U.S. Department of the Interior, National Park Service
INSTRUCTIONS FOR DETERMINING UTM REFERENCES
The Universal Transverse Mercator (UTM) Grid System provides a simple and accurate method for recording the geographic location of a historic property. The UTM Grid System has a number of advantages over the Geographic Coordinate System of latitude and longitude, particularly speed, precision, and the use of linear, metric units of measure. Determining UTM references, in its simplest application, requires only a straightedge, a coordinate counter, and a sharp pencil as working tools. (The coordinate counter, a plastic measuring tool, may be obtained from J & J Reproduction and Drafting Supplies, Inc., 9017-F Mendenhall Court, Columbia, MD 21045, 1-800-825-2635.)
The UTM grid references may be determined from many USGS quadrangles published since 1950, and all published since 1959. If there is no USGS map with UTM ticks for a location, enter the geographic coordinates for the location of the property using latitude and longitude or a State's grid system.
In the UTM system, the Earth is divided into 60 zones, running north and south, each 6 degrees wide. Each zone is numbered (most of the USA is included in zones 10 through 19), beginning at the 180-degree meridian near the International Date Line. On a USGS map, each zone is flattened and a square grid is marked off in meters superimposed upon it. Any point in the zone may be referenced by citing its zone number, its distance in meters from a north-south reference line ("easting"), and its distance in meters from the Equator ("northing"). These three figures - the zone number, easting, and northing - make up the complete UTM grid reference for any point and distinguish it from any other point on Earth.
The simplest method of determining a UTM reference is based on drawing part of the UTM grid on the map, and measuring from the grid lines to the point. It requires the following:
To measure each point , follow these steps:
1. Draw a line from the top of the map to the bottom (north to south), connecting theUTM ticks of the same value directly west of the point, that is the ticks with the highest easting value west of the point.
2. Draw a line from the left to the right side of the map (west to east), connecting the grid ticks of the same value directly south of the point, that is the ticks with the highest northing value south of the point. This line will intersect the north-south line somewhere to the southwest of the point.
3. Record the zone number on a worksheet. This number appears in the lower left corner of the map.
4. Record on a worksheet the numbers given by the map ticks through which the lines have been drawn. These are the first three digits of the easting value and the first four digits of the northing value.
5. Locate the scale on the coordinate counter matching that of the map, eg. 1:24,000. Align the counter on the map so that:
a. the side of the scale that reads from right to left lies along the east-west line.
b. the side of the scale that reads from left to right passes directly through the point.
(Check the alignment to be sure that it is precise.)
6. Read the coordinate counter scales, right to left for the easting and upward for the northing to get a measured value in three decimal places. In each case, enter the measured value on the worksheet after the number recorded in step 4.
7. Check the readings--are all figures in the correct decimal place? The easting will have six digits and the northing seven.
8. Check the figures for accuracy by remeasuring.
9. Be sure the following is given: zone number, easting, and northing (Z,E,N).
10.Enter the each grid reference on the USGS form (in pencil only) and in section 10 of the registration form (see instructions in Chapter III, section 10). One UTM reference is required for properties less than ten acres; three or more references for larger properties.
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