Remote Sensing and Image Interpretation

1. Remote Sensing and Image Interpretation Speaker Shagufta Akbari Assistant Prof. KL University

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 …… • 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

12. General software’s in map production • Arc- GIS • ARC- VIEW etc.

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

16. Basic elements of image interpretation

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

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