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using GPS devices in woods


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We've been caching for a bit of time now and really enjoy it. I'd say we're still pretty new at it though. This weekend we a bit frustrating. Thankfully I resisted the urge to whip my GPS device into the lake we hiking around. Because of the tree cover the coordinates were very erratic and the thing sent us zig-zagging through the brush. It was a very inefficient way to not find a cache.


The questions:

1) Are some GPS devices better suited for use in tree cover? I am currently using a GArmin that is about 5 years old.


2) How does one compensate for the crazy reading one can get in the woods?


I'll have to return the unit I am currently borrowing (good reason to not have sent it to Davey Jones Locker) and will obtain my own unit soon. I'd like to get one that works best in the woods and will be interested to get suggestions.

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Many people say that the helix antenna in a Magellan is better in the woods whil the Garmin type antenna is better around tall buildings and such.


Personally, I get pretty good reception in the woods with my Magellan most of the time. However, it can still bounce around quite a bit under a heavy canopy. The best thing you can do is to get relatively close to the suspect area and look for the best open in the tress, then set the device down. Let it settle for a while and the accuracy will keep getting better. Then take a bearing and distance reading to where the cache should be based on the updated coords. Repeat this procedure as necessary to close in.


Good luck!





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I have an eTrex Legend GPS. It's not the best unit for heavy tree cover, but after a while, you figure out how to compensate for that. It is important to have a lock on the satellites before heading into the woods. It usually maintains the lock as long as I keep the unit upright. Once you know the general direction that you should be heading in, it is better to watch the distance readings than the arrow.




I thought I was wrong once, but I was mistaken.

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The GPS's that use the Quad Helix Ant. are better in the woods, but generally not that much better than the Patch Ant. Just enough to give you that smug feeling.


Most Magellans seem to use the Quad Helix. The Garmin eTrex series uses Patch. Others in the Garmin line do use the Quad Helix also.


Best solution is to use a GPs that can take an external Ant. As a good external Ant. will do more to improve your reception than anything else including upgraditng from a path to a quad helix.


Having said all that. The method I use to figure out where the caches is at is to triangulate.


When I do have reception my GPS will point to a spot and I make a mental note of it. Then as I circle around I'll have another area with reception and the GPS will point to a spot from a different direction. Do this from enough locations (one can be enough if you are used to looking ahead to where the GPS is pointing and thinking about where the cache could be) and you will get a good idea of where ground zero is at even if you can't get reception at ground zero.

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At this type of receiver level the antenna differences really aren't going to make a great amount of difference when compared to multipath and other issues.


Simply using an external and getting it a little higher will help as it can eliminate the user as an additional unwanted obstruction.


Having a good lock first also helps but in essence one works in the woods knowing that things really aren't supposed to work, so many variables.


Cheers, Kerry.


I never get lost icon_smile.gif everybody keeps telling me where to go icon_wink.gif

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I have an eTrex Vista and rarely have a problem in the woods. If it's held flat and out in front of you, its reception is fine. If it does lose it, it regains it quickly. Being that your unit is 5 years old, you could have problems that those of us with newer units don't encounter.


One thing that may be helpful is to bring a compass. Go to an area where you can get a good bearing...a nearby field, or area with a little less tree cover. Square the compass up with your GPS and shoot a bearing. For example, if the GPS tells you the cache is 220 away feet at 150 degrees, just follow your compass at 150 degrees for what you estimate to be 220 feet.


"Give a man a fish, he'll eat for a day. Teach a man to fish, he'll sit in a boat and drink beer all day" - Dave Barry

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At 5 years old is the GPS you were using a 4 channel or a 12 channel? My old 4 channel unit doesn't work nearly as good as my cheapo, but 12 channel, eTrex.

Here in the mountains of Colorado I have had more problems with the signals being bounced around by all the rock formations, especially in some of the canyons. You can be 10' away at one moment and then 110' away the next!



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Once the signal starts bouncing around under tree cover, I start using the distance reading to home in on the cache. The direction arrow becomes useless, and takes a bit of time to correct tiself anyway. Using the distance reading is faster for me.


Like someone eles suggested, take along a compass also. Align it with the direction arrow on the GPS unit and then go the distance indicated. That's how it's done when orienteering with a map and compass, and still works today.


Lone Duck

The Quack Cacher

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We've run into probs from time to time with our GPSr (Magellan SporTrak) losing itself under heavy tree cover. Typically, we'll hike a short distance to a break in the trees, let it find itself again and then all is usually well again. Letting it sit outside for 15-20 minutes and meditate on the sky is good for its demeanor as well.


The kingdom of heaven is like treasure hidden in a field. When a man found it, he hid it again, and then in his joy went and sold all he had and bought that field.---Matthew 13:44


Matt & Julia


To view our online geocaching diary/blog, click here

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I have a Garmin GPS II+ and an Etrex Vista, and I think the accuracy is about the same, even though the old one has a quad helix and the new one has a patch antenna. The advantage of the the Vista is that it tells me it lost the satellites, and the GPS II+ would just keep me wandering around in circles, and I would have to go to the satellite screen to see that I didn't have any sats anymore.


"Wear a smile and have friends; wear a scowl and have wrinkles. What do we live for if not to make the world less difficult for each other?"--George Eliot



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It's actually pretty hard to say which unit may be better suited for use in the woods. If you want fantastic sensitivity, with some pretty decent dead reconning (Or guessing), you want a unit that uses the SiRF IIe/LP chipset. Currently I think you can only get these in mouse or CF type units designed for use with laptops, or PDA's. My Globalsat CF unit is the best I have in the woods by far.


For stand alone units, I've compared my GIII+, Sportrak Map, and eTrex Legend quite extensively. When not moving, and given a couple minutes to sort themselves out, they all seem to get pretty comperable reception. (Finding a good reception spot and using a compass is still the best option I know of) It's rare for one to work when the others don't, and pretty much a toss up as to which one does best, depends on many variables. While moving, the etrex seems to loose reception the most, but it tends to be the most accurate position wise, which is really evident if you play back the tracks over aerial photos with a program such as TOPOFusion. The GIII+ seems fairly balanced reception/accuracy wise with slightly better reception, but slightly worse accuracy. The sportrak tends to be by far the least accurate, unless given a fair amount of time to average the location. Given 20 minutes of averaging or so, it's the most accurate most of the time.


As mentioned, many of the older units were less than full 12 channel receivers, with most of the older Garmins and Magellans being only one or two channel. Just about any newer unit works significantly better than those type units, but virtually any of them can have trouble in trees, canyons etc. Takes time and practice to learn how to make the most of the data they do provide you.

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My biggest problem is being able to use the GPS from my car... Alot of the ones around me are set up so that you park at whatever the coords are... which is a pain in the butt since I'm not familliar with most of the areas that they're in...

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