MGRS NGA Information (concerning map scale, etc)



2-6.1 Military grids consist of parallel lines intersecting at right angles and forming a regular series of squares. The north-south lines are called eastings and the east-west lines northings. Each grid line is one of an even-interval selection of measurement units. The interval is selected in accordance with the map scale. The unit intervals shown on military map scales are:

1:12,500 1,000
1:25,000 1,000
1:50,000 1,000
1:100,000 1,000 or 10,000
1:250,000 10,000
1:500,000 10,000
100,000 with ticks at 10,000

Table 4. Grid Unit Intervals for Various Scale Topographic Maps.

2-6.2 The grids preferred for military maps are:

2-6.2.1 Universal Transverse Mercator (UTM) grid for areas between 80° south and 84° north.

2-6.2.2 Universal Polar Stereographic (UPS) grid for the polar regions south of 80° south and north of 84° north. 2-6.2.3 Other grids for certain parts of the world as shown in Appendix D. These grids are being progressively replaced by the UTM grid, with the intent to eventually cover all military mapping of the world with a universal metric grid system.

2-6.2.4 Area of application for the various other grids are given in Appendix D. A general description of the grids and numbering systems is given in Chapter 4.

2-6.3 Specifications for the Universal Grid Systems follow:

2-6.3.1 Universal Transverse Mercator (UTM) Grid.

Projection: Transverse Mercator (Gauss-Kruger type) in zones 6° wide.

Ellipsoid: International Bessel 1841 World Geodetic System 1984 Geodetic Reference System (GRS 1980)

Longitude of Origin: Central meridian (CM) of each projection zone (3°, 9°, 15°, 21°, 27°, 33°, 39°, 45°, 51°, 57°, 63°, 69°, 75°, 81°, 87°, 93°, 99°, 105°, 111°, 117°, 123°, 129°, 135°, 141°, 147°, 153°, 159°, 165°, 171°, 177°, E and W).

Latitude of Origin: O° (the Equator).

Unit: Meter.

False Northing: 0 meters at the Equator for the Northern Hemisphere; 10,000,000 meters at the Equator for the Southern Hemisphere.

False Easting: 500,000 meters at the CM of each zone.

Scale Factor at the Central Meridian: 0.9996.

Grid Zone Designations: See Chapter 3 and Appendix B.

Latitude Limits of System: From 80°S to 84°N.

Limits of Projection Zones: The zones are bounded by meridians, the longitudes of which are multiples of 6° east and west of the prime meridian.

Overlap: On large-scale maps and trig lists, the data for each zone, datum, or ellipsoid overlaps the adjacent zone, datum, or ellipsoid a minimum of 40 kilometers. The UTM grid extends to 80°30’S and 84°30’N, providing a 30-minute overlap with the UPS grid.

2-6.3.2 Universal Polar Stereographic (UPS) Grid.

Projection: Polar Stereographic.

Ellipsoid: World Geodetic System 1984

Longitude of Origin: O° and 180°E-W.

Latitude of Origin: 90°N and 90°S.

Unit: Meter.

False Northing: 2,000,000 meters.

False Easting: 2,000,000 meters.

Scale Factor at the Origin: 0.994.

Grid Zone Designations: See Chapter 3 and Appendix B.

Limits of System: North Zone: Polar area north of 84°N. South Zone: Polar area south of 8O°S.

Overlap: The UPS grid extends to 83°30’N and 79°30’S, providing a 30-minute overlap with the UTM grid.

2-6.4 Formulas for constructing UTM and UPS grids are contained in DMA TM 8358.2.


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