories stand out on a map. on a map using a legend. Raster-based maps, unless

Contour maps (figure 4.13) are also a type of the- created by rasterizing a vector GIs database, usually matic map and are sometimes called isoline or isarith- have a fuzzier appearance than vector-based maps and, mic maps; on these maps, lines or other collections of thus, generally represent more heterogeneity across a similar features are used to emphasize gradients or dis- Figure 4.12 Range of criteria used for a choropleth map, landscape (figure 4.14).

with overlapping classes (top), consistent intervals tributions, such as elevations or precipitation levels (middle), and omitted classes (bottom). across a landscape (Star and Estes 1990). The contour

interval is the distance between adjacent contour lines. Dot Density Maps and Cartograms The choice of an interval is important when creating Dot density maps (figure 4.15) were once commonly Figure 4-15

even distributions, as equal numbers of observations contour maps: tight intervals may result in a cluttered used in natural resource management, although less so are placed in each category. map; wide intervals might misrepresent landscape now. Each dot in a dot density map represents a given

Regardless of how legend intervals are created, variation. To reduce clutter on maps, not every contour value of an attribute. Thus, areas with a greater density map developers need to ensure that the intervals are interval is described with a data value-only those of dots are meant to represent areas with greater values of landscape features can be viewed. These maps are consistent and make sense from an interpretation point representing significant changes in contour, usually of a particular attribute. Graduated circle maps scale also fairly uncommon, given the clutter that can be of view. This also includes verifying that legend clas- denoted themselves by an interval. For example, al- the diameters of circle shapes proportionately to an at- generated over large landscape areas and the high den- sifications are nonoverlapping and nonomitting (fig- though the contour interval between adjacent con- tribute's value to demonstrate differences. Cartograms sity of landscape features displayed within a given area ure 4.12). If the characteristics of landscape features tour lines may be 100 feet, the only contour lines (figure 4.16) are maps in which more than one attribute (e.g., a multitude of small polygons).


Timber Harvest and Management Plan Map

Daniel Pickett Forest - Unit 15

Stand attribute

Basal area per acre

( Volume per acre (MBF)

Figure 4.19 Figure-ground relationship demonstrated by forest stands. Three stands are emphasized from neighboring stands by altering their appearance through line thickness and

1 shading.

I ...m....... Streams Harvest area I Figure 4.16 Cartogram. - Roads $ Log decks/Landings

Stand boundaries Gates

2000 ft 0 4000 ft 8000 ft

fi 1 inch = 4000 feet

Title of map North arrow Develop y

Unit 15 Harvest Plan Daniel Pickett Forest Prepared by: Pete Bettinger Not for Distribution Date: 11/11/01 c:\Pickett\Unit-15-plan.apr

1 1 Map preparer, etc.

b.

Figure 4.18 Visual contrast. The lighter contrast of map (a) does not draw a viewer's attention as strongly as does map (b).

Edit acceptable?

Figure 4.21 Final map.

Title of map 7 of illustrative concerns (showing the correct information), and time constraints (the time remaining before a deadline). It is advisable to start this process by first developing some handwritten notes or bullets that contain the main ideas about the intended map message(s) or purpose and the type of audience likely to view the map. Once these concepts have been identified, it might also be worthwhile to create a hand sketch of the basic map components and how they fit together. At this point, the development of the map within GIs can begin. A well-developed, visually centered map is a re- flection of one's professionalism as a natural resource manager (figure 4.21).

within their map products. Visual contrast is the most important graphic factor in creating a map (Robinson et al. 1995) and is what sets an object apart from a background (figure 4.18). Sizes, shapes, textures, and colors can all be used to introduce contrast into a map. Contrast will focus the attention of an observer and plays a strong role in determining the clarity and sharpness of a map from the observer's perspective. Map developers must also balance figure-ground relationships, so that the important objects of a map are separated from those that are considered ancillary. In human perception, figures are the objects that are most strongly perceived and remembered, whereas data are less distinctive and less memorable (Dent 1999). Tech- niques such as figure closure, contrasts with other objects, and object grouping can be used to establish distinctive ground-figure relationships (figure 4.19). Visual balance is affected by the size of the symbols and features, as well as the location of these in relation to the visual center of the map (figure 4.20). Each

Landscape I I completed I Map 1 1 Legend 1

Figure 4.17 Design loop.

Scale bar ~ Map preparer, etc.

Maps usually go through more than one version before they are used by map customers, whether changes are needed based on the map developer's visual assess- ment of the map or based on customers' suggestions (figure 4.17). Feedback from supervisors and coworkers will allow one to fine-tune maps for reports or ac- tivity plans. Besides the aesthetic concerns regarding map type, number of classes shown, and type of scale, map developers should strive to achieve visual balance

Figure 4.20 Visual balance of a map.

