Lesson1 NEW

8/2/2019 Lesson1 NEW

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Introduction to ArcGIS Introduction to GIS

Definitions of a geographic information system can vary considerably. The definition provided here

combines both the components and functions of a GIS. The components needed to perform GIS

tasks include:

People

This is the most important component in a GIS. People must develop the procedures and define the

tasks of the GIS. People can often overcome shortcomings in other components of the GIS, but the

best software and computers in the world cannot compensate for the incompetence of people.

DataThe availability and accuracy of data can affect the results of any query or analysis.

Hardware

Hardware capabilities affect processing speed, ease of use, and the type of output available.

Software

This includes not only actual GIS software but also various databases, drawing, statistical, imaging,

or other software.

Procedures

Analysis requires well-defined, consistent methods to produce accurate, reproducible results.

A geographic information system (GIS) is a collection of hardware, software, geographic

data, and personnel designed to create, store, edit, manipulate, analyze and display

geographically referenced information.


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GIS functions

Any GIS should be capable of the following fundamental operations in order to be useful for findingsolutions to real-world problems.

Capturing data

A GIS must provide methods for inputting geographic (coordinate) and tabular (attribute) data. The

more input methods available, the more versatile the GIS.

Storing data

There are two basic data models for geographic data storage: vector and raster. A GIS should be

able to store geographic data in both models.

Querying data

A GIS must provide utilities for finding specific features based on location or attribute value.

Analyzing data

A GIS must be able to answer questions regarding the interaction of spatial relationships between

multiple datasets.

Displaying data

A GIS must have tools for visualizing geographic features using a variety of symbology.

OutputA GIS must be able to display results in a variety of formats, such as maps, reports, and graphs.


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Capturing data

Because the geographic database is the expensive and long-lived component of the GIS, data entry

is an important consideration. ArcGIS integrates a variety of data types from a variety of sources, so

it provides multiple data entry options. ArcGIS offers efficient data entry methods for automating

paper maps and other non-digital data sources. To take advantage of the vast collection of

geographically referenced data that already exists in digital format, ArcGIS provides the most

comprehensive data conversion capability of any GIS on the market. ArcGIS softwares integrative

capabilities also allow data to be shared with other applications without the need for conversion.


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Storing data

You can represent geographic features in vector or raster format.

Vector data

In a vector data structure, geographic features (such as wells, roads, national parks, etc.) are

represented by points, lines, and polygons that are defined by a set or sets of [X,Y] coordinates.

Raster data

Instead of representing features by their x, y coordinates, the raster data model assigns values to

cells that cover coordinate locations. Raster format is well-suited to spatial analysis and is also

appropriate for storing data collected in grid format. The amount of detail you can show for a

particular feature depends on the size of the cells in the grid. This makes raster data inappropriate

for applications where discrete boundaries must be known, such as parcel management.


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Query

Identifying specific features

One common type of GIS query is to determine what exists at a particular location. In this type of

query, the user understands where the features of interest are but wants to know what

characteristics are associated with them. This can be accomplished with GIS because the spatial

features are linked to the descriptive characteristics.

Identifying features based on conditions

Another type of GIS query is to determine the locations that satisfy certain conditions. In this case,

the user knows what characteristics are important and wants to find out where the features are that

have those characteristics.


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Analysis

You can perform analysis to obtain the answers to a particular question or find solutions to a

particular problem. Geographic analysis usually involves more than one geographic dataset and

requires the analyst to proceed through a series of steps to reach a result. Three common types of

geographic analysis are:

Proximity analysis

How many houses lie within 100 meters of this water main?

What is the total number of customers within 10 kilometers of this store?

What proportion of the alfalfa crop is within 500 meters of the well?

To answer such questions, GIS technology uses a process called buffering to determine the

proximity between features.

Overlay analysis

An overlay process combines the features of two layers to create a new layer that contains the

attributes of both. This resulting layer can be analyzed to determine which features overlap or to

find out how much of a feature is in one or more areas. An overlay could be done to combine soil

and vegetation layers to calculate the area of a certain vegetation type on a specific type of soil.

Network analysisThis type of analysis examines how linear features are connected and how easily resources can

flow through them.


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Display

For many types of geographic operations, the end result is usually best visualized as a map or

graph. Maps are efficient for storing and communicating geographic information. Cartographers

have created maps for millennia, but GIS provides new and exciting tools to extend the art and

science of cartography. Maps can be integrated with reports, three-dimensional (3D) views,

photographic images, and other digital media.

