2. contents
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
3. Continued ……Continued ……
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
4. 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)
5. Spatial elements and terminology
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.
6. Classification of Maps
On the basis of scale
Small scale map
Large scale map- urban plan map, transportation and
network map
7. Map Scale
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-the method of representing this type of
scale is called representation fraction method
8. 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”
9. Spatial referencing system
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
numeric in nature
10. Computers in map production
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
11. Continued…
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
13. Types of data products
Depending 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
14. Image interpretation strategy
Visual 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
15. Levels of interpretation keys
Interpretation Keys: Criterion for identification of an
object with interpretation elements
17. Size
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
18. Shape
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
19. Shadow
Shadow – usually a visual obstacle for image
interpretation
Gives height information about towers, tall buildings
H
object
S
Shadow
θ
tan
H
S
θ =
20. Tone
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
21. 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
To create maps in which selection and generalization procedures are explicitly defined and consistently executed
Geocoded products:data: systematically & geometrically corrected products :data: products are north oriented and compatible to survey of India mapsheet
It means overlays of this data with survey of india map can be performed
Regular shapes are signs of man-made objects- buildings, roads and cultivated fields
Irregular shapes with no distinct geometrical pattern are signs of a natural environment- water body or a river
For eg. In panchromatic photograph Dry sand appears white, while wet sand appears black
