Geographical Reference Systems (WIP)

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Latitude and Longitude

UTM

UTM Zones

UTM divides the Earth into 60 zones stretching from 180°W to 180°E and each zone is 6° in width. (Zone 01 covers longitude 180°W to 174°W and zone 60 covers longitude 174°E to 180°E). The zone number are followed by N or S to indicate northern or southern hemisphere. (Eg 33N)

UTM refers to an exact position and are given as the distance in meters relative to the each zones central meridian and the equator.
The central meridian coincide with 500000mE and are the thin blue lines presented in the image on the right. Any position along those lines have an easting value of about 500000mE.

The red dot in the image on the right indicates the city of Motala which has a position of 33N 502741mE 6488614mN.

MGRS

MGRS is based on the zones in UTM but also devides the Earth into 20 bands (C-X, omitting the letters "I" and "O") stretching from 80°S to 84°N and each band is 8° (Band X is 12°) in hight. (Band C covers latitude 80°S - 72°S and X covers latitude 72°N - 84°N)

Each UTM Zone is devided into 10 mile squares. The squares are named with two letters, the first is a column letter (A–Z, omitting "I" and "O") followed by a row letter (A–V, omitting "I" and "O").

Finally, the position is indicated within the 10 mile square measured from the bottom left. The position can be given in 2-10 digits (always even) depending on the resolution and they are equaly devided in two sets (Eg 2+2, 4+4 etc.). The first set gives the easting measured from the left edge of the square and the second set gives the northing measured from the bottom edge. The first digit in each set is the amount of miles, 2nd=kilometers, 3d=hundreds of meters, 4th=tens of meters and 5th=meters. (eg. a 10 digit position defines a square 1m x 1m) Note that the precision of the coordinate depends on what system you use and how you use it. The TGP might give you a 10 digit grid, but if you don't use the LRF when measureing, it won't be as accurate. (You will just miss the target more precisce)

Exampel: KUTAISI Towers position in 10 digit MGRS.