Author Topic: Usefulness of resection in map reading  (Read 2161 times)

Offline Mr. Red Beard (UKtheBUNNY)

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Usefulness of resection in map reading
« on: February 05, 2012, 08:58:52 AM »
Usefulness of resection in map reading
Let's say you have a state park map, a protractor and a compass but you don't know where you are on the map exactly. Looking around for significant landmarks that are identifiable on a map you spot a fire observation tower and the peak of a very large hill (larger than others in the area).

On your map you locate each of these identifiable landmarks.
Using a compass you find the azimuth in degrees to each location.

In the map's legend you note the magnetic declination. This is the difference between magnetic north and true north. You will subtract the magnetic declination from the azimuths you recorded.

Draw a line from the landmarks using the angles you calculated from true north. Where the lines cross is your approximate location. Now you know where you are.

This can be done without the magnetic declination and if it's an older map as in several years older the magnetic declination is going to be off anyways and your location is going to be approximate. Don't rely solely on azimuths calculated from the map.  Instead rely more on identifiable features from the map that you can see and an azimuth from your compass to navigate to your destination. 

To do this without a protractor just lay the compass on top of the map using the degrees marked on the compass and eyeball the lines for intersection.

This style of compass would be good for practicing on maps but for azimuths I would recommend a lensatic compass.
« Last Edit: February 06, 2012, 08:04:31 AM by Truik »