There are a number of mistakes, oversights, and omis- iteration in the development of a map can be con- sions that can impair a map's ability to deliver the de- sidered one iteration in the design loop. The number of veloper's intended message to an audience. Probably iterations of a design loop will be a function of the most important aspect of creating a map is to deter- one's ability to address a range of visual concerns mine the audience that will be viewing the map. If (visual contrasts, visual balance, legend, etc.), a range one's coworkers (other foresters, biologists, etc.) will

li~l 'r 72 PART I lntroduct~on to Geographic Information Sy\tems, Spatial Database\, and Map Design CHAPTER 4 Map Design 73

-

Timber Harvest and Management Plan Map

Daniel Pickett Forest - Unit 15

Legend:

........... Streams Harvest area

- Roads @ Log deckslLandings

Stand boundaries +-+ Gates

2000 ft 0 4000 ft 8000 ft

1 Inch = 4000 feet

Unit 15 Hawest Plan Daniel Pickett Forest Prepared by: Pete Bett~nger Not for Distribution Date: 11/11/01 c:\PickeNUnit-15-plan.apr

Figure 4.19 Figure-ground relationship demonstrated by forest stands. Three stands are emphasized from neighboring stands by altering their appearance through line thickness and shading.

Stand attr~bute

Basal area per acre

Volume per acre (MBF)

Figure 4.16 Cartogram.

Title of map North arrow Develop

map

Get feedback

-

Landscape

I Map preparer, etc. I I F'igure 4.21 Final map.

Figure 4.18 Visual contrast. The lighter contrast of map (a) does not draw a viewer's attention as strongly as does map (b). c N 0 acceptable? ]II

Title of map 1 of illustrative concerns (showing the correct information), and time constraints (the time remaining before a deadline). It is advisable to start this process by first r r r ; t h ; n thAr m n - -r-rl..nto TT;olxnl ---'rast is the most WlLlllll L11bll I l l u p pluuuLLD. VlDU'll LUllL

important graphic factor in creating a I

et al. 1995) and is what sets an objec background (figure 4.18). Sizes, shape colors can all be used to introduce cant Contrast will focus the attention of a1 plays a strong role in determining t sharpness of a map from the observer Map developers must also balance figu~ tionships, so that the important object: separated from those that are considered ancillary. In human perception, figures are the objects that are most strongly perceived and remembered, whereas data are less distinctive and less memorable (Dent 1999). Tech- niques such as figure closure, contrasts with other objects, and object grouping can be used to establish distinctive ground-figure relationships (figure 4.19). Visual balance is affected by the size of the syn~bols and features, as well as the location of these in relation to the visual center of the map (figure 4.20). Each

&I completed

Landscape I developing some handwritten notes or bullets that contain the main ideas about the intended map message(s) or purpose and the type of audience likely to view the map. Once these concepts have been identified, it might also be worthwhile to create a hand sketch of the basic map components and how they fit together. At this point, the development of the map within GIs can begin. A well-developed, visually centered map is a re- flection of one's professionalism as a natural resource

, P. A n * \

1113-

nap La" uc LUII- 51u11s LllaL L ~ I I I I ~ I ~ ~ I I i2 111ilp 5 i l u l l l ~ y LU UGIIVCI LIIC de- ~p. The number of veloper's intended message to an audience. Probably be a function of the most important aspect of creating a map is to deter- ' visual concerns mine the audience that will be viewing the map. If

- :nd, etc.), a range one's coworkers (other foresters, biologists, etc.) will

map (Robinson :t apart from a s, textures, and rast into a map. n observer and he clarity and -'s perspective. -e-ground rela- ; of a map are

I Legend 1 Figure 4.17 Design loop.

I Scale bar I Mao orenarer. etc

I ' .~ -.,. r. -r -. -. , -

I manager (rigure 4 . ~ I ).

Maps usually go through more than one version before they are used by map customers, whether changes are needed based on the map developer's visual assess- ment of the map or based on customers' suggestions (figure 4.17). Feedback from supervisors and coworkers will allow one to fine-tune maps for reports or ac- tivity plans. Besides the aesthetic concerns regarding map type, number of classes shown, and type of scale, map developers should strive to achieve visual balance

Figure 4.20 Visual balance of a map. COMMON MAP PROBLEMS There are a number of mistakes, oversights, and o r ; -

iteration in the development of a r---- - - - - " - --- &L-6 --- :---:.. - ---?" "L:l:*-. 4- 2-1: -.-- 4L- sidered one iteration in the design loc iterations of a design loop will t one's ability to address a range of (visual contrasts, visual balance, 1e.s


be the primary audience, then perhaps the basic map elements (e.g., a north arrow, bar scale, or locational inset) are not required. This audience may expect to see, instead, more technical information, such as annotation or other descriptive information related to landscape features that demonstrate variation across the landscape. If the audience is a general one, and not familiar with the landscape resources on the map, then it might be important to include basic map elements (e.g., a north arrow, scale bar, and inset) that help the audience orient themselves to the map. If the audience is a scientific one, they may also want so see more detail in the data values, as well as other map guides. Map problems are usually the result of leaving a key element, such as a scale, off a map. Sometimes, these problems result from misjudging the audience; other times, it is simply a matter of oversight. For example, since automatic spell checking processes are available in most word-processing software, map producers sometimes forget that spell checking is usually a manual operation for most GIs map development processes. This requires that map producers carefully read all map text before presenting the final product to their customers.

Excessive detail or clutter can also detract from a map's message and intent. Most GIs software programs feature an impressive array of mapmaking symbols and tools capable of producing any number of cartographic symbols and other aids. Although many of these tools can be quite helpful, too many objects on a map produce clutter. Excessive detail, especially in maps that are intended to be general information dis- plays, can also result when map developers insert too much text (annotation or labels) onto a map.

