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Having some problems with tree cover... any suggestions?


jam4ar
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Hello folks,

 

I'm a new cacher and am having some troubles while caching. I have a Venture HC.

 

The problems occur when I go to find a cache in a wooded area. Shortly after I step into the trees the GPS's accuracy goes to pot. and it often will tell me the cache is in places I know it isn't. I've been standing right beside a cache before and it told me it was 40 feet up the hill. It also does things like giving me a bearing of S, a Heading of N but the distance to cache is going down. I know loss of accuracy can't really be avoided in the trees but I'm just wondering how I can better deal with it and not end up walking around with both me and the GPS confused.

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You have to remember, on a good reception day your accuracy is 3 meters besides what your gps accuracy reading is. When/if you have 0 feet accuracy reading you can still be 3 meters off. Now I can come by a minute later and have the same unaccuracy so your looking at a circle circumference of all that added together on a good reception day. This is where your geosense of where/how a cache could be hidden should take over, it comes with experience and is part of the challenge.

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Hello folks,

 

I'm a new cacher and am having some troubles while caching. I have a Venture HC.

 

The problems occur when I go to find a cache in a wooded area. Shortly after I step into the trees the GPS's accuracy goes to pot. and it often will tell me the cache is in places I know it isn't. I've been standing right beside a cache before and it told me it was 40 feet up the hill. It also does things like giving me a bearing of S, a Heading of N but the distance to cache is going down. I know loss of accuracy can't really be avoided in the trees but I'm just wondering how I can better deal with it and not end up walking around with both me and the GPS confused.

 

Remember a few things:

 

1. Your GPS will work best when you have an unobstructed view of the sky.

2. You need a reading from 3 satellites to get a fix.

3. You cannot always assume that coords you are given are always correct.

4. If you are inside 30 feet, it is time to start using your eyes more than your instrument. IE your geosense.

 

There are chipsets that work better under cover. I have owned three GPS units and the Garmin 60CX outperformed the Magellan Color and the Garmin Etrex hands down. If you do a lot of hiking in areas with obstructed view, this is a unit worth considering.

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Another thing to remember.

 

If someone placed it and had +/- 20ft accuracy and you arrived with +/- 20ft accuracy your total inaccuracy can be as high as 40ft without a problem. If they person who placed it didn't have a high sensitivity receiver or had some multi-path error obviously the error gets worse from there.

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What I do sometimes, if I can, is I'll step back out into an open area, and let the accuracy get better, and see which direction it's pointing. Then I'll move to a different clear area a little ways off and on a different bearing from the cache, and do the same thing, then just try to get to the point around where those two intersect. It's not perfect, but it can help.

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Another thing to remember.

 

If someone placed it and had +/- 20ft accuracy and you arrived with +/- 20ft accuracy your total inaccuracy can be as high as 40ft without a problem.

Umm.... no.

 

That's not how errors work. It is pretty unlikely for two 20-foot EPEs to cause a 40 foot error, especially with how the EPEs are calculated in consumer GPS units.

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What I do sometimes, if I can, is I'll step back out into an open area, and let the accuracy get better, and see which direction it's pointing. Then I'll move to a different clear area a little ways off and on a different bearing from the cache, and do the same thing, then just try to get to the point around where those two intersect. It's not perfect, but it can help.
That's the best way to do it. It's more of a challenge but the challenge makes it more fun.
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Thanks for all the replies! While I'm not ready to blame the GPS yet.. I mean.. I know it's not my fault for the loss of accuracy but if other people have success with the eTrex line then I can as well. A friend of mine has a garmin with the helix type antenna I'll give it a go next time we're out caching and see if I think it's better.

 

The chainsaw sure does sound like it'd work but I'm not sure I could get away with cutting down trees in national forests very long.

 

Moving out of the covered area is what I usually do and move along the tree line until I get a straight line to the coords then try to just move straight counting my steps and estimating how far I've traveled until I think I'm near it. Works sometimes.. sometimes I have to do it a few times.. and sometimes I just get confused.

 

Guess it's just part of the game. I still have fun looking..

 

See you on the trails!

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Thanks for all the replies! While I'm not ready to blame the GPS yet.. I mean.. I know it's not my fault for the loss of accuracy but if other people have success with the eTrex line then I can as well. A friend of mine has a garmin with the helix type antenna I'll give it a go next time we're out caching and see if I think it's better.

 

The chainsaw sure does sound like it'd work but I'm not sure I could get away with cutting down trees in national forests very long.

 

Moving out of the covered area is what I usually do and move along the tree line until I get a straight line to the coords then try to just move straight counting my steps and estimating how far I've traveled until I think I'm near it. Works sometimes.. sometimes I have to do it a few times.. and sometimes I just get confused.

 

Guess it's just part of the game. I still have fun looking..

 

See you on the trails!

 

another question, is does that unit make use of WAAS, and if so, do you have it on? It doesn't do me a lot of good most of the time, because I don't have many ground correction stations that my unit can pick up, but on the occasions where it's worked, it's worked _GREAT_.

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Yea I have WAAS enabled but I can't tell any difference.. What do you mean stations your unit can pick up? I thought they were another set of satellites..

They are. He is confused. Maybe he meant something like this:

 

If you are outside the US, the WAAS corrections don't work as well because WAAS uses fixed ground stations in the US to calculate the corrections that are sent to your GPS via the geostationary satellites. Some of the corrections depend on location, while others do not. The ones that do won't be correct if you are, for example, in Europe.

 

Not to worry; your GPS will adjust for that automatically.

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Yea I have WAAS enabled but I can't tell any difference.. What do you mean stations your unit can pick up? I thought they were another set of satellites..

They are. He is confused. Maybe he meant something like this:

 

If you are outside the US, the WAAS corrections don't work as well because WAAS uses fixed ground stations in the US to calculate the corrections that are sent to your GPS via the geostationary satellites. Some of the corrections depend on location, while others do not. The ones that do won't be correct if you are, for example, in Europe.

 

Not to worry; your GPS will adjust for that automatically.

Europe has their own system called EGNOS, which works the same way (and on the same frequencies, etc.) as WAAS, so enabling WAAS will allow your receiver to use EGNOS satellites when they're visible (i.e., in Europe). In general, it's a good idea to leave it on unless you have compelling evidence that it's making your accuracy worse.

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One thing you can do to increase your odds a bit when going after a cache is to look at the satellite images of the area before you go. This can trigger some ideas when you get to the cache site. (Example: About how far from the creek). It does not help much in heavy wooded areas, but it may.

 

Second: head to an open area and check your GPS accuracy there. The improved numbers will give you a better idea of how to proceed to lock down the area.

 

Third: Have your tracks turned on. Look where you have walked and see if you have crossed over where the cache has been hidden. If you have not then try and make your way to that point. Sometimes this will take you right to the cache.

 

I hope that helps :D

 

Rontro

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