GPS keeps changing it's mind

[+Rckhnd]

Not being real familiar with using a GPS, I get mixed signals from my Garmin.

It will tell me (for example) the cache is 20' south. When I move 20 feet south, it now says 15' east. This can go on for quite a while and only once did I get a 0' reading implying I was right on top of it.

 

What is the standard for accuracy with these devices? Granted +/- 20 feet is no problem for finding my truck or campsite, but for hunting a microcache, it can be a problem. I spent an hour yesterday trying to pinpoint a microcache and now it's turning into an obsession with me to find this little bugger.

 

Is there any way I can improve the performance of my Garmin e-trex legend H?

[+kunarion]

When I move 20 feet south, it now says 15' east.

That's perfectly normal operation. The GPSr is constantly averaging signals, and is affected by slight reception changes caused by nearby obstructions.

 

Once you're at the spot (plus or minus say 30 feet), you're there. Put away the GPS, now it's time to search. Use the hint, the description, and your Geosense, and hunt down that evil little Micro. Look for hiding spots, then look in and on those hiding spots.

 

I have had some luck walking a few yards from GZ, and checking the angle and distance, then walking to some other spot to "triangulate" it.

Edited December 5, 2010 by kunarion

[+Driddy]

The problems you are describing are often due to terrain. I urban areas this can happen around tall buildings and in the woods this often happens along steep hillsides or in canyons. I believe the issue is that under these conditions you may have a pretty poor satellite configuration (access to some sats may be obscured). I am sure others (particulary in the Technology forum) could provide a much deeper explanation.

 

What I can tell you is that you will learn techniques for dealing with this as you become more experienced. A few observations/suggestions:

 

1) If you can't get to 0-1 feet, then you may not be a the true ground zero. "Phantom" GZs sometimes show up and the real GZ may be some distance away (but usually within maybe 30 feet of the phantoms). This is my observation and I can't scientifically support this.

 

2) When you get close to the apparent GZ, slow down or stop or you might walk past GZ. I sometimes find that my GPSr is slow to update its position display when sat reception is sketchy. Also, standing still for a few moments sometimes seems to let the unit get a better fix on location.

 

3) Probably the most useful advice I have to offer is to learn to triangulate. Move a substantial distance away from the vicinity of GZ -- perhaps 100 feet (ideally to high ground or an open space) and note where your GPSr is pointing. Then do this a few more times from other angles relative to GZ. Where do the imaginary lines intersect? That spot is likely GZ. An abbreviated version would be to do this from a single spot where you have reason to believe you can get a decent reading and then search near the spot indicated from a distance.

 

4) Combine any of the above with your "geosense" (knowledge of where caches are typically hidden) and the difficulty rating and focus your searching on where the cache is likely to be.

 

5) Set up a search grid with margins extending beyond where you think GZ and then very systematically search the grid. Repeat if there seems to be more than one candidate for GZ.

 

6) Look for "geotrails" left by other cachers if the cache has been recently found. I have noticed that I have been slowly learning to track as I gain experience as a geocacher.

[+kini_ont]

All good answers but as I see your a newcomer (Welcome) and have yet to get your geo senses activated, so my recommendation to you would be to start with larger caches (easier to find) and through in the smaller ones with no expectations or disappointment, These advice was given to me when I started and I`ve stuck with the game you`ll catch on don`t worry.

As for the gps, I think eveyone starting fells it should zero out at GZ but you have to remember your gps may have an accuracy of 12-15 ft and the cacher who placed the cache has the same accuracy , well you can see why you sometimes need to search it out. Personally I like, from there it is more search th to stop about 30-40 ft out and see where the gps is pointing me, from there it is more search to find then finding GZ to search

Have fun and enjoy

[+Rckhnd]

Thanks for the replies and tips!

 

Triangulation does seem to be the answer here. I'm fairly good at tracking animals, but never considered tracking a human!

 

If the accepted margin of error is as you have indicated, then it does add a little more gratification when the cache is found...

 

Thx all!

Rckhnd

[+michigansnorkelers]

It is normal for coordinates to drift. Position is always approximate.

 

Here is a quick learning exercise:

 

Go in you backyard and set your GPSr in a place with good reception, where it won't be disturbed. Now, turn on tracking and walk away for fifteen minutes. When you come back, carefully turn off the tracking and save the track.