It is also common that the output device (e.g., printer or plotter) produces a map with colors that appear slightly different from what the map developer assumes by viewing the computer screen. These problems can be very frustrating, especially after one has painstakingly put together a colored legend scheme and subsequently must make adjustments once a map has been produced. Sometimes, a color mismatch problem can be addressed by choosing a color palette file that is compliant with the output device. Other solutions include using only the primary colors (red, blue, green) or subtractive colors (magenta, cyan, yel- low) and creating color schemes that take plotter trans- lations of monitor colors closely into account.

USGS 7.5 MINUTE SERIES QUADRANGLE MAPS The most comprehensive reference maps in the United States, in terms of scale and geographic extent, are published, by the U.S. Geological Survey (USGS).

These maps cover the entire United States, are published at several different scales, contain a wealth of information, and, very important for GIs projects, are available as digital databases that can be used by most GIs software programs that have raster display capabilities. The most detailed of the maps produced by the USGS are the 7.5 Minute (7.5') Series Quadrangle maps, which have a published map scale of 1 :24,000. The 7.5' refers to the total amount of latitude and longitude, in degrees, on the Earth's surface that each Quadrangle represents. In some cases, features from the Quadrangle maps, such as hydrography or roads,

-

may be available in a vector format as a digital line graphic (DLG). These Quadrangle maps are a great resource for those who want to learn more about a landscape, and they serve as very useful templates for digitizing or creating GIs databases.

Given the broad availability of the 7.5' maps, their cartographic detail, and their popularity as a GIs database template for forestry and natural resource applications, we will examine one of these maps and some of the more noteworthy components. Although we will focus on an example using the Corvallis Quadrangle from Oregon, its features should be available on most other 7.5' maps. In particular, one should look closely at the information that appears at the bottom of the map (figure 4.22). Quadrangle maps also provide information printed along the top margin of the map, but this is generally much more limited and a subset of what one finds along the bottom margin of the map. At the time this book was being developed, a digital copy of this Quadrangle could be downloaded from http://www.reo.gov/gis/gisdata.htm/.

Lower Right-Hand Corner The lower right-hand comer of the Corvallis Quad- rangle (figure 4.23) contains a representative scale (1 :24,000) and several scale bars with units expressed in miles, feet, and meters. Information is also provided for two contour intervals: the main contour interval of 20 feet (shown by solid lines on the map's surface) and a secondary contour interval of 5 feet (represented by dashed lines). The reason for this dual depiction is that the Corvallis Quadrangle includes a mixture of mod- erately sloped forested areas and relatively flat areas where urban and agricultural development has oc- curred; the dashed 5-foot contours are used for the flatter areas. Below the contour interval descriptions, there is information about where to purchase hard- copies of the Corvallis Quadrangle and the availability of topographic map and symbol descriptions. 'On the right, a graphic can be found that indicates the location of the Quadrangle relative to the Oregon State border. Below this graphic, some text clarifies that the purple areas of the map were updated with aerial photography


be the primary audience, then perhaps the basic map These maps cover the entire United States, are pub- elements (e.g., a north arrow, bar scale, or locational lished at several different scales, contain a wealth of inset) are not required. This audience may expect to information, and, very important for GIs projects, are see, instead, more technical information, such as anno- available as digital databases that can be used by most tation or other descriptive information related to land- GIs software programs that have raster display capa- scape features that demonstrate variation across the bilities. The most detailed of the maps produced by the landscape. If the audience is a general one, and not fa- USGS are the 7.5 Minute (7.5') Series Quadrangle miliar with the landscape resources on the map, then it maps, which have a published map scale of 1:24,000. might be important to include basic map elements The 7.5' refers to the total amount of latitude and (e.g., a north arrow, scale bar, and inset) that help the longitude, in degrees, on the Earth's surface that each audience orient themselves to the map. If the audience Quadrangle represents. In some cases, features from is a scientific one, they may also want so see more de- the Quadrangle maps, such as hydrography or roads, tail in the data values, as well as other map guides. may be available in a vector format as a digital line Map problems are usually the result of leaving a key graphic (DLG). These Quadrangle maps are a great element, such as a scale, off a map. Sometimes, these resource for those who want to learn more about a problems result from misjudging the audience; other landscape, and they serve as very useful templates for times, it is simply a matter of oversight. For example, digitizing or creating GIs databases. since automatic spell checking processes are avail- Given the broad availability of the 7.5' maps, their able in most word-processing software, map produc- cartographic detail, and their popularity as a GIs data- ers sometimes forget that spell checking is usually a base template for forestry and natural resource appli- manual operation for most GIs map development cations, we will examine one of these maps and some processes. This requires that map producers carefully of the more noteworthy components. Although we will read all map text before presenting the final product to focus on an example using the Corvallis Quadrangle their customers. from Oregon, its features should be available on most

Excessive detail or clutter can also detract from a other 7.5' maps. In particular, one should look closely map's message and intent. Most GIs software pro- at the information that appears at the bottom of the grams feature an impressive array of mapmaking sym- map (figure 4.22). Quadrangle maps also provide in- bols and tools capable of producing any number of formation printed along the top margin of the map, but cartographic symbols and other aids. Although many this is generally much more limited and a subset of of these tools can be quite helpful, too many objects on what one finds along the bottom margin of the map. a map produce clutter. Excessive detail, especially in At the time this book was being developed, a digital maps that are intended to be general information dis- copy of this Quadrangle could be downloaded from plays, can also result when map developers insert too http://www.reo.gov/gis/gisdata.htm/. much text (annotation or labels) onto a map.