Output

Sharing the results of your geographic labour is one of the primary justifications for investing

resources in GIS. A powerful method for sharing displays created through a GIS is to output them

into a distributable format. The more output options a GIS can offer, the greater the potential for

reaching the right audience with the right information.


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Organizing spatial data

A GIS organizes and stores information about the world as a collection of thematic layers that can

be linked by geography. Each layer contains features with similar attributes, like streets and cities

that are located in the same geographic extent. This simple, but powerful and versatile, concept has

proven invaluable for solving real-world problems from tracking delivery vehicles to modeling global

atmospheric circulation.

The onion analogy

Think of the world as a large onion. When you peel an onion, you see that it is composed of many

layers. Real-world entities can be seen the same way; the earth can be peeled into many layers,

each representing a different theme. For example, you can put all the streets in one layer and all the

landuse areas in another layer. As you can imagine, the earths complexity allows you to create as

many layers as you want. The question then becomes how to best organize these real-world

entities into manageable geometric shapes (point, line, area) and store them digitally.


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Representing features in vector data

Real-world entities are abstracted into three basic shapes

Abstracting real-world entities

It is impossible to capture everything from reality inside a computer. Instead, GIS users must

somehow abstract real-world phenomena, or entities, into a geometric representation of those

entities. There are three basic geometric shapes used for geographic features: points, lines, and

areas. These shapes can be called geometric objects, geometric features, or feature types. Note

that there are different methods of making these entities digital, including scanning and digitizing.

Point A single location having an X, Y (and sometimes, a Z) position (point features haveno area and no length)

Line / Arc A series of connecting X, Y positions (line features have length, but no area)Polygon One or more connecting lines that form a single spatial feature (polygon features

have both area and perimeter)Vertex One of a set of ordered X, Y coordinate pairs that define a line or polygon feature.

More simply, a location along a line where the line changes direction giving it shape(similar to a point)


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Map scale

Map scale is an important but often misunderstood concept in cartography. To represent a portion

of the earths surface on a map, the area must be reduced. The extent of this reduction isexpressed as a ratio called map scale. Map scale is the ratio of map distance to ground distance.

For example, if you draw a 4.8-km road as a 20-cm line on your map, the following statements

would describe the map scale:

20 cm:4.8 km, 20 cm:480,000 cm, 1 cm:24,000 cm, 1:24,000

The latter is known as a representative fraction (RF) because the values on either side of the colon

represent the proportion between distance on the map and distance on the ground; that is,

1:24,000 means 1 map inch represents 24,000 ground inches, 1 map meter represents 24,000

ground meters, or 1 map centimeter represents 24,000 ground centimeters, and so on.

Map scale can be expressed in several different manners: as a fraction (1:24,000), as a verbal

statement (one centimeter equals one kilometer), or as a bar. Map scale indicates how much a

given distance was reduced to be represented on a map. For maps with the same paper size,

features on a small-scale map (1:1,000,000) look smaller than those of a large-scale map (1:1,200).

In other words, a dime-sized lake on a large scale map (1:1,200) would be less than the size of the

period at the end of this sentence on a small-scale map (1:1,000,000).

In general, small-scale maps depict large ground areas, but they have low spatial resolution,

showing little detail. On the other hand, large-scale maps depict small ground areas but have high

spatial resolution, showing many details. The features on large-scale maps more closely representreal-world features because the extent of reduction is lower than that of a small-scale map. As map

scale decreases, features must be smoothed and simplified or not shown at all. For example, at a

scale of 1:63,360 (in which 1 inch = 1 mile), it is difficult to represent area features smaller than

1/8th of a mile long or wide because they will be 1/8th of an inch long or wide on a map.


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Components of geographic data

GeometryGeometry represents the geographic features associated with real-world locations. Geographic

features are abstracted into points, lines, or areas.

Attributes

Attributes provide descriptive characteristics of the geographic features.

Behavior

Behavior means geographic features can be made to follow certain types of editing, display, or

analysis rules, depending on circumstances defined by the user.


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Using spatial relationships

The relative position of features determines relationships

The relationships between features on a map, or where they are located in space relative to one

another, communicate important information. Connectivity, adjacency, and containment are types ofspatial relationships shown in the graphic above. Interstate 80 connects San Francisco with New

York City. San Francisco is adjacent to the Pacific Ocean, and California is within the USA.

Features may also have coincidence; for example, California and Nevada are both separate

polygons, yet each has a common boundary line in the exact same space as the other, these lines

are seen to be coincident.

