GPS and moderate/heavy tree cover

[+Picup Andropov]

We've set up a micro in the area and are having some difficulty with getting the GPS to agree on a solid set of coordinates. The tree cover seems to be playing havoc with the GPS. Any thoughts/angles/solutions? Thanks!

[+PeterNoG]

No solution, but remember that finders will have the same problem. A micro in the forest with poor coordinates usually requires a good hint if you want happy sucessful searchers.

[+Iowa Tom]

This may not help if your unit cannot average for an extended period of time. I myself always mount my GPS unit on a stand then let it average for 10 minutes, at least. On one cache that is a little ways into the woods I provide a coord outside the woods then say “walk straight east 20 feet to the cache.”

 

-it

Edited April 8, 2007 by Iowa Tom

[+LennyTheLizard]

This may not help if your unit cannot average for an extended period of time. I myself always mount my GPS unit on a stand then let it average for 10 minutes, at least. On one cache that is a little ways into the woods I provide a coord outside the woods then say “walk straight east 20 feet to the cache.”

 

-it

I've only hidden a couple caches, and my method is a little crude. I just stand right at the cache and mark a waypoint. Walk away from the cache about 10-15 yards, then walk back to it and mark another point. Walk a different direction each time (5-10 times). Then at home just use a calculator to average all your points. That should get you pretty close.

[Neos2]

This may not help if your unit cannot average for an extended period of time. I myself always mount my GPS unit on a stand then let it average for 10 minutes, at least. On one cache that is a little ways into the woods I provide a coord outside the woods then say “walk straight east 20 feet to the cache.”

 

-it

I've only hidden a couple caches, and my method is a little crude. I just stand right at the cache and mark a waypoint. Walk away from the cache about 10-15 yards, then walk back to it and mark another point. Walk a different direction each time (5-10 times). Then at home just use a calculator to average all your points. That should get you pretty close.

That "crude method" that Lenny mentions really works. We did this when we were using our Legends to create new caches--only we walked a bit furhter away than that, say 30 feet or so. We'd do that with both of our units five times and average the ten readings. Usually, we'd see one set of cords show up over and over again while we were taking the readings. If not, we'd double the number of readings.

 

We got lots of nice logs to the cache page saying the good cords helped make it an easier find than it could have been.

[+uxorious]

I use the same "crude" method Lenny uses. Works good for me most of the time.

 

only we walked a bit furhter away than that, say 30 feet or so.

 

Not to get too picky, but Lenny said he walks 10 to 15 YARDS, which is 30 feet or so. (30 to 45 feet actually)

[Suscrofa]

I use the same "crude" method Lenny uses. Works good for me most of the time.

 

only we walked a bit furhter away than that, say 30 feet or so.

 

Not to get too picky, but Lenny said he walks 10 to 15 YARDS, which is 30 feet or so. (30 to 45 feet actually)

Amusing isn't ? A fun we miss, we metric users !

[+ImperfectSense]

How can you tell if your unit averages over time? I haven't really seen that listed on the "Features" pages at any manufacturer sites... for example, I've got an eXplorist 400, no idea if it averages or not...

[+LeonW]

Have to agree with Suscrofa, I missed that one totally as I am also metric. All I do is to average the co-ords. by pushing the button on the Garmin 60CSX for a count of 40 measurements, faster than I drink a refreshment.

 

The idea to take an accurate measurement and combining that with a reasonable small amount of compass work has really caught my interest. It would make finding spot X, just that more realistic. But I fear that this practice might be under another adventure game. Mind that I am talking of say moving 8 meters east to the front of a big rock, followed by 9 meters north, between two boulders, and another 6 meters North-east, through the rows of pines to spot X. What would be your opinion be on such a hunt.

 

LeonW

 

[+Iowa Tom]

I used to take a reading at the cache then walk off in a different direction 8 times, wait until my unit began to average, then move back to the cache and take a reading once it began to average. I finished by hand averaging all of those readings back home. That was quite a hassle and came to the conclusion that maybe just letting it sit and average once a second, or whatever it is, for 10 minutes, would do the same thing with a lot less work. I rarely get complaints about the accuracy of my readings done either way, and I own a lot of caches.

 

Likewise the visitor should get close to the right spot, wait for their unit to average for a minute, look to see which direction and how far to move, move there and wait a minute again if necessary.

 

I use Magellan and don’t remember if a Garmin averages automatically or not.

-it

[+Renegade Knight]

I just let the GPS sit and average the location while I hide the cache and perfect the camo etc.