 

If you look at the track, it will appear that the GPSr had been wandering around, like a dog on a leash. Of course, it was stationary. It was the GPSr coordinates that wandered.

[+Huntleigh]

...snip the good stuff...

2) When you get close to the apparent GZ, slow down or stop or you might walk past GZ. I sometimes find that my GPSr is slow to update its position display when sat reception is sketchy. Also, standing still for a few moments sometimes seems to let the unit get a better fix on location.

... more snip...

 

I'd dispute that. I've found with my Venture (a cousin of the Legend) that when using the compass rose to find the cache the unit needs to be moving. The distance to GZ might be accurate but the direction arrow may be pointing in the opposite direction if you are stopped.

[+NYPaddleCacher]

The problems you are describing are often due to terrain. I urban areas this can happen around tall buildings and in the woods this often happens along steep hillsides or in canyons. I believe the issue is that under these conditions you may have a pretty poor satellite configuration (access to some sats may be obscured). I am sure others (particulary in the Technology forum) could provide a much deeper explanation.

 

What I can tell you is that you will learn techniques for dealing with this as you become more experienced. A few observations/suggestions:

 

1) If you can't get to 0-1 feet, then you may not be a the true ground zero. "Phantom" GZs sometimes show up and the real GZ may be some distance away (but usually within maybe 30 feet of the phantoms). This is my observation and I can't scientifically support this.

 

2) When you get close to the apparent GZ, slow down or stop or you might walk past GZ. I sometimes find that my GPSr is slow to update its position display when sat reception is sketchy. Also, standing still for a few moments sometimes seems to let the unit get a better fix on location.

 

3) Probably the most useful advice I have to offer is to learn to triangulate. Move a substantial distance away from the vicinity of GZ -- perhaps 100 feet (ideally to high ground or an open space) and note where your GPSr is pointing. Then do this a few more times from other angles relative to GZ. Where do the imaginary lines intersect? That spot is likely GZ. An abbreviated version would be to do this from a single spot where you have reason to believe you can get a decent reading and then search near the spot indicated from a distance.

 

Remeber, the object of this game is not to see how close you can get to Ground Zero (the coordinates the the cache owner published for the cache). The object is to find a geocache.

 

Consider that the coordinates that the the cache owner published were taken using a GPS that is only accurate to 15 or so feet and that it's not uncommon to be further off than that.

 

You can spend 15 minutes triangulating from three different directions and *maybe* get to the same coordinates that the cache owner published but you still might be 20-25' from a large stump in the ground where the cache is actually hidden.

 

One of the best methods that I have used basically works like this. When I get to within 100' (and sometimes more if I'm in open terrain) I look in the direction that the arrow is pointing and estimate a spot 100' in the distance and see if there is anything that might be a potential hiding spot. It could be a tree stump, some unusual object, or anything that stands out in the area. I basically think, if I were to hide a cache in that direction, where would I put it. Then I head directly for that object and look for the cache. If the area doesn't have much open terrain I still try to identify "something" while I'm further away from GZ that will give me a place to start my search. Knowing the name of the cache and having read the description and, optionally, the hint, can narrow down the areas I'm going to focus on first. The only time this doesn't work real well and I have to try to rely on my GPS more is when there are a gazillion possible hiding places.

[+Driddy]

...snip the good stuff...

2) When you get close to the apparent GZ, slow down or stop or you might walk past GZ. I sometimes find that my GPSr is slow to update its position display when sat reception is sketchy. Also, standing still for a few moments sometimes seems to let the unit get a better fix on location.

... more snip...

 

I'd dispute that. I've found with my Venture (a cousin of the Legend) that when using the compass rose to find the cache the unit needs to be moving. The distance to GZ might be accurate but the direction arrow may be pointing in the opposite direction if you are stopped.

 

I wasn't referring to the bearing indicator (but I agree that your point is valid for units lacking an electronic compass). I was referring to the unit's location fix and I am not aware of any units that give a more accurate location fix when they are moving.

Edited December 5, 2010 by Geo Peeps

[+LukeTrocity]

Once you hit within 10-20 feet, put down the GPS and open your eyes. That's the best advice I can give you, that's what works for me!

[+kunarion]

I spent an hour yesterday trying to pinpoint a microcache and now it's turning into an obsession with me to find this little bugger.

