Universal Transverse Mercator (UTM), the Military Grid Reference System (MGRS), and the Universal Polar Stereographic (UPS)
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OVERVIEW---- UTM coordinates are based on a family of 120 Transverse Mercator map projections (two for each UTM zone, with one for each N/S hemisphere). The earth is divided into 60 zones, each 6° wide in longitude (with the exception of a few non-standard-width zones for Svalbard and southwest of Norway). See (Figure 1).
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Figure 1. 60 UTM Zones divided North and South. Top↑
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DESIGN---- UTM divides the earth into 60 zones, each 6° wide in longitude (with the exception of a few non-standard-width zones for Svalbard and southwest Norway).
- UTM is limited to the area between 84°N and 80°S. Beyond that, Universal Polar Stereographic (UPS) coordinates are used. See section on UPS.
- The X value, called the Easting, has a value of 500,000m at the central meridian of each zone. See (Figure 2).
- The Y value, called the Northing, has a value of 0m at the equator for the northern hemisphere and 10,000,000m at the equator for the southern hemisphere. See (Figure 3).
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Figure 2. Easting Values. Top↑
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Figure 3. Northing Values. Top↑
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POSITIONING IN UTM---- Read below to know how to reference or express a position in Universal Transverse Mercator (UTM) coordinates. See (Figure 4).
- In the UTM system, positions are expressed as Easting / Northing, e.g. 580817mE, 4251205mN. In some cases, the letters are left off, e.g. 580817 4251205.
- If positions occur near UTM zone junctions, the UTM zone may also be specified, e.g. 580817mE, 4251205mN, Zone 15.
- Since the above expresses two possible positions on the earth, the hemisphere may also be specified, e.g. 580817mE, 4251205mN, Zone 15, Northern Hemisphere (Figure 4).
- Many systems abbreviate the above, representing the hemisphere as a single letter, N for northern hemisphere, and S for southern hemisphere, e.g. 15N 580817 4251205.
- CAUTION: IN MANY SYSTEMS, THE LETTER AFTER THE ZONE NUMBER DESIGNATES A LATITUDINAL BAND, NOT A HEMISPHERE.
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Figure 4. Example of position expressed in both Lat/Long and UTM coordinates. Top↑
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POSITIONING IN MGRS---- The Military Grid Reference Systems (MGRS) is an alpha-numeric system for expressing UTM/UPS coordinates. A single alpha-numeric value references a position that is unique for the entire earth.MGRS PDF READ ME
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- The components of MGRS values are as follows:
- (Example: 15SWC8081751205)
- The first two characters represent the 6° wide UTM zone.
- Leading zeros are included so that Zone 9 is 09.
- For polar areas outside the UTM area, these characters are omitted.
- The third character is a letter designating a band of latitude.
- Beginning at 80°S and preceding northward, the 20 bands are lettered C through X, omitting I and O.
- The bands are all 8° high except band X, which is 12° high.
- Outside the UTM are, A and B are used near the South Pole, Y and Z near the North Pole.
- Please See (Figure 5) to the right.
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Figure 5. Military Grid Reference System (MGRS) Top↑
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Figure 6. Military Grid Reference System (MGRS). Top↑
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- The vertical UTM boundaries are horizontal latitude band boundaries form (generally) 6° X 8° Grid Zones. Hence, the first three letters of the MGRS value, e.g. 15S, are referred to as the Grid Zone Designator (GZD).
- The fourth and fifth characters are a pair of letters identifying one of the 100,000-meter grid squares within the grid zone (or UPS area). See (Figure 6) to the left.
- In the Figure 6 sample area, the Grid Zone Designators are shown in brown. The smaller gray letters are the 100,000-meter grid square identifiers. The example point 15SWC8081751205 is located in the square WC near the center of the figure.
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- The remaining characters consist of the numeric Easting and Northing values within the 100,000-meter grid square. See (Figure 7) below.
- MGRS coordinates may be rounded to reflect lesser refinement. For example:
- 15SWC8081751205 is at 1-meter refinement.
- 15SWC80825121 is at 10-meter refinement.
- 15SWC808512 is at 100-meter refinement.
- 15SWC8151 is at 1000-meter refinement.
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- There are two lettering schemes for the 100,000-meter grid square identifiers. Generally, one scheme is used for WGS-84, and the other is used for older ellipsoids associated with the local datums.
- Example: 15SWC8081751205 is on WGS-84. When converted to NAD-27 datum, Clarke 1866 ellipsoid, its value is: 15SWN8083350993
- The 100,000-meter grid square WC for WGS-84 generally coincides with the grid square WN for Clarke 1866. See the section on USNG for further guidance.
- The magenta arrows show how MGRS Easting and Northing values are determined from within the 100,000-meter grid square. The MGRS value of this position is 15SWC8081751205. See (Figure 7) to the right.
- CAUTION: IN MANY SYSTEMS, THE LETTER AFTER THE ZONE NUMBER DESIGNATES A LATITUDINAL BAND, NOT A HEMISPHERE.
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Figure 7. Military Grid Reference System (MGRS). Top↑
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| POSITIONING IN UPS---- The Universal Polar Stereographic (UPS) Systems coordinates are based on a family of two Polar Stereographic map projections, one for each pole.
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- The origin of the UPS coordinate system is at the poles, where X=2,000,000m and Y=2,000,000m. For UPS North see (Figure 8); or for UPS South see (Figure 9).
- The X-axis lies along the meridians 90°E and 90°W.
- Moving from the pole (north or south), X-values (Eastings) increase along the 90°E meridian.
- The Y-axis lies along the meridians 0° and 180°.
- Moving from the North Pole, Y-values (Northings) increase along the 180° meridian.
- Moving from the South Pole, Y-values (Northings) increase along the 0° meridian.
- CAUTION: IN MANY SYSTEMS, THE LETTER AFTER THE ZONE NUMBER DESIGNATES A LATITUDINAL BAND, NOT A HEMISPHERE.
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Figure 8. Universal Polar Stereographic (UPS) North, 100km MGRS Letters Top↑
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Figure 9. Universal Polar Stereographic (UPS) South, 100km MGRS Letters Top↑
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LETTERING/NUMBERING IN UTM & UPS---- The letter after the UTM zone number: is that a hemisphere or a latitudinal band? Since the creation of UTM, developers have interpreted the rules for expressing an earth-wide unique UTM position in one of two ways:
- By including an N or S after the zone number to specify a hemisphere.
- By including the 8° latitudinal band designator (see the section on MGRS) after the zone number.
- Example: The position at 92°W, 38°N, expressed in UTM coordinates, is:
- 587798m E, 4206287m N, Zone 15.
- This reference is valid for two positions on the earth. In order to make it unique for only one position worldwide, i.e. 92°W, 38°N:
- Developer #1 includes an N to specify northern hemisphere:
- Developer #2 includes the 8° latitudinal band designator:
- This situation is causing confusion among users and developers. The two 8° latitudinal bands, from 0° to 8°N and from 32°N to 40°N, are assigned the designations N and S, respectively. These designations are often mistaken for hemisphere designations. NGA updated version of NGA.SIG.0012_2.0.0_UTMUPS contains the authoritative definition of UTM.
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Point of Contact: Coordinate Systems Analysis Team
Phone (314) 676-9124, DSN 846-9124
coordsys@nga.mil
Document last modified September 11, 2014
