Compass VS. GPS - the winner is...

I love my GPS devices. However, as a compass, they stink.

I was out with the kids over the weekend, and was having some fun with some orienteering. Just for the heck of it, I took my son's GPS and set it to compass. Just to make sure it had a good read, I slowly walked in a circle about 40 meters in diameter, then set the GPS down.

Have a look at the reading of Sunnoto vs. the Magellan GPS. (the SUnnoto is correct, the GPS "north" indicator is the dark line on the display.



Suffice it to say that the $20 compass kicked butt on the $100 GPS when it came to basic direction finding.

Keep both in your kit.

The compass in my Geko 301 stays off because it's just too hard on battery life, but once it's adjusted (hold the compass and slowly turn 360*, the compass feature works well. I'd trust your picture more if the compass wasn't so close to the GPS. The needle on your compass (a magnet) will effect the reading of the GPS. For these tests I usually use a third inert object and put the compass' next to it in turn rather than putting them side by side.

I'd just like to point out that I would not have posted the image if I hadn't seen WILDLY inaccurate readings from the GPS when it was all by itself. I mean, I KNOW which way north is, I was in a local park, and I can assure you that the compass was correctly pointing magnetic north, and the GPS was supposedly set for Magnetic north too. Just look at the heading on the GPS vs. the compass!

From what I can tell your GPS is a Magellan eXplorist 100, which does NOT have an electronic compass, though I really like the orange case AND the fact that you're out with your kids.

GPS's without an electronic compass rely only on movement to determine direction. The faster the movement, the better its ability to determine direction, though I've found even at a walking pace they do surprisingly well. Once you stop, the GPS's compass is dumb - it either stops displaying the compass altogether or only shows the most recent direction observed.

The Geko 301 mentioned by someone else has a +/- 2 degree accuracy, which is pretty good - close to many (most?) magnetic compasses.

Keep having fun out there!

Checking Magellan's product page:
http://www.magellangps.com/products/product.asp?segID=355

If color is any indication you have a model 100.
The feature list for the orange Explorist 100 does not mention magnetic compass.

You do not have a compass in your GPS.

What is presented is a heading indicator. In order for the GPS to calculate direction it requires satellite fix info and motion of at least walking speed if not faster. (the speed shown is zero)

This is not a valid comparison and demonstrates that one really, really must understand their equipment before relying on it.

I use magnetic compass with my GPS all the time. The GPS tells me the heading to go to my waypoints. The compass tells me where that heading really is.

This comparison is like looking at the directional gyro in an airplane that's been parked for a week and comparing to the whiskey compass. It's an invalid comparison.

unimogbert

Man, I'm normally such a clear writer.

I think I didn't explain that I WAS walking and I was trying to figure out why the compass was so off. When I took the picture, I had just finished walking in a 40 meter circle and while the compass dutifully pointed magnetic north, the GPS did no such thing.
At the end of the walk, I set the GPS down and then the compass. The needle of the compass remained stable, the compass indicator on the GPS also remained stable - still pointing the wrong way as it was when I was walking, with a 3D fix (9 tracked). I used to sell these things, I know all about what a magnetic vs. a non-magnetic compass is, i think that something is screwy in the 100, which is/was always a piece of crap. I have the 60c by Magellan and that's just a great unit WITH a decent compass.

Yes keep both in your kit.
GPS units tell you where you are, compasses tell which way to go.
The flux gate compasses in GPS units are at best 5 degrees and only if you have calibrated them (every time you change batteries).
Practice with map and compass, check results with GPS.
Much can be said for the old compass, it's really a lot of benefit for not much cost. GPS's are great for position though.

How does the heading indicator (not compass) read when you walk in a straight line?

Martin, maybe you're right.... maybe you've got a problem with that GPS... I mean, that particular unit .

If you used to sell them, you know the Mag 100 is a solid, basic unit. I've used one many times at work, they're just fine. Yours may be buggered or something.

Glad it was a comms issue rather than lack of understanding. I haven't used any Magellan products.

My Garmins haven't given me any surprises like this but it seems possible that a non-optimum satellite constellation combined with slowwalkng speed could confuse the algorithm that does the calculation.
Or the unit is broken in some way.

Compasses are cheap and reliable. This is good warning to always check the tech gadget against the stone-simple gadget.

unimogbert

I carry a Garmin eTrex Vista Cx and a simple Sunnto compass. With a 2 gb card, the Vista can hold City Navagator maps for the entire US in a handheld package. However, I can't look at the map page and the compass page at the same time while driving and the GPS does not get an accurate directional position while navigating until you have moved for several feet. Thus, I use the compass to dertermine the initial directionI need to head until the GPS "gets it bearings."

As others have pointed out, GPS units with electronic compasses (such as the eTrex), are very accurate, but alas, are dependent on batteries which can let you down at the worst possible moment.

So, for my money, there is no winner. The prudent thing to do is to carry both.

Craig.