It is also common that the output device (e.g., printer or plotter) produces a map with colors that Lower Right-Hand Corner appear slightly different from what the map developer The lower right-hand corner of the Corvallis Quad- assumes by viewing the computer screen. These prob- rangle (figure 4.23) contains a representative scale lems can be very frustrating, especially after one has (1:24,000) and several scale bars with units expressed painstakingly put together a colored legend scheme in miles, feet, and meters. Information is also provided and subsequently must make adjustments once a map for two contour intervals: the main contour interval of has been produced. Sometimes, a color mismatch 20 feet (shown by solid lines on the map's surface) and problem can be addressed by choosing a color palette a secondary contour interval of 5 feet (represented by Figure 4.22 Corvallis Quadrangle with neatlines around map areas to be described in detail. file that is compliant with the output device. Other dashed lines). The reason for this dual depiction is that solutions include using only the primary colors (red, the Corvallis Quadrangle includes a mixture of mod- blue, green) or subtractive colors (magenta, cyan, yel- erately sloped forested areas and relatively flat areas captured in 1982 (and hence edited in 1986). Moving 1995). Each block of latitude and longitude can con- low) and creating color schemes that take plotter trans- where urban and agricultural development has oc- to just below the bottom right-hand corner of the map, tain up to 64 7.5' Quadrangle maps that comprise an lations of monitor colors closely into account. curred; the dashed 5-foot contours are used for the one finds a legend for road map symbols. The name of eight-by-eight matrix. Letters are used from A to H to

flatter areas. Below the contour interval descriptions, the map is listed (CORVALLIS, OREG.), and the map denote rows starting from the comer of the latitude and there is information about where to purchase hard- is described as the bottom right-hand comer (SE14) of longitude intersection and moving upward. Numbers

USGS 7.5 MINUTE SERIES copies of the Corvallis Quadrangle and the availability the 15' Corvallis Quadrangle. The OHIO code descrip- are used from 1 to 8, moving westward to signify

QUADRANGLE MAPS of topographic map and symbol descriptions. On the tion, sometimes referred to as the USGS Map Refer- columns. Thus, the Corvallis Quadrangle is located in right, a graphic can be found that indicates the location ence Code, is listed as 44123-E3. This means that the the matrix at the intersection of the 5th row and the 3rd

The most comprehensive reference maps in the United of the Quadrangle relative to the Oregon State border. map is located in a block of geographic latitude and column (figure 4.24). This OHIO code system is used States, in terms of scale and geographic extent, are Below this graphic, some text clarifies that the purple longitude that begins at the intersection of 44" latitude by many map distributors to identify the relative loca- published by the U.S. Geological Survey (USGS). areas of the map were updated with aerial photography and 123" longitude (USDI U.S. Geological Survey tion of quadrangles. The year of the original aerial

76 PART I Introduction to Geographic Information Systems, Spatial Databases, and Map Design I

CONTOUR INTERV DOTTED LINES REPRESENT 5 FOOT CONTOURS

NATIONAL GEODETIC VERTICAL DATUM OF 1929

CORVALLIS, OREG. QUADRANGLE LOC*MN

THIS MAP COMPLIES WITH NATIONAL MAP ACCURACY STANDARDS SEM MRVALUS 15 WADRANOLe

FOR SALE BY U S GEOLOGICAL SURVEY DENVER COLORADO 8 0 2 2 5 . 0 R RESTON VlROlNlA 2 2 0 9 2 ~ ~ ~ , " ~ ~ ~ ~ ~ ~ ~ ~ $ ~ ~ ~ ~ ~ ~ c ~ ~ $ ~ ' 44123 E3-TF-024

A FOLDER DESCRIBING TOPOORAPHIC MAPS AND SYMBOLS IS AVAILABLE ON REQUEST Thrs niormatlcn not fteld c h e w Map edited 1986

D I M IS73 8 B M E R l E S V802

Figure 4.23 Lower right-hand corner of the Corvallis Quadrangle.

photography (1969) that was used to create the map is the U.S. Coast and Geodetic Survey, and the State of listed, as is the last revision year (1986). The bottom Oregon. Mapped surfaces were taken from 1967 aerial comer of the mapped area has a set of geographic co- photography and were field checked in 1969. Projec- ordinates (44'30' and 123"15'), which describe its lo- tion information is then listed, and the base surface is cation. Just to the east and slightly north of this comer, described as a polyconic projection, NAD27, using the a cross appears. These crosses are in similar locations Oregon State Plane North Coordinate System. A line relative to all four mapped area corners and demon- follows, which describes the coloring of the UTM co- strate how the mapped surface comers can be adjusted ordinates listed around the perimeter of the map and to switch the datum of the map's projection from the UTM zone (10) that was used. Instructions for con- NAD27 to NAD83 (NAD is short for North American verting the mapped surface from NAD27 to NAD83 Datum). A full universal transverse Mercator (UTM) are also given. This information is useful for potential easting (479,000 m) is found just west of this corner coordinate conversions in a GIs. In addition, text de- and a full UTM northing (4,928,000 m) to the north. scribes that only landmark buildings are shown in map Full UTM coordinates are also given along the oppo- areas that are tinted red. Landmark buildings are those site map comer. Hash marks extending outward from that serve the public, have cultural or historical signif- the mapped area indicate the location on these coordi- icance, or are unusually large in relation to surround- nates relative to the rest of the map. These hash marks ing buildings. continue around the entire perimeter of the map's sur- To the right of these statements, a graphic of the face, but the last three digits of the eastings and north- map's orientation to several definitions of north is ings that accompany the marks are not printed. shown, and text below the graphic explains that the

orientation is from the map's center. The longest north line is topped by a star symbol and refers to astronomic

Lower Left-Hand Corner north. The line to the left of astronomic north refers The lower left-hand comer of the map (figure 4.25) to grid north (GN) and is oriented 0°13' (0.22") west states that the map was produced by the USGS with of astronomic north. Grid north is the direction in control or reference points established by the USGS, which the Oregon State Plane Coordinate System is

Figure 4.24 OHIO code location of the Corvallis Quadrangle.


