First There Was 'Latitude' & 'Longitude' Map Coordinates
- Latitude (parallels of latitude) and Longitude (meridians of longitude) make up a system of reference lines used to identify points on the curved surface of the earth.
Then Came Flat Thinking Grid Technology!
- To put navigation into a human perspective, and make is easy to use maps and avoid the unnatural task of pinpointing locations on curved reference lines (latitude and longitude lines), cartographers superimpose on the map, a rectangular grid consisting of two sets of straight, parallel lines, uniformly spaced, each set perpendicular to the other. This new grid is designed so any point on the map can be designated by its latitude and longitude or by its grid coordinates, and a reference in one system can be converted into a reference in another system. Such grids are usually identified by the name of the particular projection for which they are designed.
The Modern Universal, International Map Standard - 'UTM'
- The National Imagery and Mapping Agency (NIMA) (formerly the Defense Mapping Agency) of the United States, adopted a special grid for military use throughout the world called the Universal Transverse 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 consecutively beginning with Zone 1, between 180° and 174° west longitude, and progressing eastward to Zone 60, between 174° and 180° east longitude
- In each UTM zone coordinates are measured towards the east then the north, in meters
- Easting Value
- A central meridian through the middle of each 6? zone is assigned an easting value of 500,000 meters. Grid values to the west of this central meridian are less than 500,000; to the east, more than 500,000.
- Northing Value
- The "Northing" values are measured continuously from zero at the Equator, in a northerly direction.
South of The Equator
- To avoid negative numbers for locations south of the Equator, NIMA's cartographers assigned the Equator an arbitrary false "northing" value of 10,000,000 meters. therefore, subtract the northing number from 10,000,000 meters for the distance of a coordinate south of the equator.
The Universal Transverse Mercator grid that covers the conterminous 48 United States, comprises 10 UTM zones; from zone-10 on the west coast through zone-19 in New England.
UTM, Today's Map Standard!
Virtually all NIMA-produced topographic maps and many aeronautical charts include the UTM grid lines. Modern government's topographical maps now include the UTM grid.
The UTM map coordinate system can be used with map and compass navigation; map and roamer measure; map, compass and roamer measure device; with most GPS receiver systems set to use UTM as the location data display format; and with GPS, map, compass.
Today's Modern Navigator's Standard Tools
UTM Roamer Scales
1 Map Tool, All World UTM Roamer Scales For ALL World Standard Map Scales !
Compass With UTM Roamer Scales
UTM Roamer Scale For All International Standard Map Scales
Using UTM Is Easy!
Finding A Set Of UTM Coordinates For Any Given Point On A Map:
- Determine The UTM Zone Number From Map
- Determine The UTM Zone Letter From Map
- Measure Distance In Meters To The Point, Starting From The Bottom Left Corner Up To The Point; Called "Northing"
- Measure Distance In Meters To The Point, Starting From The Right Edge Of The Grid To The Point; Called "Easting"
A Set of UTM Coordinates, Identifies One Intersecting Point On The UTM Grid, Which Gives A Unique Address To An Exact Point On The Surface Of The Earth!
When working with UTM grid zones, areas are referenced by quoting the zone number (longitudinal direction) first, followed by the zone letter (latitudinal direction). Example: The UTM Grid Zone for the southern end of South America is 19F.
Next, The UTM Coordinates indicate the distance from the Equator. When referring the older Earth-coordinates method, this would be like a latitude value.
Next The UTM Coordinates indicates the "Easting" value. When referring the older Earth-coordinates method, this would be like a longitudes value. Central meridian of each zone has an Easting value of 500 km. Within a zone, the Easting values increase eastward (measurements to the right).
Northing and Easting values are marked on the sides of a map with the UTM projection.
Determining The UTM Coordinates For A Point On A Map
The following methods work with all international maps.
Working With U.S.G.S Topographical Map Scales.
The UTM grid is shown on all quadrangle maps prepared by the U.S. Geological Survey (USGS) Department of the U.S. government.
On 7.5-minute quadrangle maps (1:24,000 and 1:25,000 scale) and 15-minute quadrangle maps (1:50,000, 1:62,500, and standard-edition 1:63,360 scales), the UTM grid lines are indicated at intervals of 1,000 meters, either by blue ticks in the margins of the map, or with full 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.
Map Grid Lines: 1,000 by 1,000 Meters
The grid value of line A-A is 357,000 meters east. The grid value of line B-B is 4,276,000 meters north. Point P is 800 meters east and 750 meters north of the grid lines; therefore, the grid coordinates of point P are north 4,276,750 and east 357,800.
To use the UTM grid, you can place a transparent grid overlay on the map to subdivide the grid, or you can draw lines on the map connecting corresponding ticks on opposite edges. The distances can be measured in meters at the map scale between any map point and the nearest grid lines to the south and west. The northing of the point is the value of the nearest grid line south of it plus its distance north of that line; its easting is the value of the nearest grid line west of 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 10,000 meters and is numbered and used in the same way.
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U.S.G.S. Definition of Universal Transverse Mercator Grid System (UTM)
The Universal Transverse Mercator Grid System (UTM) provides rectangular coordinates that may be used to indicate locations of points on the surface of the Earth. UTM involves linear measurements, and the unit of measure is the meter. A point is located by specifying a hemispheric indicator, a zone number, an easting value, and a northing value.
UTM is designed for world use between 80 degrees south latitude and 84 degrees north latitude. The globe is divided into narrow zones, 6 degrees of longitude in width, starting at the 180 degree meridian of longitude and progressing eastward. The zones are numbered 1 through 60. Each zone has, as its east and west limits, a meridian of longitude. Each zone also has a central meridian passing through the center of the zone. The location of any point within a zone is given in relation to the central meridian within that zone and the equator. The system zone yields positive values for the identification of a point on the earth's surface by first assigning numeric values to the equator and the central meridian. Then, a point's north-south location is obtained by either adding or subtracting the point's distance north or south of the equator. Similarly, a point's east-west location is obtained by either adding or subtracting the point's distance east or west of the central meridian.
A value of 500,000 meters is assigned to the central meridian of each zone in order to avoid negative numbers at the west edge of the zone. The values increase from west to east. For north-south values in the northern hemisphere, the equator is assigned 0 meters, and the numbers increase toward the north pole. In the southern hemisphere, the equator is assigned 10,000,000 meters, and the numbers decrease toward the south pole.
On a map, appropriate values for the easting and northing of a point are determined relative to labeled grid lines. A point on the equator is assigned a value of zero for its northing and is treated as if it were in the northern hemisphere. A point on a boundary meridian is assigned the zone number for the zone to the east of the point.