The spatial relationships between connecting, coincident, or adjacent features in a geographic data

layer are often referred to as topologic relationships. Topology is the branch of geometry that deals

with the properties of features that remain unchanged even when the features are bent, stretched,

or otherwise distorted. ArcGIS uses these spatial relationships and feature properties like area,

length, and direction to identify complex spatial patterns.

Coordinate Systems

Spatial data are data that are georeferenced. That is, they are referenced to the surface of the

earth using either a geographiccoordinate system or a Cartesian (projected) coordinate system.

Geographic coordinate systems use latitude and longitude for coordinates. Even though only two

coordinates are required to locate a point on the earths surface, latitude/longitude are three-

dimensional coordinates because the earths surface is three-dimensional. Projected coordinate

systems use a mathematical conversion to transform latitude and longitude coordinates that fall onthe earths three-dimensional surface to a flat two-dimensional surface. A projected coordinate

system is made up of a spheroid, datum, projection, and horizontal units (i.e. map units).

ArcGIS can work with data stored in either geographic or projected coordinates.


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Spatial Data Types Supported by ArcGIS

The following data file types (i.e., data structures) are compatible with ArcGIS software. This is

important information when you are requesting data from others.

Vector Data

ArcInfoCoverage

Topological layer, actually a collection of files in a directory that are linked toadditional files found in the INFO directory. The INFO directory lives at the samelevel as the coverage directory.

ArcViewShapefile

Non-topological layer, made up of at least three (and sometimes more) files withthe following extensions, .shp, .shx, and .dbf

ArcGISGeodatabase

A collection of feature datasets and classes - point, line, polygon - with topology(*.mdb extension)

CADDdatasets

MicroStation design files (.dgn)AutoCAD drawing files (.dwg) and drawing interchange files (.dxf)

Raster DataImages DOQQs, DRGs, with file extensions such as .tif, .bil, .jpg, .sid, etc.ArcInfo Grid A raster data file analogous to an ArcInfo coverage, e.g., DEMs.

Tabular Data

Comma or tab delimited text (.txt) or dBase (.dbf) files containing coordinate data (X, Y coordinates).

Metadata

Metadata, often referred to as data about data, describes the content, quality, condition and

other characteristics of a geospatial dataset. The Federal Geographic Data Committee (FGDC)

has adopted a content standard for metadata that all federal agencies are required to use to

document newly created geospatial data. The FGDC content standard is a set of terms and

definitions for documenting geospatial data and includes data elements organized under the

following topics:

IdentificationInformation

Basic information about the data set such as title, geographic area covered, datedeveloped, stipulations regarding use of the data, etc.

Data QualityInformation

Information about the quality of the data such as positional and attribute accuracy,data sources, methods used to produce the data, etc.

Spatial DataOrganizationInformation

Information about the method used to represent spatial features in the dataset(e.g., raster, vector, street addresses, county codes, etc.).

Spatial

ReferenceInformation

Description of the reference frame for and method of encoding coordinate data

including name of map projection or grid coordinate system, horizontal andvertical datums, and coordinate system resolution.Entity andAttributeInformation

Names and definitions of features, attributes, and attribute values contained in thedataset.

DistributionInformation

Information about obtaining the dataset including name of distributor, availabledata format(s) and media, online availability, and fees.

MetadataReferenceInformation

Information on who prepared metadata and when.


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ArcGIS Desktop Products

Tools and database functionalities vary between ArcGIS products

The ArcGIS Desktop includes a suite of integrated applications: ArcMap, ArcCatalog, and

ArcToolbox interfaces. Using these applications together, you can perform any GIS task, simple toadvanced, including mapping, data management, geographic analysis, data editing, and

geoprocessing. In addition, ArcGIS allows you to tap in to an abundance of spatial data and

resources available through ArcIMS services on the Internet or stored in an ArcSDE database. The

ArcGIS Desktop is a comprehensive, integrated, scalable system designed to meet the needs of a

wide range of GIS users.

The ArcGIS Desktop can be accessed using three software products, each providing a higher level

of functionality. ArcView provides comprehensive mapping and analysis tools along with simple

editing and geoprocessing tools. ArcEditor includes the full functionality of ArcView, plus advanced

editing capabilities. ArcInfo extends the functionality of both to include advanced geoprocessing and

also includes the applications for ArcInfo Workstation (Arc, ARCPLOT, ARCEDIT, and so on).