-

referenced. The line to the right of astronomic north shows the magnetic declination (19"), relative to astronomic north, that existed in 1986. Since magnetic north can fluctuate from year to year (small daily shifts are also possible), the date of the measurement is important for those who wish to convert their data to match the map's projection.

Geographic coordinates appear at the corner of the mapped surface, and the UTM coordinate abbrevia- tions are listed. A full listing of state plane coordinates (NAD27) appears and is marked by hatch lines to

the north (320,000 feet) and east (1,260,000 feet) of this comer. Full state plane coordinates are also listed along the upper right-hand comer. Unmarked hash marks around the rest of the map's perimeter denote gradations of the state plane coordinates. Periodically, range and township divisions appear as longer dashed lines on the map's surface. Along the latitudinal axis of figure 4.25, one can see R. 6 W. and R. 5 W. This sig- nifies the division between Range 6 and 5, west of the reference meridian (Willamette) that was used for creating the Public Land Survey System (PLSS, described

76 PART I Introduction to Geographic Information Systems, Spatial Databases, and Map Design I CHAPTER 4 Map Design 77

1 1 HlLL I----,

lma o ma aa, aam ma e m morrrr Primary h~ghway, all weather Llght duty road all weather 5-j?~

* - - - hard surface - lmproved surface - - ,. 7,

1 5 0 I KILOMETER t l t - - - r - . . Semndary h~ghway all weather Un~mprwed road, fair or dry

hard surface - weather . . .=. . . . CONTOUR INTERVAL 20 FEET

OOTTED LINES REPRESENT 5 FOOT CONTOUR5 0 U s Route 0 State Route NATIONAL GEODETIC VERTICAL DATUM OF 1929 OREGON

CORVALLIS. OREG. 9UAORANGLE LOUTON SE/4 WRVILUS 15. OUAORANOLE

THIS M A P COMPLIES WITH NATIONAL MAP ACCURACY STANDARDS 44122E3-TF024 FOR SALE BY U. S. GEOLOGICAL SURVEY. DENVER. COLORADO 80225. OR RESTON. VIRGINIA 22092 ~~~~~~~~8~ ~ ~ $ e a ~ ~ ~ ~ ~ ~ ~ s ~ , " , " ~ '

A FOLDER DESCRIBING TOPOGRAPHIC MAPS AND SYMBOLS IS AVAILABLE ON REQUEST This nformatlcn not fleld checkffi. Map edited 1986 1969 PHOTOREVISED 1986

Figure 4.23 Lower right-hand corner of the Corvallis Quadrangle.

photography (1969) that was used to create the map is listed, as is the last revision year (1986). The bottom corner of the mapped area has a set of geographic coordinates (44'30' and 123"15'), which describe its location. Just to the east and slightly north of this corner, a cross appears. These crosses are in similar locations relative to all four mapped area corners and demonstrate how the mapped surface corners can be adjusted to switch the datum of the map's projection from NAD27 to NAD83 (NAD is short for North American Datum). A full universal transverse Mercator (UTM) easting (479,000 m) is found just west of this corner and a full UTM northing (4,928,000 m) to the north. Full UTM coordinates are also given along the oppo- site map corner. Hash marks extending outward from the mapped area indicate the location on these coordinates relative to the rest of the map. These hash marks continue around the entire perimeter of the map's surface, but the last three digits of the eastings and north- i n g ~ that accompany the marks are not printed.

Lower Left-Hand Corner The lower left-hand corner of the map (figure 4.25) states that the map was produced by the USGS with

the U.S. Coast and Geodetic Survey, and the State of Oregon. Mapped surfaces were taken from 1967 aerial photography and were field checked in 1969. Projec- tion information is then listed, and the base surface is described as a polyconic projection, NAD27, using the Oregon State Plane North Coordinate System. A line follows, which describes the coloring of the UTM coordinates listed around the perimeter of the map and the UTM zone (10) that was used. Instructions for con- verting the mapped surface from NAD27 to NAD83 are also given. This information is useful for potential coordinate conversions in a GIs. In addition, text describes that only landmark buildings are shown in map areas that are tinted red. Landmark buildings are those that serve the public, have cultural or historical signif- icance, or are unusually large in relation to surround- ing buildings.

To the right of these statements, a graphic of the map's orientation to several definitions of north is shown, and text below the graphic explains that the orientation is from the map's center. The longest north line is topped by a star symbol and refers to astronomic north. The line to the left of astronomic north refers to grid north (GN) and is oriented 0°13' (0.22") west of astronomic north. Grid north is the direction in

Figure 4.24 OHIO code location of the Corvallis Quadrangle.

referenced. The line to the right of astronomic north shows the magnetic declination (19"), relative to astronomic north, that existed in 1986. Since magnetic north can fluctuate from year to year (small daily shifts are also possible), the date of the measurement is important for those who wish to convert their data to match the map's projection.