[Neos2]

Yikes! I did see yards and read it as feet. Good catch. We all had the same idea, walk away to a point where someone might approach the cache and move toward the cache to allow the GPS to finds coordinates to the right spot.

 

We use a 60CSx, a 60CS, or a 76CS nowdays, and let them do the averaging. We still take a couple of independent marks on the spot just to see how well they match up to the average.

 

The average can still be off by a good distance, depending on all sorts of factors. And the next person's GPS may be more accurate, or less accurate than your GPS and conditions could just be lousy for either of you on either day.

 

It's all part of the process. No GPS is soooo accurate that it will take you to the top of the cache every time, and ya know, that's more than OK by most of us, since we do enjoy the hunt --but we do want to at least be in the same field as the cache, so we appreciate those of you that try to come up with good cords.

[Suscrofa]

I feel that we gain accuracy by averaging values taken at different days.

[+Iowa Tom]

I feel that we gain accuracy by averaging values taken at different days.

That is true based on what I have read in articles that were quite detailed about the subject.

 

The error is compounded by the fact that the second person's unit is imperfect and conditions are different for them when they arrive. It’s error upon error so your initial reading is bound to be better than the next person’s. What I don't care for is the drop-n-click method used by some people that really don't know (or care) how to get a reasonably accurate coord of their cache when they leave it.

 

Until recently I didn't realize that professional systems also have trouble with tree cover as well. They too have to let their unit sit for quite some time to get super accurate data.

-it

[+miles58]

Go buy an external antenna with a five meter cable. beg borrow or steal some velcro cable ties. Velcro the external antenna onto a long stick and hoist it as high as you can while you take an averaged reading. Be sure to have a ground plane to use with the antenna even though it will still work without one. The external antenna alone will make a big difference. Add a ground plane and it gets better. Hoist it up fifteen feet and it makes the most difference. Do all three at the same time and you can get good numbers in almost any woods.

[+briansnat]

If you can get a better signal lock 10-20 feet away than you can right at the cache you are better off taking your reading away from the cache a bit A good reading a little off is better than a lousy one at the cache site. I have had to do this for several caches I've hidden and have received no complaints about the coordinates.

 

As far as averaging suggested by many, if you are getting a lousy signal you will just be averaging bad data.

 

One option is to create an offset. Have the GPS take the searcher to an easily identifiable object like a unique boulder, lone tree, sign, etc... where you can get a good reading. Then have the the searcher walk X paces at yyy degrees.

[dsandbro]

External antennas significantly improve accuracy, even if you cannot get the antenna above the obstructions.

 

I attach the antenna to the top of my hiking stick and just let it stabilize and auto-average.

[+Iowa Tom]

Are the external antennas only available for Garmins?

[+Knight2000]

No solution, but remember that finders will have the same problem. A micro in the forest with poor coordinates usually requires a good hint if you want happy sucessful searchers.

 

Just be reasonable and do not make it a hint like this!

 

What about people passing through on vacation? Or those that will never be back?!

[+briansnat]

We've set up a micro in the area and are having some difficulty with getting the GPS to agree on a solid set of coordinates. The tree cover seems to be playing havoc with the GPS. Any thoughts/angles/solutions? Thanks!

 

Exactly how far apart are the various coordinates? Not being able to get solid coordinates is quite normal.

I can sit any of my units (Garmin and Magellan) on a treeless mountain top with sunny skies and watch the numbers fluctuate all day.

 

If you're talking a matter of 10-20 feet don't even give it a moment's thought. Mark and post.

[+TrailGators]

Every six feet is 0.001 minute so you can pace S or E to a clearning in increments of six feet and add your offset to determine the cache coords (if you go north or west you need to subract). For example, if you go to a clearning that is 30 feet south of the cache then add 0.005 to those coords. This works very well for me.

[+Iowa Tom]

Every six feet is 0.001 minute

Technically, the distance for 0.001 minute longitude is not the same as 0.001 minute latitude. Longitude converges as we move from the equator but latitude does not. I don't know that I would worry about the difference though.

[+TrailGators]

Every six feet is 0.001 minute

Technically, the distance for 0.001 minute longitude is not the same as 0.001 minute latitude. Longitude converges as we move from the equator but latitude does not. I don't know that I would worry about the difference though.

This is true. If you live closer to the poles you would have to add a smaller number for E-W adjustments. But this method should work for the vast majority of folks around the globe.