Do we need a new GPS?

[+lady and laddy bugs]

My husband and I have been geocaching for about a month now. We were introduced to it by R R Mateys - Thanks!

But my question has to do with our GPS. My husband is a private pilot and has two GPSs he uses in flying. One is older, a Garmin 55 and the other newer one is a Garmin 90. The problem is on the ground the coordinates do not seem to be stable. The units work to get us withing .03 miles of a cache but then because the coordinates seem to be changing even if we are not moving we sometimes are walking around the cache site for 15 or 20 minutes before we can zero in on the spot. Usually when we have found the cache and have made entries and exchanges, by that time our GPS has caught up with us and the coordinates match and the distance is down to .00 miles.

Is this how all GPS units work? Or are we just too impatient to wait for the GPS unit to catch up with us? The units work great in a airplane, so we thought they should be fine at our slower walking speed.

[+sbell111]

I am not completely familiar with the 55 and 90, but I think I know why you're having problems.

 

These units are older aviation models which track up to 8 satellites. They work fine while flying because they are able to keep their lock on the satellites. On the ground, however, they have problems. You are losing satellites due to the interference of trees, buildings, terrain, et al.

 

When the unit loses signal, a few things happen (depending on the unit). 1) Your location will temporarily freeze. This results in the GPSr showing you to be further away from the prize than you actually are. 2) The GPSr may attempt to estimate your course while it reacquires the satellites. This would show you moving at a constant course and speed when you may have stopped or changed direction. 3) As you lose individual satellites, the accuracy will suffer. As the unit loses and regains satellites it gives it's 'best guess' of your location. This will tend to move your location around a bit even though you are not moving.

 

As you've found, you can still use these units for geocaching. It just adds a level of difficulty that many of us don't have. My advise is this: If you really enjoy geocaching (and can rationalize the expense) buy another GPSr. A basic eTrex can be purchased for about $100. I bought my GPS3+ for about $150 on eBay.

 

Good luck and have fun!

[OFF RODE]

As stated above these are aviation units...and old...Besides 8 channels they arnt paralell receivers ( receive more than one sat at a time ). Fine if you are moving 150 MPH in a rather constant heading with a clear view of the sky...but walking at 1 mph in tree cover etc. it rather lags a bit. So if you arnt in a hurry it will work...bur rather frustrating...Id look at a basic etrex yellow for around $100

 

"You've got to be very careful if you don't know where you're going, because you might not get there." Yogi Berra

[+Navdog]

Just remember that any GPSR, even a new one, Will display a certain amount of coordinate "drift" when trying to zero in on a cache location, especially under tree canopies. It is all part of the challenge in finding the cache. And you shouldn't expect to zero out your coordinates at every cache.

 

The adventures of Navdog, Justdog, and Otterpup