Help with finding caches in the woods

[Oil Can]

I have a Garmin 76CSX and have been having a hard time locating caches that are in the the woods. All the leafs have turned and fallen so i had a clear view of the sky today with accuracy 20 feet or less. All my caches today that were in the woods were like 70 feet off from the cords posted. Is this normal? Does this come from the person that hides the cache? I seem to be right on most off the time in the city/urban areas.

I have droped my unit from about 3 feet to the black top before. Seems to be working fine but could of i messed things up? I dont have any friends that cache so i cant compare my unit with theirs. Any thoughts?

[+Miragee]

Make sure the Datum has not been changed to something other than that used for this site, WGS84. It it has been changed to NAD27 or another Datum, the location may be tens to a couple of hundred feet off, depending on where you are.

[Oil Can]

Make sure the Datum has not been changed to something other than that used for this site, WGS84. It it has been changed to NAD27 or another Datum, the location may be tens to a couple of hundred feet off, depending on where you are.

 

I just checked it and it was on WG S84. Does the GPS need to be updated with new software? I did it when i first got it in March but not since then.

[+briansnat]

You probably should update your software but I doubt that would be the reason it's off. Perhaps the hider was the one who was off. Maybe the caches where hidden with leaves on the tree and a poor signal.

[Oil Can]

You probably should update your software but I doubt that would be the reason it's off. Perhaps the hider was the one who was off. Maybe the caches where hidden with leaves on the tree and a poor signal.

 

Yea maybe your right about the hider being off. The ones today were all from the same person so it could of been a weak/poor signal at the time. The urban caches today were from different people...HHHMMMM....I never had much luck in the woods. I dont even try if its a micro AND in the woods! Thanks, I will keep that in mind.

[+Confucius' Cat]

You probably should update your software but I doubt that would be the reason it's off. Perhaps the hider was the one who was off. Maybe the caches where hidden with leaves on the tree and a poor signal.

 

Yea maybe your right about the hider being off. The ones today were all from the same person so it could of been a weak/poor signal at the time. The urban caches today were from different people...HHHMMMM....I never had much luck in the woods. I dont even try if its a micro AND in the woods! Thanks, I will keep that in mind.

You're in good company there. Micros in the woods can be very difficult even with spot-on coordinates. Unless they are hidden in a spot that just SHOUTS "cache here!" you can spend hours looking.

 

Anyway 70 feet is reasonable, but still a little high. I suspect perhaps you are finding the cache before the GPSr has had a chance to really settle down. I have found that initial readings are often as much as 100 feet off, especially if I come up on the GZ rather quickly.

 

My suggestion would be to watch carefully until you get within about 200 feet then s-l-o-w w-a-y d-o-w-n and let the machine catch up to you (I call this "letting the cache come to me" )

[GeoPirates2007]

I like that

Edited November 26, 2007 by cashking63

[Oil Can]

70 feet is good? Sometimes ground zero marks the spot and other times it could be up to 100 feet off.... Man, I guess if the hider and the cacher are both off on the accuracy you could be off alot. Slow wayyyy down might help. I was walking kinda fast. I will try that but, all those caches today were from the same guy and they were all off a bunch.

[knowschad]

Check the GPS Units and Software forum for posts on verifying accuraccy using benchmarks. I forget the details, but there are certain benchmarks that have been verified to be within inches of accuracy. There are other posts over there pertaining to GPS accuracy as well (http://forums.Groundspeak.com/GC/index.php...mp;hl=benchmark)

Edited November 26, 2007 by knowschad

[+Cardinal Red]

...My suggestion would be to watch carefully until you get within about 200 feet then s-l-o-w w-a-y d-o-w-n and let the machine catch up to you (I call this "letting the cache come to me" )

 

Confucius' Cat. Are you using a Magellan? Sure sounds like it.

 

While a Garmin can benefit from some additional time near GZ to refine the position fix, I see no reason at all to "s-l-o-w w-a-y d-o-w-n and let the machine catch up". Garmins don't have the averaging feature that Magellans do. My Garmin and I might walk away from GZ and approach again from different directions. But never at a snails pace. Any time my 76CS says the coords are 70 feet off (with good estimated accuracy), I consider those questionable coords.

[Swamp-Thing]

Just for fun try this:

 

Go back to the cache on another day and see if it still shows you are still that far off. I bet some days you are closer and some further away

[knowschad]

Just for fun try this:

 

Go back to the cache on another day and see if it still shows you are still that far off. I bet some days you are closer and some further away

 

Not neccessarily. I think its true that the day and/or time of day has some bearing, I also think that's minimal. It could be the hider that was off (due to GPS calibration or conditions that day), it could be the finder that was off (due to GPS calibration or conditions that day), or it could be the combination of each (due to GPS calibration or conditions that day). If the hider was off by 30 feet to the north, and I'm now off by 30 feet to the south... well... you can do the math.

[+edexter]

The concept of "being off" from the posted coordinates for a cache in the woods presupposes that the coordinates are "on". There are several variables that make this "impossible", chief among them being the number of satellites in view, their crossing angles and the “accuracy reading”. You will never be able to replicate any of these since they are changeable and unknown by you to begin with.

The simplest way to convince your self of this is to take a reading standing under a tree, record it, and then repeat process a half dozen times over a couple of days. Or do the same thing with two units side by side. You’ll end up with a variety of readings and “distances off” from the original coords. This is irreducible. Add in different GPSr units, varying tree cover (walk 3 feet and it changes), atmospheric differences, etc. and it’s a wonder we can find the things we do. This is why “micros in the woods” need clues to limit the search area to something reasonable.

Checking your unit against an object of known accuracy with a clear view of the sky on a cloudless day will give you some idea of the accuracy possible under conditions unrelated to actual ones and will also show the same “star burst” pattern of indicated locations as “under the tree”, just with less variation.