Map, Compass & GPS

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

Sunday, June 4, 2017

Is Your GPS Receiver Set-up Correctly?

Setting up the GPS receiver is key to accurate navigation.  The phrase "match the map" is a big first step. 

Therefore, ensure that the GPS receiver's default settings correspond with key factors on the map.

A selection of such factors includes:
  • Set the compass page to working in degrees true rather than magnetic.
  • Position format/cordinate Systems (e.g., UTM Grid or Latitude and Longitude.)
  • Use the correct map datum.

 Note that 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.

Both the compass and GPS receiver must be set to complement each other.  For example, if the hiker has a basic base plate compass (one that cannot be adjusted for declination) then the GPS receiver’s “north reference” must be set to magnetic.  If the hiker has a compass 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 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.  
Now my GPS and compass settings match my topographic map. 

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