Map, Compass & GPS

Map, Compass & GPS
Wild flowers along Fall Creek on the way to the Green Lakes - Oregon

Thursday, July 9, 2015

Is your GPS set up correctly?  Does your GPS's electronic compass match with your magnetic compass?

There are two considerations that need to be taken into account.

First, every time the GPS receiver’s batteries are replaced, the electronic compass needs to be calibrated.  It’s a simple process that requires a quick check of the owner’s manual.

Second, both the compass and GPS receiver must be set to complement each other.  For example, if the hunter has a basic base plate compass (one that cannot be adjusted for declination)  then the GPS receiver’s “north reference” should be set to magnetic.  If the hunter has a compass that can be adjusted for declination then the receiver should be set to true north.  If compass and GPS receiver don’t match then the bearing information may be as much as 10° to 20° off.  That is not good.

I carry a Sylva Ranger style compass that can be adjusted for declination.  Before leaving home I visit to verify the correct declination for my planned hunt or hiking location.  With that information I adjust the compass.  Yes, the magnetic needle still points to magnetic north but the rotating dial provides degree/azimuth information in degrees true.  I’ll then set my GPS receiver’s “north reference” to true north.

Now my GPS and compass settings match my topographic map. That is the best way to do it.

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