How to Get UTMs on a Topographic Map

For many years hikers, hunters and other outdoor sports enthusiasts have used the topographic maps published by the U. S. Geological Survey as the reference standard for locating themselves. Now that hand-held Global Positioning System (GPS) units are inexpensive and widely available, they have begun to replace paper maps. In roadless areas, however, reaching a specific location with a GPS may still require you to describe a location with map coordinates such as the Universal Transverse Mercator (UTM) system. With a topographic map, a calculator and a ruler you can calculate a pair of UTMs for any point on the map.

Things You'll Need

  • Topographic map
  • Pencil and paper
  • Ruler
  • Calculator
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Instructions

    • 1

      Locate the UTM grid printed on the topographic map. Grid lines form squares on the map, each of which is 1000 meters on a side. All lines are labeled at the map edges, usually with one or two small numbers and two large numbers. At least one label on every edge adds three zeros, followed by the letter "m" and one of the letters "N," "S," "W" or "E."

    • 2

      Locate the point of interest on the topographic map and circle it with a pencil line.

    • 3

      Draw a square on a piece of paper to use as a reference. Find the four UTM lines that make a box around the location and follow them to the edge of the map. Circle the labels where the four lines meet the edge and write their values along the edges of your reference square. If a label does not end in three zeros and a letter, look for a label on the same side that does (example: 412000mN) and include the zeros and directions.

    • 4

      Measure the width and height of the square on the topographic map with a ruler. Squares along an edge may not be complete; if this is the case, measure an adjacent, complete square. Record the height and width of the square on the drawing.

    • 5

      Measure the distance from the location to the nearest north-south (top to bottom) line to the right on the map. Divide the distance by the width of the square and multiply by 1,000 (example: 1.0625 / 3.125, = 0.34 times 1000 = 340). Call this number, the distance from the point to the north-south line in meters, E.

    • 6

      Calculate the east-west, or X, UTM coordinate: if the north-south grid line is labeled with a W (example: 297000mW), add E to the number (example: 297000+340 = 297340mW). If the line is labeled with an E (example: 297000mE), subtract E from the number (example: 297000-340 = 296660mE).

    • 7

      Measure the distance from the location to the nearest east-west (left to right) grid line below the point on the map. Divide the distance by the measured height of the square and multiply by 1,000. Call this number, the distance from the point to the east-west line in meters, N.

    • 8

      Calculate the north-south, or Y, UTM coordinate: Add N to the number on the label of the next east-west line south of the point (example: 3912000+340 = 3912340mN).