Concept of Geographic coordinate systems and map projections

1. Concept of Geographic coordinate systems and map projections

2. Objectives • Understand the concept of coordination system • Understand the map projections Why it is important?

3. Y (+X,+Y) (-X,+Y) X (-X,-Y) (+X,-Y)

4. Y X X - Equator. Y - Prime Meridian Lat/Long are the coordinate of point on earth.

6. N (N, W) (N, E) E W (S, W) S (S, E)

7. What are the latitude and longitude directions of Kazakhstan?

8. Latitude and Longitude Latitude - distance from the equator along the Y axis Longitude - distance from the prime meridian along the X axis. .

9. Exercise In Which Quarter These Lon/Lats Are Located • 43 °N, 21°E • 78°S, 111°W • 4°S, 23°E • 15°N, 29°E

10. Coordination systems

11. Other coordinate systems If two datasets are not referenced to the same geographic coordinate system, you may need to perform a geographic (datum) transformation. This is a well-defined mathematical method to convert coordinates between two geographic coordinate systems. As with the coordinate systems, there are several hundred predefined geographic transformations that you can access.

12. East is the direction of rotation of the Earth Latitude: (90oN to 90oS) Longitude: (180oE to 180oW) Prime Meridian 0o Longitude Tropic of Cancer Latitude 23½o North 21st June 66½o 90oE 60oE 30oW 30oE 60oW 90oW 23½o 90o 22nd Sept 20th March North Pole Equator Latitude 0o 23½o 900 22nd December Tropic of Capricorn Latitude 23½o South Longitude 90o West Longitude 90oEast Longitude 60o West Longitude 60o East Longitude 30o West Longitude 30o East South Pole Positioning on the Earth’s Surface Geographical coordination system Latitude and Longitude together enable the fixing of position on the Earth’s surface.

13. Map Projection • 3D surface is transformed to create a flat surface • This transformation, usually by a mathematical conversion, is commonly referred to as map projection • A 2D surface is imagined around the Earth and is referred as projection surface

14. Which projection is the best

15. Projection for accurate mapping • Earth is neither a perfect sphere nor a spheroid • Local irregularities • Earth surveyed many times to determine semi-minor and semi-major axis • Semi-minor and semi-major axis that fits well one region may not fit well another region

16. Type of Projection • Projection surfaces • Conic, cylindrical, and planar • ARC/INFO supports 46 projections

17. ARC / INFO supports • 26 spheroids • Each region is represented by a unique semi-minor and semi-major axis • Measurements vary but by a little amount relative to the magnitude of the Earth

19. Conic Projection • The most simple conic projection is tangent to the globe along a line of latitude • This is called a standard parallel for a projection • The meridians are projected onto the conical surface, meeting at the apex • latitudes are projected as rings onto the conical surface

21. Cylindrical projections Cylindrical projections may also have one line of tangency or two lines of secancy around the globe. Mercator projection is one of the most common cylindrical projections, and the Equator is usually its line of tangency. Meridians are Geometrically projected onto the cylindrical surface, and latitude parallels are mathematically projected, producing graticular angles of 90 degrees.   For more complex cylindrical projections the cylinder is rotated thus changing the lines used for tangency or secancy.

22. The cylinder can be 'cut' along, any meridian to produce the final cylindrical projection. The meridians are equally spaced, while the spacing between parallel lines of latitudes increases toward the poles. This projection is conformal and display true direction along straight lines.

23. Transverse Mercator uses meridians as their tangential contact line. Oblique Cylinders are rotated around a great circle line located anywhere between the Equator and the meridians. In these complex projections most meridians and the lines of latitudes are not straight. In all cylindrical projections, the line of tangency or lines of secancy have no distortion and thus are lines of equidistance. Other geographical properties vary depending on the specific projection.

32. Assignment Explain in 2 pages which map projection are you using and compare with another projection which you are not using Literature for reading • http://en.wikipedia.org/wiki/Geographic_coordinate_system ^ a b c d e f A Guide to coordinate systems in Great Britain v1.7 October 2007 D00659 accessed 14.4.2008 ^ The International Meridian Conference ^ Haswell, Charles Haynes (1920). Mechanics' and Engineers' Pocket-book of Tables, Rules, and Formulas. Harper & Brothers. Retrieved 2007-04-09. ^ University of New South Wales Instrument Collection Wild T4 ^ The NGS [1] gives the NAD83 co-ordinates of the water tank; [2] estimates the vertical deflection, the difference between NAD83 and lat-lon by the stars. ^ Minor light of Hawai'i - Keahole Point, HI LightHouse Friends ^ NGS [3] gives the NAD83 co-ordinates and [4] again converts to astro lat-lon. ^ http://www.ngs.noaa.gov/cgi-bin/ds_mark.prl?PidBox=tu1252