I know the compass needs to be calibrated with a battery change, but didn't realize it needed to be calibrated every time it's turned on. Just one more reason to leave it turned off.

For most practical purposes in wilderness navigation, a error of this magnitude is usually rather insignificant, say in climbing to a 10,000 foot high pass, or a 13,000 high mountain.

The geoid must correspond to the datum in my neck of the woods. I recall reaching a benchmark - holding the GPS receiver I noted that it was reading three feet high - then I realized that I was holding it at waist level, about three feet above the brass cap marking the benchmark.

True enough. But then again, if I'm using a GPS, I usually can find the pass or peak without needing an altimeter of any kind.

Truth be told, while I carry a both a GPS (with electronic compass and barometric altimeter) and a regular magnetic compass, most of the time I'm not using them. In the mountainous country I'm usually in, I can generally eyeball my location well enough from map and terrain. However, as I believe you noted somewhere above, there are exceptions (night, fog or whiteout, thick brush, flat terrain, etc). My experience has been that while I usually don't need the GPS and compass......when I do need them ....I need them really really bad! Which is why I carry them.

I guess that is the same in both Arizona and Alaska. I think in over twenty years in Arizona, I only pulled out my compass twice, both times in stormy conditions and thick fog, but without it I would still be wandering around....

With a GPS these days, it is nice to look and see that you have gained half your altitude or whatever, especially if you are in the midst of a nice thick forest with no long views, and that you have already traveled 8.32 miles of the 13.2 you need to cover. Not vital to know, usually, but still fun.

I suspect that I'm one of the few folks you'll find here that actually PREFERS my GPS's to have electronic compasses. My reason is simple - this allows the GPS to continue to "point" to a waypoint even when I'm standing still.

Yes, I can use a magnetic compass, and carry one (or more) with me, and know well how to use it, but I tend to prefer tools that keep things as "automated" (simple) as possible so that if I'm tired or confused the arrow will be pointing in the correct direction, I can make proper decisions. Think of it something like the recommendation to be able to use gear one-handed - knife, light, PLB, ...

Yes, I know that a GPS can fail, or the batteries can go dead. I've had both happen to me. The former with a Garmin Nuvi while driving through a thunderstorm in the middle of an area in Detroit that I was completely unfamiliar with (uh oh), and the later while doing Geocaching with a group of Girl Scouts (its embarassing to borrow a few spare batteries from a Girl Scout - sigh). Typically I carry extra batteries, but in that case they were left at camp.

Then again, I'm also a person who will only accept adjustable declination on my magnetic compasses. A declination scale or doing the mental math is not something I want to do.

I rarely calibrate the compass in my Garmin GPSMAP 60CSx, and it points correctly. Heck, recalibrating it is a pretty simple matter - walk around in a little circle until it beeps - simpler than using a magnetic compass.

I'm not so sure that there is a power consumption concern with the electronic compass. A while back a few people on the geocaching.com forum did some direct power consumption measurements, and here are the results he posted (the power consumption for the electronic compass was negligable). The big power drain was the backlight - if used. The best way to minimize power consumption is to only turn it on the GPS when truely needed - as opposed to keeping it on to capture track information:

Garmin eTrex Vista HCx (fresh alkaline batteries)
69 mAmps - backlight off, WAAS off, electronic compass off
70 mAmps - WASS turned on
70 mAmps - WAAS on, electronic compass on
98 mAmps - GPS radio off
235 mAmps - backlight on

Garmin eTrex Venture Cx (rechargable batteries):
77.4 mA - GPS radio on, Backlight off
144 mA - GPS radio on, Backlight medium
220 mA - GPS radio on, Backlight high
48.6 mA - GPS radio off, Backlight off
108 mA - GPS radio off, Backlight medium
185 mA - GPS radio off, Backlight high
No difference WAAS on or off
From http://forums.groundspeak.com/GC/index.p...p;#entry3123403

If true, it would appear that the electronic compass has been improved immensely wrt power consumption. That's good to know. Thanks.

Not always true. More modern GPSr have multi-axis compasses and give accurate direction even when motionless. My Garmin 62s for example. I do have to remember to recalibrate the compass after every battery change tho. But no matter what I always keep at least one magnetic compass with me.

I was referring to GPS as the satellite nav system, not the particular electronic gadget in one's hand. "GPS" has started to have varying meanings as onboard maps, onboard food & gas & whatever databases start to be delivered in the gadget.
Some GPS gadgets have a flux-gate compass, some don't. Some have McDonald's restaurant locations, some don't.

Some even have cellphones attached to them!

That doesn't sound right. The reason a calibration is necessary after switching batteries is because of the lack of memory retention without power. I'll have to recheck my manual to verify your statement. [Note: Mine says to recalibrate after moving long distances, large temperature changes or battery changes. To what degree is goes out of calibration I don't know but I suspect it is much less that what people think.]

The barometer/altimeter can be set to known air pressure levels but that's a hassle unless you have an accurate barometer to compare it to. That makes it superior to the gps signal. I use the gps signal to give me the altitude because it is more convenient. Remember though that with the gps signal, the vertical component of the unit is subject to 1/4x the accuracy of the horizontal component. A 3 metre horizontial accuracy equates to a max of 12 metre vertical accuracy. That's probably one reason why people have doubted it's usability.

Between models, even with the same manufacturer the accuracy may vary. The barometer on my 62s indicates an elevation at least 15 less than my 60CSx and this is borne out in real life comparisons to benchmarks. My 62s autocalibrates the altimeter on every turn on. It can be set to record air pressure only when on or alternately even when off at some battery expense.

I have discovered that the trip computer odometer on my GPS (Garmin Extrex Vista H) can be off by a substantial amount, especially if I am walking slowly, like in hilly terrain. The distance reported in basecamp seems about right most often. I have had the numbers vary by 50% on occassion. I no longer use the trip odometer for much of anything. It also grossly overstates the amount of stationary time versus moving time.