Geographic coordinates appear at the corner of the mapped surface, and the UTM coordinate abbrevia- tions are listed. A full listing of state plane coordinates (NAD27) appears and is marked by hatch lines to

the north (320,000 feet) and east (1,260,000 feet) of this corner. Full state plane coordinates are also listed along the upper right-hand corner. Unmarked hash marks around the rest of the map's perimeter denote gradations of the state plane coordinates. Periodically, range and township divisions appear as longer dashed lines on the map's surface. Along the latitudinal axis of figure 4.25, one can see R. 6 W. and R. 5 W. This sig- nifies the division between Range 6 and 5, west of the reference meridian (Willamette) that was used for creating the Public Land Survey System (PLSS, described

78 PART I Introductioil to Geographic Information Systems, Spatial Databases, and Map Design I CHAPTER 4 Map Design 79

, Mapped, edited, and published by the Geological Survey

,of& Control by USGS, USC&GS, and State of Oregon +"+' $ ,& Topography by photogrammetric methods from aerial 6 photographs taken 1967. Field checked 1969

Polyconic project~on. 1927 North Arnertcan datum 10,000-foot grid based on Oregon coord~nate system, north zone 1000-meter Universal Transverse Mercator g r~d tlcks, zone 10, shown In blue

To place on the predicted North American Datum 1983, move the ~rojection lines 23 meters north and

UTM GRID AND 1986 MAGNETIC NORTH DECLINATION AT CENTER OF SHEET

96 meterr eak as shown by dashed comer ticks

There may be private inholdings within the boundaries of the National or State reservations shown on this map

Red tint indicates areas in which only landmark buildings are shown

Figure 4.25 Lower left-hand corner of the Corvallis Quadrangle.

in chapter 2) for Oregon. Larger numbers appear on country in a grid of townships (approximately 6-by-6- the mapped surface and describe the boundaries be- mile blocks created by the intersections of township tween sections and donation land claims (DLCs). Most and range lines) that were created from a reference of the western United States was originally divided ac- meridian, with townships further divided into sec- cording to the PLSS. The PLSS split regions of the tions measuring approximately 1 square mile. Section

rigorous land measurement systems that superceded the PLSS. Through these systems, settlers could stake claims to lands, and these systems were generally referred to as DLCs. DLC boundaries are numbered starting with 37.

In general, green shading (gray in the black-and- white image of figure 4.25) is used to represent forested or natural areas, and no shading is used to represent developed areas. Roads, streams, and other cultural and natural landscape features are also visible throughout the map.

National Map Accuracy Standards According to the information illustrated in figure 4.23, the Corvallis Quadrangle map complies with the Na- tional Map Accuracy Standards (NMAS). These standards were originally developed by the U.S. Bureau of the Budget in 1941, so that guidelines would be available for the establishment of horizontal and vertical map accuracy at multiple scales. The guidelines were also intended to help protect and inform consumers about the quality of the map products they acquired. The guidelines assume that organizations that claim adherence to NMAS guidelines are responsible for en- suring compliance. The NMAS was last revised in 1947 (Thompson 1979).

The guidelines (figure 4.26) provide horizontal accuracy standards for map scales larger than 1:20,000 and for scales at 1:20,000 or smaller. For the larger map scales, no more than 10 percent of the points ver- ified shall be in error by 1130th of an inch, as measured on the map surface. For smaller scale maps, this tolerance is 1150th of an inch. The Corvallis Quadrangle falls into the latter category. To test for NMAS compliance, locations or elevations from map points are compared with their actual measurements, where locations or elevations have been derived by highly accurate ground surveys. Within these comparisons, only 10 percent of the points can be in error by more than

. the tolerance. Table 4.1 describes the tolerances in

Scale Standard (Feet)

relation to some of the more common map scales. For the Corvallis Quadrangle, this threshold would be 40 feet, indicating that not more than 10 percent of the tested map points should differ from their actual locations by more than 40 feet. Vertical accuracy standards are applied by using half the contour interval as a benchmark. For vertical accuracy of the primary contour lines (20' intervals) of the Corvallis Quadrangle, the standard indicates that 90 percent of the elevation points checked along the contour lines should not be in error by more than 10 feet.

Typically, on USGS 7.5 Minute Quadrangles, 28 points are examined for accuracy verification, representing a very small portion of the population of map points. It is also worth noting that these points are not randomly selected but, rather, represent locations that are readily visible on the photography from which the map was created, such as road intersections, bridges, and other noteworthy structures. Thus, one would expect that the points represent the mapped areas where the photogrammetric methods used to create the map were most reliable. It is also worth noting that 10 percent of those points could be off by any distance, and the resulting map would still be NMAS compliant. So, even though one is assured compliance with a published standard, the potential for errors related to the accuracy of the locations of landscape features can still be significant.

