Geographic coordinate system & map projection

for those interested in GIS field

1. Geographic Coordinate System & Map Projection By- Vishal Kedia M.Tech (Remote Sensing & GIS) Maulana Azad National Institute Of Technology BHOPAL

2. Our earth…( some facts) Earth is almost a Geoid ( ie . Geophysically an equipotential surface) which is a irregular spheroid like structure. Surface of G eoid matches very much with the MSL. Mathematically earth is represented as spheroid. Spheroid is the three dimensional structure formed by the rotation of an ellipse about the minor axis. For the purpose of obtaining R.L. of any point on earth surface Geoid approximation of earth is assumed. For the purpose of obtaining geographic coordinate of earth pure spheroid or ellipsoid is assumed.

3. Vertical deflection Geoid undulation Geoid Undulation: separation between geoid & spheroid at any point on the surface of the earth.

4. What is Datum?

5. Geodetic Datum:

6. Vertical Datum:

7. Different Ellipsoid Models

8. Example Datum:

9. WGS 84 – Parameters:

10. WGS 84 – Parameters(cont.)

11. Geographic Coordinate System

12. Lattitude & Longitude

13. Lattitude & Longitude(cont.)

14. Projection ?

15. Projection(cont.)

16. Projection(cont.)

17. Projection(cont.)

18. Projection(cont.)

19. Projection(cont.)

20. Rectangular coordinate system

21. coordinate system and map projection

22. Utm coordinate system

23. Utm coordinate system(Cont.) It is the modified form of Transverse Mercator Projection System in which instead of using one cylinder as developable surface we use multiple cylinders that touch the globe at 6 degree interval meridians resulting in 60 projection zones each of 6 degree longitude width. To avoid extreme distortions projection zones are limited to 84 N & 80 S.

24. Utm coordinate system (Cont.) UTM coordinate system is formed by superimposing a regular grid on each projection zone such that vertical lines are parallel to the central meridian. Each UTM zone is divided into horizontal bands spanning 8 degrees of lattitude & these are identified by the letters North to South beginning at 80 S with letter ‘c’ and ending at 84 N with letter ‘X’ , letter ‘I’ & ‘O’ are not used (skipped). Band ‘X’ spans 12 degrees of lattitude .

25. Utm coordinate system (Cont.)

26. Utm coordinate system (Cont.) UTM coordinates are expressed as a distance in meters to east – ‘Easting’ & to north – ‘Northing’. UTM easting of central meridian is 500,000 m east ie . false origin is 500,000 m west of the central meridian.

27. Utm coordinate system (Cont.) Equator is assigned 0 m N (zero northing). To avoid – ve nos for locations south of the equator position fixing in the southern hemisphere is made with equator assigned a value of 10,000,000 m S. By combining the zone no, the hemisphere, easting and northing values; each point on the earth surface can be uniquely located.

28. Any questions?

29. Thanking you!