Map, Compass & GPS

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

Tuesday, May 29, 2012

Steps to Improve Compass Accuracy

To improve accuracy I’d suggest:

  • Ensure the compass is “on the mark” in terms of correct declination adjustment, the setting of the Direction of Travel Arrow and the alignment of the compass to the bearing (are you really pointing in the right direction.)
  • Pick the best land marks to work with such as pinnacles and spires and pronounced land marks; the choices may be limited.

There are several factors that impact accuracy that the hiker may have no control over but should be aware of.  Some of these include:

  • The quality of the hiker’s vision.

  • Polarity of the compass’ magnetic needle – does it point in the right direction? Polarity may change over time such that the magnetic needle my no longer work accurately.
  • Smooth movement of the magnetic needle.
  • Alignment of the compass dial to the compass housing.
  • Local attraction – Similar to declination, local attraction is magnetic interference unique to a specific location.  It may be caused by buried metal objects or an unusually high concentration of iron or nickel in the ground.
Navigation is not hard but it does take practice; it is a perishable skill.  I recommend to those in my classes that a minimum of two weeks before a backcountry trip that the GPS, map and compass goes everywhere with them.  Practice in the field or at the park.  Take the time to compare the three with what is seen. 

When in the wilderness compare both map and compass with a GPS when possible.  Hiking companions should compare their work too.

Familiarity with your equipment will make you a more skilled advocate for your safe return.

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