M a p s are a method used to convey ideas about the can be used to develop an effective map, such as leg- spatial location of resources and, when well devel- ends, scale bars, and types of maps. The representation oped, are an effective way of communicating ideas. of these components on a map may be important to cus- This chapter presented a variety of components that tomers of the map. For example, certain components

78 PART I Introduction to Geographic Information Systems, Spatial Databases, and Map Design I CHAPTER 4 Map Design

79

numbers range from 1 to 36 in almost all PLSS states, although one might find an occasional section numbered 37 where measurement irregularities warranted adjustments to the PLSS. Some states, including Oregon, Florida, and New Mexico, had adopted less rigorous land measurement systems that superceded the PLSS. Through these systems, settlers could stake

1 : 1,200 claims to lands, and these systems were generally re- 5 3 33

ferred to as DLCs. DLC boundaries are numbered 1.2,400 2 6 67

starting with 37. 1:4,800 513 33

In general, green shading (gray in the black-and- 1 : 10,000 227.78

white image of figure 4.25) is used to represent for- 1.12,000 233 33

ested or natural areas, and no shading is used to 1 :24,000 140.00

represent developed areas. Roads, streams, and other 1.63,360 t 105 60

cultural and natural landscape features are also visible 1~100,000 2166 67

throughout the map.

National Map Accuracy Standards relation to some of the more common map scales. For According to the information illustrated in figure 4.23, the Corvallis Quadrangle, this threshold would be the Corvallis Quadrangle map complies with the Na- 40 feet, indicating that not more than 10 percent of the tional Map Accuracy Standards (NMAS). These stan- tested map points should differ from their actual loca- dards were originally developed by the U.S. Bureau of tions by more than 40 feet. Vertical accuracy standards the Budget in 1941, so that guidelines would be avail- are applied by using half the contour interval as a able for the establishment of horizontal and vertical benchmark. For vertical accuracy of the primary con- map accuracy at multiple scales. The guidelines were tour lines (20' intervals) of the Corvallis Quadrangle, also intended to help protect and inform consumers the standard indicates that 90 percent of the elevation about the quality of the map products they acquired. points checked along the contour lines should not be in The guidelines assume that organizations that claim error by more than 10 feet. adherence to NMAS guidelines are responsible for en- Typically, on USGS 7.5 Minute Quadrangles, 28 suring compliance. The NMAS was last revised in points are examined for accuracy verification, repre- 1947 (Thompson 1979). senting a very small portion of the population of map

The guidelines (figure 4.26) provide horizontal ac- points. It is also worth noting that these points are not curacy standards for map scales larger than 1:20,000 randomly selected but, rather, represent locations that and for scales at 1:20,000 or smaller. For the larger are readily visible on the photography from which the

Topography by photograrr~metr~c methods from aer~al map scales, no more than 10 percent of the points ver- map was created, such as road intersections, bridges, photographs taken 1967 Field checked 1969 ified shall be in error by 1130th of an inch, as measured and other noteworthy structures. Thus, one would ex- POIYCO~IC prolect~on. 1927 North Arnertcan datum on the map surface. For smaller scale maps, this tol- pect that the points represent the mapped areas where 10,ooo-foot grid based on Oregon coord~nate system, erance is 1150th of an inch. The Corvallis Quadrangle the photogrammetric methods used to create the map north zone 1000 meter Universal Transverse Mercator gr~d ticks, falls into the latter category. To test for NMAS com- were most reliable. It is also worth noting that 10 per- zone l o , shown ~n blue pliance, locations or elevations from map points are cent of those points could be off by any distance, and To place on the predicted North Amerlcan Datum 1983. UTM GRID AN0 1986 MAGNETIC WORTH

DECLINATION AT CENTER OF SHEET compared with their actual measurements, where loca- the resulting map would still be NMAS compliant. So,

move the projection Icnes 23 meten north and tions or elevations have been derived by highly accu- even though one is assured compliance with a pub- 96 meters east as shown by dashed corner ticks

rate ground surveys. Within these comparisons, only lished standard, the potential for errors related to the There may be private inhold~ngs within the boundaries of the Nat~onal or State resewatlons shown on thls map 10 percent of the points can be in error by more than accuracy of the locations of landscape features can still

Red tlnt ~ndlcates areas In whcch only landmark bu~ld~ngs are shown , the tolerance. Table 4.1 describes the tolerances in be significant.

Figure 4.25 Lower left-hand corner of the Corvallis Quadrangle.

in chapter 2) for Oregon. Larger numbers appear on country in a grid of townships (approximately 6-by-6- the mapped surface and describe the boundaries be- mile blocks created by the intersections of township tween sections and donation land claims (DLCs). Most and range lines) that were created from a reference of the western United States was originally divided ac- meridian, with townships further divided into sec- oped, are an effective way of communicating ideas. of these components on a map may be important to cus-

cording to the PLSS. The PLSS split regions of the tions measuring approximately 1 square mile. Section This chapter presented a variety of components that tomers of the map. For example, certain con~ponents


United States National Map Accuracy Standards

With a view to the utmost economy and expedition in producing maps which fulfill not only the broad needs for standard or principal maps, but also the reasonable particular needs of individual agencies, standards of accuracy for published maps are defined as follows: r

1. Horizontal accuracy. For maps on publication scales larger than 1:20,000, not more than 10 percent of the points tested shall be in error by more than 1130 inch, measured on the publication scale; for maps on publication scales of 1:20,000 or smaller, 1150 inch. These limits of accuracy shall apply in all cases to positions of well-defined points only. Well-defined points are those that are easily visible or re- coverable on the ground, such as the following: monuments or markers, such as bench marks, property boundary monuments; intersections of roads, railroads, etc.; comers of large buildings or structures (or center points of small buildings); etc. In general what is well defined will also be determined by what is plottable on the scale of the map within 11100 inch. Thus while the intersection of two road or property lines meeting at right angles would come within a sensible interpretation, identification of the intersection of such lines meeting at an acute angle would obviously not be practicable within 11100 inch. Similarly, features not identifiable upon the ground within close limits are not to be considered as test points within the limits quoted, even though their positions may be scaled closely upon the map. In this class would come timber lines, soil boundaries, etc.