The current release of ArcGIS is version 9.x. Versions of ArcGIS are not backward compatible,

meaning that map documents created in version 9.x can NOT be used with earlier versions (e.g.,


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version 8.x). However, this limitation is expected to be removed in version 9.1. As with most

software, the versions ARE forward compatible. Map documents that you create in an earlier

version (say 8.x) can be opened and manipulated in version 9.x.

Because the ArcGIS products all share a common architecture, users working with any of these

clients can share their work with other users. Maps, data, symbology, map layers, custom tools and

interfaces, reports, metadata, and so on, can be accessed interchangeably in all three products.

Much more information about the entire ESRI product line can be found at http://www.esri.com.

Overview of applications

All ArcGIS products share common applications

ArcMap, ArcCatalog

ArcToolbox and Command Line windows

All ArcGIS products (ArcView, ArcEditor, and ArcInfo) are comprised of the ArcMap and ArcCatalog

applications, both of which contain the Toolbox and Geoprocessing windows. ArcMap is the

application for performing analysis and making maps. ArcCatalog is a tool for accessing and

managing your data. ArcToolbox contains tools for data conversion and management. The

Geoprocessing window allows you to write, import and run scripts, and access individual

commands.


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ArcMap

Primary display application

Perform map-based tasks

Displaying

Editing

Querying

Analyzing

Charting

Reporting

ArcMap provides tools for creating visual displays of your data, querying, and creating presentation-

quality maps. ArcMap makes it easy to lay out your maps for printing, embedding in other

documents, or electronic publishing. It also includes analysis, charting, reporting functions, and a

comprehensive suite of editing tools for creating and editing geographic data. When you save a

map, all of your layout work, symbols, text, and graphics are automatically preserved.

ArcMap is the primary ArcGIS application for displaying, querying, editing, creating, and analyzing

data.

ArcCatalog

A window into your database

Browse your data

Manage your data

Create and view data

documentation (metadata)


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ArcCatalog is the data management application of ArcGIS. The ArcCatalog application helps you

organize and manage all your GIS data. ArcCatalog allows you to import, export, and preview

datasets, drag and drop data to open ArcMap, and create feature class datasets and

geodatabases. The Metadata function of ArcCatalog allows you to view, create, and/or edit

metadata.

Because spatial data may be composed of complicated file structures or multiple related files, it is

important to use ArcCatalog rather than Windows Explorer to manage your data. With ArcCatalog,

these complicated relationships are simplified and you can move, copy, or delete all related files

with one operation rather than many.

ArcToolbox Window

Available in ArcCatalog and ArcMap

Geographic processing functions Data management, analysis, and conversion

Tools vary between ArcGIS products

ArcToolbox was a separate application in ArcGIS 8.x, but is now a component of ArcCatalog and

ArcMap. The ArcToolbox window provides you with tools for data conversion, managing coordinate

systems, changing map projections, and more. ArcToolbox supports easy-to-use drag-and-drop

operations from ArcCatalog; with ArcMap, you need to browse to or type in the variables. For

ArcInfo users, ArcToolbox provides additional and more sophisticated data conversion and spatial

analysis tools.


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Getting help

Tabs

Contents

Index

Search

Favorites

Other help

Whats this?

Tool tips

Online Support

The ArcGIS Desktop Help provides several methods for finding the help you need to use the

software most productively. The Contents tab lets you search for information by topic. The Index tab

lets you search for topics containing words from the Help index, such as Layer or Table. The Search

tab lets you search the Help document for a word you specify. The Favoritestab lets you store your

favorite help topics so you can easily access them when needed. Your word does not have to be in

the index in order to search the document for it, but the search will take longer if it is not in the

index.

In ArcCatalog, ArcMap, and ArcToolbox, button and tool names are displayed when you move the

mouse over them (these are called ToolTips). You can also click the Whats This?tool in ArcMap or

ArcCatalog and then click on a button or tool to access additional help about it (this is called

context-sensitive help). For applications like ArcMap that have graphical user interfaces, context-

sensitive help is useful for finding out what all the various buttons and tools do.

Selecting the ESRI Support Center link will connect you with a wealth of additional online resources.

The Web site URL is http://support.esri.com.


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ArcGIS Extensions

Different users will have different requirements and expectations from the software. ESRI offers

several specialized tools called extensions that cater to many specialized fields. Extensions are

optional software modules that add specialized tools and functionality to ArcGIS Desktop. Note that

these extra modules need to be purchased separately.

Documents

Lesson1 NEW