Speaker Shagufta Akbari

Assistant Prof.KL University

Introduction Map as a model Spatial elements and terminology Classification of Maps Map Scale Spatial referencing system Computers in map production General software’s in map production Types of data products

Image interpretation strategy Levels of interpretation keys Topography Types of Drainage pattern and Texture Erosion Process of image interpretation Basic elements of image interpretation Overview on visual image interpretation

equipment

Map as Model◦ Representation of features of earth drawn to scale◦ “A map is a very powerful tool and maps are

typical reductions which are smaller than the areas they portray” (Robinson et.al 1984)

Spatial objects in the real world can be thought of as occurring in four easily identifiable types namely, points, lines, areas and surfaces

Points, lines and areas can be represented by using symbols to depict the real world.

Surfaces are represented by any combination of these spatial entities.

In general, all the geographic surfaces are in two tangible forms, namely, discrete and continuous.

Trees, houses, road intersections and similar items are

discrete spatial features.

On the basis of scale◦ Small scale map◦ Large scale map- urban plan map, transportation

and network map

The ratio between the reduced depiction on the map and the geographical features in the real world is known as the Map Scale

Scale expressed in three ways: Fractional scale Graphical Scale Verbal Scale

◦ Fractional scale -the method of representing this type of scale is called representation fraction method

◦ In India commonly used fractional map scales are 1:1,00,000,00; 1:250,000, 1:50,000; 1:25,000 and 1:10,000

Graphical Scale- A line printed on the map and divided into units that are equivalent to some distance

The measured ground distance appears directly on the map in graphical representation

Verbal Scale- This is an expression in common speech like “an inch to a mile”

To locate objects with respect to some reference system

Methods of spatial referencing systems◦ Geographic coordinate systems-

Denoted by latitude and longitude

◦ Rectangular coordinate systems(RCS) Spatial data are in two-dimensional form Relative position- location of any point on the earth’s

surface w.r.t RCS

◦ Non- coordinate systems Spatial reference with descriptive codes such as postal

codes which is non-numeric in nature

Advantages To make existing maps more at a quicker pace

To make existing maps at a cheaper rate

To make maps for specific user needs

To make map production possible in situations where skilled staff are unavailable

To allow experimentation with different graphical representations of the same data

To facilitate map making and updating when the data are already in digital form

To minimize the use of the printed map as a data store and thereby to minimize the effects of classification and generalization on the quality of the data

Introduction of automation can lead to a review of the whole map – making process , which can also lead to savings and improvements

Arc- GIS ARC- VIEW etc.

Figure . Digitizing tablet (left) and a Wide-format scanner (right)

Figure . Typical map production workflow.

Data compilation involves gathering and collecting any spatial and/or attribute data that you will need for creating your map.

In some cases, the data that you will need for the particular map you want to create will already exist in a digital format that can be directly imported into a GIS.

Your own organization may have already collected the data, or they may have been created by a government agency, non-profit organization or private firm.

In other cases, the data you would like to use may exist, but are in an analog rather than digital format. In this situation, you can often use a digitizing tablet or a scanner to transform the data into a format that a GIS can use.

Although an immense amount of digital geospatial data already exists, you may still find yourself in the position of having to create your own data, either because no one has already collected it or because the available data is not suitable for your purposes (e.g. a civil engineering firm will most likely need more precise elevation data for planning road grades than what they can extract from a 30 meter resolution DEM).

In this case, you may need to use surveying equipment or a GPS receiver

The second step in the map production workflow is the actual designing of the map.

Most computer-assisted map production used to be done with graphics illustration software.

However, the cartographic tools in GIS software packages have gradually been improving.

It is now possible (in at least some software packages) to create all of the components needed for offset printing within the GIS software.

Some examples of GIS software packages you might use for map production include: ArcGIS, MapInfo, IDRISI, Intergraph Geomedia, and Autodesk Map.

Although the cartographic tools embedded within GIS software have been improving, you may find that there are some operations that you either just cannot perform in the GIS, or that are tedious and cumbersome in this software environment.

Often, cartographers turn to graphic design software for more sophisticated functionality and more precise control over graphic elements.

Graphic design software falls into three major categories: illustration

software, image-editing software, and page-layout software.

Illustration software is vector based (i.e. the file contains objects such as points, lines and polygons that you can manipulate )

Some of the more popular packages include Adobe Illustrator, Macromedia Freehand, and CorelDRAW. ◦ Image-editing software, on the other hand, is raster based (i.e. it is

pixel-based rather than object based).

Cartographers often use image-editors such as Adobe Photoshop, Corel Painter, or Paintshop Pro to further enhance shaded relief in their maps.

Page-layout software—such as QuarkXPress, Corel Ventura, and Adobe InDesign (formerly known as PageMaker)—combines both the vector and raster graphics handling capabilities of illustration and image-editing software packages

Types of data productsDepending on correction applied & level of processing

Note: FCC are generated by combininig the data contained in three spectral bands respectively. The choice of band combinations can be determined depending upon application

Image interpretation strategyVisual image interpretation : Process of

indentifying what we see on the images and communicate the information obtained from these images to others for evaluating its significance

Includes relative locations and extents

Use of data products like Satellite single band imageries, FCC for performing image interpretations to extract thematic information for subsequent input to GIS

Interpretation Keys: Criterion for identification of an object with interpretation elements

Size of objects in an image is a function of scale

Proper photo scale selected depending on the purpose of interpretation

Most commonly measured parameters:- length, width, perimeter, area and occasionally volume

Size of an objects on images must be considered in the image scale.

Relative sizes among objects on images of the same scale must be considered

Shape of an object is described as the geometric form represented form represented on an image

Regular shapes are signs of man-made objects

Irregular shapes with no distinct geometrical pattern are signs of a natural environment

Refers to the general form, configuration , or outline of individual objects.

All shapes are not diagnostic, but every shape is of some significance to the image interpreter

The shape of some objects are so distinctive that their images may be indentified by shape

The pentagon building near Washington DC is a classic example

Patten relates to the spatial arrangement of objects

Repetition of certain general forms or relationships is characteristic of many objects, both natural or constructed, and gives objects, both natural and constructed, and gives objects a pattern that aids the image interpreter in recognizing them

Eg. ordered spatial arrangement of trees in an orchard is in distinct contrast to that of forest tree stands

Shadow – usually a visual obstacle for image interpretation

Gives height information about towers, tall buildings

Hobject

SShadow

tan HS

Band of EM spectrum recorded by RS system may be displayed in shades of grey ranging from black to white

Tone:- ◦ continuous grey scale varying from white to black◦ It refers to relative brightness or colour of objects

in an image

Note:- Humans differentiate 40- 50 individual shades of grey RS image

Colour ◦ more convenient for the identification of object

details

Texture◦ Characteristics placement & arrangement of

repetitions of tone or colour in an image◦ Visual impression of roughness or smoothness of

an image region