2. Vertical accuracy, as applied to contour maps on all publication scales, shall be such that not more than 10 percent of the elevations tested shall be in error more than one-half the contour interval. In checking elevations taken from the map, the apparent vertical error may be decreased by assuming a horizontal displacement within the permissible horizontal error for a map of that scale.

3. The accuracy of any map may be tested by comparing the positions of points whose locations or elevations are shown upon it with corresponding positions as determined by surveys of a higher accuracy. Tests shall be made by the producing agency, which shall also determine which of its maps are to be tested, and the extent of such testing.

4. Published maps meeting these accuracy requirements shall note this fact on their legends, as follows: "This map complies with National Map Accuracy Standards."

5. Published maps whose errors exceed those aforestated shall omit from their legends all mention of standard accuracy.

6. When a published map is a considerable enlargement of a map drawing (manuscript) or of a published map, that fact shall be stated in the legend. For example, "This map is an enlargement of a 1:20,000- scale map drawing,"or "This map is an enlargement of a 1:24,000-scale published map."

7. To facilitate ready interchange and use of basic information for map construction among all Federal mapmaking agencies, manuscript maps and published maps, wherever economically feasible and consistent with the uses to which the map is to be put, shall conform to 16titude and longitude boundaries, being 15 minutes of latitude and longitude, or 7.5 minutes, or %314 minutes in size.

\

Issuerf IUIIE 10, 1941 U.S. BUREAU OF THE BUDGET Rn~ised Aprll 26, 1943 Revised Iurrc 17, 1947

Figure 4.26 National map accuracy standards.

of maps are required when developing maps for co- map for personal use. There is no one correct format. workers or for others internal to a natural resource One should, however, have an understanding of the op- management organization; certain components are re- tions available for map products and of the intended quired when developing maps for external clients (e.g., audience. Each map developed reflects one's profes- when submitting a harvest plan to a state agency); and sionalism as a natural resource manager. certain components are required when developing a

CHAFTER 4 Map Design 81

4.1. Age class distribution of the Daniel Pickett Forest. The manager of the Daniel Pickett Forest would like you to produce a map to illustrate the age class distribution of the forest to the president of the company. Develop a thematic map showing five age classes: 0-20 years old, 21-40,41-60, 61-80, and 80+.

4.2. Age class distribution of the Brown Tract. The manager of the Brown Tract, Becky Blaylock, needs an age class distribution map for an annual report she is developing. Produce a map showing five age classes: 0-20 years old, 21-40,41-60,61-80, and 80+.

4.3. Owl nest locations on the Daniel Pickett Forest. The wildlife biologist associated with the Daniel Pickett Forest needs a map illustrating the spotted owl (Strix occidentalis) nest locations on the forest. Produce a map illustrating the two locations.

4.4. Stream types of the Daniel Pickett Forest. The hydrologist associated with the Daniel Pickett Forest needs a map illustrating the different stream types, in order to direct a summer crew to the locations to be surveyed for fish species

Produce a map illustrating the different stream types associated with the Daniel Pickett Forest.

4.5. Potential hawest unit. The land manager of the Daniel Pickett Forest is considering a timber sale in unit number 13 on the Daniel Pickett Forest. He would like you to produce a map indicating that unit 13 is a proposed harvest area and display the road and stream systems in relation to the unit.

4.6. Brown Tract trail system. The manager of the Brown Tract, Becky Blaylock, would like you to develop a map illustrating the trail system on the Brown Tract, highlighting both the authorized and unauthorized trails. This map will be used by recreationists who visit the forest. Include as reference information on the map the road system and contour elevations.

4.7. Culvert installation dates. The road engineer associated with the Daniel Pickett Forest, Bob Packard, is in the process of developing a culvert replacement plan. He would like you to develop a map illustrating the road system, the culverts, and the culvert installation dates for the Daniel

4.8 Quadrangle challenge. Locate a USGS 7.5 Minute Quadrangle near your work or school location. a. What is the name of the

Quadrangle? b. When was the map

originally compiled? c. If the map has been

updated, when was it updated?

d. What is the OHIO code description of the map?

e. When was the topography developed?

f. How much magnetic declination exists in the map?

4.9. Disclaimers, caveats, and warranties. You work for an agency that has developed a statewide streams GIs database. At one of your regular staff meetings, the discussion shifts to this GIs database and the notion of associating a disclaimer, caveat, or warranty with the GIs database. You gather from the conversation that the group is very confused about the use of the terms disclaimer, caveat, and warranty. What guidance can you provide to help them understand the differences among the terms and how the terms might be used in relation to the streams GIs database?

and habitatconditions. - Pickett property.

Documents

60 PART I Introduction to Geographic Information Systems ...fe257.forestry.oregonstate.edu/sites/fe257/files/Chapter4.pdf60 PART I Introduction to Geographic Information Systems, Spatial