First There Was
'Latitude' And '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 simplify the use of
maps, and to avoid the inconvenience of pinpointing locations on
curved reference 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 grid is designed so that 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 New
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.
UTM ZONES
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 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.
Figure 1.
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
UTM Use 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
Figure 2.
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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UTM Roamer
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