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Garmin eTrex accuracy


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Is it common for a GPSr to be very accurate one day and then be super waaay off the next?

 

Last weekend, our Garmin eTrex was spot-on, within 3-5 feet of the cache every time.

 

Today, it was waaaay off every single time. The first time was at least 20 feet off. The only reason I found that one is because of the clue. We even had one that was about 60-80 feet off. It also started zeroing in on one of the caches at several very different places.

 

Last weekend and today were the same type of weather (sunny) and both were in pretty dense woods, so I don't think it can be explained away by terrain or weather. The unit has not been mistreated or dropped and has been kept in a nice clean dry environment.

 

What gives?

 

I just wanted to throw it down and grind it into the mud, it made me so frustrated. We were out for at least 6 hours and only found a few caches. Some of that is probably because there is still a lot of snow on the ground though. Still, it would have helped a lot if the GPSr had performed correctly.

 

If this is uncommon, is there a way to calibrate it or fix it some other way so it will work again?

 

Thanks!

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Anyone can correct me if I'm wrong on this, but in my experience... it is Not uncommon for the GPSr's to act differently on different days even under the same weather and sky clearance conditions.

 

The Satellites that we receive the signals from are always on the move. That signal strength will no doubt add or detract from the GPSr's accuracy rating at any given time. When the satellites are lined up good, we get a good reception. If not... we don't.

 

I used to think it was all about the weather and/or tree cover overhead, but I've since been to the same location under different AND same such conditions only to find that the accuracy ratings shown on the screen are totally different compared to the last trip.

 

This is My experience, and my hypothesis on this problem. But it's only logical to me that we have to remember that the satellites may or may not be in the same position each time we use our units to get the signals.

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Geo blazer,

 

It's possible also that your GPS was dead accurate and the coordinates of the geocache were off. Using a geocache is the worst method to check accuracy. To really be sure, find a benchmark (www.geocaching.com/mark) with ADJUSTED coordinates, take your unit to that benchmark and then you can really test the accuracy of the unit.

 

Deep in the woods, any GPS unit is going to bounce around a bit.

 

Cheers.

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Geo blazer,

 

It's possible also that your GPS was dead accurate and the coordinates of the geocache were off. Using a geocache is the worst method to check accuracy. To really be sure, find a benchmark (www.geocaching.com/mark) with ADJUSTED coordinates, take your unit to that benchmark and then you can really test the accuracy of the unit.

 

Deep in the woods, any GPS unit is going to bounce around a bit.

 

Cheers.

Sun spots....

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I have found that one day my Dakota 20 can be super accurate and on another day it seems to be out.

 

I believe that it has to do with the number of satellites the GPSr can see. Some days there seems to be lots and some days there seems to be a lot fewer.

 

But having said that...the GPSr seems to be as accurate, just the error number calculated is larger.

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I have found that one day my Dakota 20 can be super accurate and on another day it seems to be out.

 

I believe that it has to do with the number of satellites the GPSr can see. Some days there seems to be lots and some days there seems to be a lot fewer.

 

But having said that...the GPSr seems to be as accurate, just the error number calculated is larger.

 

Check this out and see if your errors correspond to poor visibility times. You can scroll the chart backwards and forward by a day at a time to see what was or will be the constellation.

 

http://www.navcomtech.com/Support/Tools/sa...dictor/main.cfm

Edited by guggie
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Today, it was waaaay off every single time. The first time was at least 20 feet off.

 

20 feet is not waaaay off. It's not even a little bit off. It's well within the expected margin of error for a handheld GPS.

 

I was comparing it to last weekend, when the GPSr was within 3-5 feet of each of the caches we found. Every one of them. To me, after that, 20 feet IS waaaay off, no matter what the accepted margin of error is LOL.

 

We are very new at this and still trying to figure it all out. I was bitterly disappointed in the performance of the Garmin after (apparently) being spoiled by it last weekend. Hubby wasn't nearly as upset as I was. His guess was as some of you have said, that it had something to do with the satellites.

 

I'm the one who wanted to get into this game and waited for about 2 years before we acquired a GPSr, not hubby. That's probably why I'm so upset that it appears to not be working properly.

 

I actually feel a lot better today, after reading the responses to my question, than I did last night. I was afraid that after waiting for a couple of years for a GPSr that we got a dud, and wondering how long it would be before we could get another.

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Today, it was waaaay off every single time. The first time was at least 20 feet off.

 

20 feet is not waaaay off. It's not even a little bit off. It's well within the expected margin of error for a handheld GPS.

 

I was comparing it to last weekend, when the GPSr was within 3-5 feet of each of the caches we found. Every one of them. To me, after that, 20 feet IS waaaay off, no matter what the accepted margin of error is LOL.

