GPS Electronic Compass

By Blake Miller

Even an experienced hiker will forget about gear that is carried in the field that potentially impacts a digital electronic compass.  While teaching a community college class on land navigation a student asked me what affects a GPS receiver’s electronic compass? This was a great question and offers an opportunity to assess equipment.

In my map and compass (magnetic) navigation class I make a point of discussing the care that should be taken while handling a compass.  A rifle barrel, flash light, radio and other metal and electronic bodies will impact the compass’ magnetic needle.  To see this first hand, move a flashlight next to a compass and the needle will move noticeably.

It never occurred to me that my digital compass would behave similarly.

In November while elk hunting and camping east of Oregon’s Cascades mountain range, I decided to check this out.

The test platform was my Garmin 60CS.

I found that my electronic compass would react to interference.  That said, reaction was based on overt action on my part.

For example, moving my Inova flashlight tight up to the receiver elicited a varied response.  The reaction was immediate; the electronic compass swung roughly between 20°- 90°.

My rifle barrel caused a 10°-20° deflection but only after deliberate and perhaps unrealistic contact.

I got the same results with my cell phone.

My analysis is that the electronic compass’ reaction to stimulus was possible but only after deliberate contact. The electronic compass is not nearly as sensitive as a magnetic compass.

My advice, just keep this in mind and watch what’s around the GPS receiver.