That's what's fun about Micros. You may be within feet of it, and still have many hours of "fun" searching, head-scratching, trying various tools (mirrors, magnets, even a couple gallons of water in some cases). A Micro may be a challenging puzzle, and the container may be the size of your fingertip, and camouflaged to match the hide site. It can be practically anything, and if you're real lucky, it will be something not quite right, which you'll notice if you step back and just look. If the description doesn't narrow it down, the Cache Owner probably intends it to a be tough one. Take them up on the challenge or go for an easier cache instead, it's up to you.

 

But once you're close enough to decide which park bench (for example) to try, the GPSr has done all it can.

Edited December 5, 2010 by kunarion

[+GeePa]

The One I think you are trying to find looks like a difficulty three which means it is supposed to be hard to find (even if you are standing next to it). If I have the correct one then you may want to consider working out the hint. I did, and it sounds helpful.

 

Like others have said, it may be better to keep this one in mind for later after you have found a few and have a better sense for how some of these things are hidden.

 

Good luck

[+msrubble]

It will tell me (for example) the cache is 20' south. When I move 20 feet south, it now says 15' east. This can go on for quite a while and only once did I get a 0' reading implying I was right on top of it.

 

Completely normal, once you get that close to the cache.

 

One thing that might help you pin down ground zero is, if you are using the compass-like view, switch to the map page. Instead of wondering which way is north-northeast, you can say, "Oh, it's pointing to my left." Or sometimes you can walk in a circle around ground zero, so you know where to start your search.

[+BlueDeuce]

...snip the good stuff...

2) When you get close to the apparent GZ, slow down or stop or you might walk past GZ. I sometimes find that my GPSr is slow to update its position display when sat reception is sketchy. Also, standing still for a few moments sometimes seems to let the unit get a better fix on location.

... more snip...

 

I'd dispute that. I've found with my Venture (a cousin of the Legend) that when using the compass rose to find the cache the unit needs to be moving. The distance to GZ might be accurate but the direction arrow may be pointing in the opposite direction if you are stopped.

 

Standing still is only helpful when trying to get a Sat lock under open sky. Even if you have a compass-enabled gps, you have to be in motion so that the gps knows which way to point you.

[+dfx]

another reason why this is happening to you can be either the electronic compass of your GPSr needing a recalibration if it has one, or if it doesn't have one you not being aware of that fact.

 

in other words: if your GPSr has an electronic compass, you may need to recalibrate it. and if it doesn't, you need to be aware that when you're standing still, the arrow will be mostly useless and will not really point to GZ.

Edited December 6, 2010 by dfx

[+Ed56]

Welcome to Geocaching! I've run into exactly the problem (chasing my tail) you've described many times and have a a technique for getting around it that works pretty well for me. Once I'm within roughly 70 feet of where my GPSr says the cache is hidden I get out my compass and start following the bearing indicated by my GPSr.

 

The compass I use is one that can be adjusted for magnetic declination so that the needle points to "true north" which is what your GPS receiver is based on. Suunto MC-1, Silva Ranger and other compasses have this adjustable declination feature.

 

If I don't find the cache along the first bearing line I back off to another location and approach again. This is similar to the triangulation method someone mentioned earlier. An adjustable declination compass will cost about $45 to $50US which is more than some folks want to pay. But I've used the heck out of mine and it was a good investment.

 

You can look up the magnetic declination for your area on line at the NOAA site or elsewhere. Sorry for the long-winded response but I hope this helps. Happy hunting, Ed56

Edited January 16, 2011 by Ed56

[+humboldt flier]

Psssssssst.

 

Your machine is not giving you mixed signals ... It is teaching you the first four steps in the " Drunken Geocachers Dance "

[+StarBrand]

The general accuracy of most handheld GPS devices is around 15 to 25 feet. Remember though you have might have to add your potential error to any error the cache owner had when placing the cache. That means you could easily find yourself looking for a cache up to 50 feet from where your unit says ground zero is. Most of the time you will find them within 20 feet or less but do be prepared to widen your search. Put the GPS away when you are within 20 feet or so and start looking for likely hiding spots.

 

Back off and re-approach the area if necessary to verify you are looking in the right spot. Also remember that signal strength and the geometry of the sats is constantly changing overhead.

[+popokiiti]

I see you found it! Well done and welcome to the game!