 

We are very new at this and still trying to figure it all out. I was bitterly disappointed in the performance of the Garmin after (apparently) being spoiled by it last weekend. Hubby wasn't nearly as upset as I was. His guess was as some of you have said, that it had something to do with the satellites.

 

I'm the one who wanted to get into this game and waited for about 2 years before we acquired a GPSr, not hubby. That's probably why I'm so upset that it appears to not be working properly.

 

I actually feel a lot better today, after reading the responses to my question, than I did last night. I was afraid that after waiting for a couple of years for a GPSr that we got a dud, and wondering how long it would be before we could get another.

 

You don't seem to have a dud. The stars (or should I say sats) all aligned your first time out.

 

You have to remember that even if you had a $5,000 GPS with pinpoint accuracy, the unit used by the hider still has a margin of error of about 10-30 feet. Since your unit has a similar margin of error caches will rarely be where your GPS says it is. In fact when your GPS was 22 feet off it is possible that YOUR GPS was correct and the hider's was off. Usually units of both the hider and searcher are off some, so caches are regularly found 20, 30, 40 feet or more from where your GPS says it should be.

 

I'd say 80 percent of the time you will find the cache under 30 feet off, but even 60+ feet is not unheard of in areas with signal difficulties.

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Today, it was waaaay off every single time. The first time was at least 20 feet off.

 

20 feet is not waaaay off. It's not even a little bit off. It's well within the expected margin of error for a handheld GPS.

 

I was comparing it to last weekend, when the GPSr was within 3-5 feet of each of the caches we found. Every one of them. To me, after that, 20 feet IS waaaay off, no matter what the accepted margin of error is LOL.

 

We are very new at this and still trying to figure it all out. I was bitterly disappointed in the performance of the Garmin after (apparently) being spoiled by it last weekend. Hubby wasn't nearly as upset as I was. His guess was as some of you have said, that it had something to do with the satellites.

 

I'm the one who wanted to get into this game and waited for about 2 years before we acquired a GPSr, not hubby. That's probably why I'm so upset that it appears to not be working properly.

 

I actually feel a lot better today, after reading the responses to my question, than I did last night. I was afraid that after waiting for a couple of years for a GPSr that we got a dud, and wondering how long it would be before we could get another.

 

You don't seem to have a dud. The stars (or should I say sats) all aligned your first time out.

 

You have to remember that even if you had a $5,000 GPS with pinpoint accuracy, the unit used by the hider still has a margin of error of about 10-30 feet. Since your unit has a similar margin of error caches will rarely be where your GPS says it is. In fact when your GPS was 22 feet off it is possible that YOUR GPS was correct and the hider's was off. Usually units of both the hider and searcher are off some, so caches are regularly found 20, 30, 40 feet or more from where your GPS says it should be.

 

I'd say 80 percent of the time you will find the cache under 30 feet off, but even 60+ feet is not unheard of in areas with signal difficulties.

 

Got it! Thanks!

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As others have suggested, your unit appears to be operating correctly. The standard error for recreational grade gpsr is more than 20ft. And, if you take into account that the person who hid the cache also has a unit that is limited by that standard error, you could be off by 40 ft and still not question the accuracy of your gpsr.

 

If you are concerned about the accuracy of your gpsr, trying looking for a few benchmarks - preferrably benchmarks in open places, with a clear view of the sky. I suspect that, for most of them, the gpsr will read well within its published standard error. But, don't expect that level of accuracy when you are searching for caches.

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Like someone else stated, you can't tell anything about the accuracy of a gps by geocaching. There is more to geocaching than using a gps to find the exact coordinates.

 

Mark some stuff around your house, see how close it comes day after day.

 

Also like someone said, you aren't going to get pinpoint accuracy. Just so you aren't shocked - the odometer may be off some as well.

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I've got an eTrex Vista CX, and have the same issue. Some days it seems to pinpoint caches really well. On other days, it consistently places ground zero about 20-30 feet East of where it actually is. Weather and other conditions don't seem to be a factor in whether it's a "good" day or an "off" day. On "off" days, we just find the supposed gz, then turn on the geosenses and start searching 20-30 feet West of that. But that first cache of the day, when figuring out what the receiver is gonna do, can be a pain! I know that 20 feet is in acceptable error range, and all that other jazz that goes along with geocaching, but I find it strange that when it seems to be drifting, it's always drifting to the East.

 

We're going to be placing our first geocache this morning. It'll be REALLY interesting to see if the coordinates we come up with are fairly accurate or not.

Edited by Triskeles
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We're going to be placing our first geocache this morning. It'll be REALLY interesting to see if the coordinates we come up with are fairly accurate or not.

As I'm sure you've seen emphasized elsewhere, be sure you use your Vista to AVERAGE for a minute or two when you mark the point for your new cache. In fact, turn it on, wait until the 'radius' in feet settles to what you would normally call a 'good' level, and THEN do the waypoint marking using the unit's averaging feature.
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