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# The Universal Transverse Mercator (UTM) Grid

### Fact Sheet 077-01 (August 2001)

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 || Map Projections || Grids || The Universal Transverse Mercator Grid ||  || Determining a UTM Grid Value for a Map Point || Information || 

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### Map Projections

The most convenient way to identify points on the curved surface of the Earth is with asystem of reference lines called parallels of latitude and meridians of longitude. On some maps,the meridians and parallels appear as straight lines. On most modern maps, however, themeridians and parallels appear as curved lines. These differences are due to the mathematicaltreatment required to portray a curved surface on a flat surface so that important properties of themap (such as distance and areal accuracy) are shown with minimum distortion. The system usedto portray a part of the round Earth on a flat surface is called a map projection.

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### Grids

To simplify the use of maps and to avoid the inconvenience of pinpointing locations oncurved reference lines, cartographers superimpose on the map a rectangular grid consisting oftwo sets of straight, parallel lines, uniformly spaced, each set perpendicular to the other. Thisgrid is designed so that any point on the map can be designated by its latitude and longitude or byits grid coordinates, and a reference in one system can be converted into a reference in anothersystem. Such grids are usually identified by the name of the particular projection for which theyare designed.

### The Universal Transverse Mercator Grid

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| Figure 1. The Universal Transverse Mercator grid that covers theconterminous 48 United States comprises 10 zones—from Zone 10 on the west coastthrough Zone 19 in New England. |

The National Imagery and Mapping Agency (NIMA) (formerly the Defense MappingAgency) adopted a special grid for military use throughout the world called the UniversalTransverse Mercator (UTM) grid. In this grid, the world is divided into 60 north-south zones,each covering a strip 6°  wide in longitude. These zones are numbered consecutivelybeginning with Zone 1, between 180° and 174° west longitude, and progressingeastward to Zone 60, between 174° and 180° east longitude. Thus, the conterminous48 States are covered by 10 zones, from Zone 10 on the west coast through Zone 19 in NewEngland (fig. 1). In each zone, coordinates are measured north and east in meters. (One meterequals 39.37 inches, or slightly more than 1 yard.) The northing values are measuredcontinuously from zero at the Equator, in a northerly direction. To avoid negative numbers forlocations south of the Equator, NIMA's cartographers assigned the Equator an arbitrary falsenorthing value of 10,000,000 meters. A central meridian through the middle of each 6° zoneis assigned an easting value of 500,000 meters. Grid values to the west of this central meridianare less than 500,000; to the east, more than 500,000.

Virtually all NIMA-produced topographic maps and many aeronautical charts show theUTM grid lines.

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### Determining a UTM Grid Value for a Map Point

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| Figure 2. The grid value of line A-A is 357,000 meters east. Thegrid value of line B-B is 4,276,000 meters north. Point P is 800 meters east and 750 meters northof the grid lines; therefore, the grid coordinates of point P are north 4,276,750 and east357,800. |

The UTM grid is shown on all quadrangle maps prepared by the U.S. Geological Survey(USGS). On 7.5-minute quadrangle maps (1:24,000 and 1:25,000 scale) and 15-minutequadrangle maps (1:50,000, 1:62,500, and standard-edition 1:63,360 scales), the UTM grid linesare indicated at intervals of 1,000 meters, either by blue ticks in the margins of the map or withfull grid lines. The 1,000-meter value of the ticks is shown for every tick or grid line. In addition,the actual meter value is shown for ticks nearest the southeast and northwest corners of the map. Provisional maps at 1:63,360 scale show full UTM grids at 5,000-meter intervals.

To use the UTM grid, you can place a transparent grid overlay on the map to subdivide thegrid, or you can draw lines on the map connecting corresponding ticks on opposite edges. Thedistances can  be measured in meters at the map scale between any map point and the nearestgrid lines to the south and west. The northing of the point is the value of the nearest grid linesouth of it plus its distance north of that line; its easting is the value of the nearest grid line westof it plus its distance east of that line (see fig. 2).

On maps at 1:100,000 and 1:250,000 scale, a full UTM grid is shown at intervals of 10,000meters and is numbered and used in the same way.

### Information

For information on USGS products and services, call 1-888-ASK-USGS, or visit thegeneral interest publications Web site on mapping, geography, and related topics aterg.usgs.gov/isb/pubs/pubslists/.

For additional information, visit the  ask.usgs.gov Website or the USGS home page at  www.usgs.gov.

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*This document has undergone official review and approval for publicationsestablished by the National Mapping Discipline, U.S. Geological Survey.  Some figures havebeen modified or added to improve the scientific visualization of information.*

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