How to Do a Resection With a Map and Compass

If you can locate two or more distant terrain features on a map, you can use resection to pinpoint your exact location.

Things You'll Need

  • Protractors
  • Mechanical Pencils
  • Scrap Notebook Papers
  • Base Plate Compasses
  • Straightedges
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Instructions

    • 1

      Pinpoint a distant feature of the terrain such as a hilltop, stream or road junction on the map.

    • 2

      Using a compass, measure the exact magnetic direction from where you are to the feature.

    • 3

      Convert the magnetic direction to a map north direction by subtracting the magnetic variation provided on the map (there should be a small diagram on the map that helps you accomplish this).

    • 4

      Calculate the reverse direction of the map north direction (180 degrees from map north).

    • 5

      Put the center point of a protractor on the exact map location that you sighted to with your compass.

    • 6

      Line up the 0-degree mark on the protractor with map north.

    • 7

      Make a mark on the map next to the protractor at the number of degrees of the reverse direction.

    • 8

      Remove the protractor and draw a long line with a straightedge and mechanical pencil from the pinpointed distant terrain feature through the mark you just made.

    • 9

      Double-check your calculations. You are located somewhere on this line.

    • 10

      Pinpoint a second distant feature and repeat steps 1 through 8. You are located where the two lines intersect.

    • 11

      Repeat the process with a third distant landmark to confirm your work, if possible.

    • 12

      Check your calculations if there is a large difference between the points of intersection.

Tips & Warnings

  • Practice resection before you are actually lost.

  • If you are on or alongside a linear terrain feature, such as a trail or river, you can pinpoint your location by finding the point at which one line of resection intersects the linear terrain feature.

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