What Should You Do if a Map Doesn't Match the Terrain?

Verifying Map Accuracy

When a map doesn’t match the terrain, start by checking the map’s scale. Most topographic maps are printed with a scale of 1:24,000 or 1:50,000. If the scale is not indicated, look for a legend or a statement that describes the scale. Verify the map’s datum, which is the reference system used to project the Earth’s surface onto a flat plane. The most common datums used for topographic maps are the Universal Transverse Mercator (UTM) and the State Plane Coordinate System (SPCS). If the map’s scale and datum are correct, proceed to the next step.

Orienting the Map

Look for natural features like rivers, ridges, and valleys that are visible on the map and in the terrain. Use these features to orient the map. For example, if you’re standing near a river, look for the river’s course on the map and adjust the map accordingly. If you’re standing on a ridge, look for the contour lines that represent the ridge on the map and orient the map to match the terrain. Use a compass to take a bearing from a fixed point, like a mountain peak or a landmark, to help orient the map.

Adjusting Your Course

Once you’ve oriented the map, use it to adjust your course. If you’re lost, try to identify a feature on the map that you can use as a reference point. For example, if you see a lake on the map, try to find the lake in the terrain and use it as a reference point to adjust your course. Use a map and compass to take a bearing from the reference point and adjust your course accordingly. Adjust your course in small increments, checking your progress regularly to ensure you’re moving in the right direction. Use a GPS device or a smartphone app to help you navigate and adjust your course, but always rely on your map and compass as a backup.