Garmin "MARK" 0.34 miles off.

Were you under dense canopy or in an area that could have affected the signal strength (like at the bottom of a cliff or in a canyon with steep sides)?

I have an Oregon, so I am not familiar with the features of the eTrex. My Oregon displays an estimated "GPS accuracy". Does the eTrex have something similar? It does seem like .34 miles is a large error tho.

Thanks for asking.

No. It was not in a canyon, etcetera, and had few trees at that spot, with a clear line of sight to the satellites. I waited on powering up to ensure it was reading all satellites before marking.

Even so, the eTrex is a phenom in heavy woods – I can even get full coverage in my home office.

It’s just out-of-the-park weird to have it MARK something so far off. When I returned to the pickup, I marked it, again, and it was then correct, and confirming my “0.34 mile off” distance. I thought at first it may be a software problem but dismissed that from what I read on the Garmin Website.

It’s a head scratcher.

3/4 mile really is unusual. My Magellan hand-held has always been accurate to just a few feet, similar to your etrex. Here is a screen shot from my 1490 while sitting in the driveway for a few hours, with a clear view of the sky.
http://i139.photobucket.com/albums/q297/spokybob/1218088May1...
It is possible that it was off by 3/4 mile that day.

spokybob, .34 miles is actually closer to 1/3, not 3/4 ... about 1800 feet. But I agree that is a large error.

I have had my Oregon be off by two or three hundred feet in certain circumstances, but not that much. Unless it happens again, I guess I would chalk it up to an unusual satellite constellation that corrected itself by the time you got back and took another mark.

Just out of curiosity, was the incorrect waypoint on or near the track you hiked while hunting? Or was it completely off in a different direction?

Looking at my screen shot, the error was more than .34 at least 4 times that day.

Good questions, and hey you guys aren't so bad.

The 0.34 bad location was not along a waypoint. It was NE in a position I had not been, before.

I had not heard this possibility, "unusual satellite constellation that corrected itself " before . . . I would not think that possible in the WAAS mode, or is that fairly common?

Whoa! And, I read spokybob had this happen 4x in one day! So this may be common?

Thanks, by the way, for the welcome.

I am still trying to figure out who said what, when, how . . .

Usually when you see drift and track scatter when standing still, like spokybob demonstrated in is screenshot, you will also see your current speed fluctuate even tho you are standing still. It is pretty common, especially in the first few minutes after you boot up a gps and it obtains a lock. It only takes 3 or 4 satellites to get the lock, then the accuracy gradually improves are more satellites lock in and correct each other. And the constellation can make a difference. Certain patterns triangulate more accurately with fewer satellites. For example if the first 3 or 4 locked in are somewhat linear with your location, the error wil be greater. But even with that, I think a 1800 foot error is pretty unusual.

THAT makes sense. Thank you.

Yes. It seemed unusual to me, too. The eTrex has been unerringly accurate last three years, so it was a, "What the H___?" moment. Especially as I was in back country, circled by trees within arm's reach, and finding my way out could have meant hours of walking.

Close to boot with "four locked to start" (mine starts at four) but linear satellites . . . that also explains the early on diminished accuracy until it gets going a while.

This was very fun to read, and I appreciate the time and explanation alandb and others' input. This could be very helpful.

Tom Smith

a waypoint averaging function like my Oregon? I sometimes use waypoint averaging when placing a new geocache so I can publish coordinates as accurate as possible. One of the interesting things I have observed is that sometimes I can let the averaging go for a long time ... 8 or 9 minutes and it cannot get up to more than a 70% to 80% confidence. I can then go back to the same spot the next day and the averaging will go up to 100% confidence in just a couple of minutes. I don't know why this is, but I always suspected that it has something to do with how optimal the constellation pattern is for my location at the given point in time. That is just a guess on my part ... don't really know that much about it.

I tried geocaching one day a few years ago. I wondered if the person that placed them had the same model gps as I. When I arrived at the lat/long, everyone of them were less than 10 feet away. I thought it was too easy.

and it is still hard to find. You must have picked easy ones ... with a difficulty level of 1.

I did not know there was levels of difficulty. I found all of them in my county.

There is no waypoint averaging function on this eTrex, although I think it's their basic model from 2009. That's informative on the readings you're getting.

Each cache has a difficulty rating from 1 to 5 in increments of 1/2, 1 being easiest, 5 hardest. This is an indication of how difficult the cache is to find or retrieve once you are at or near the cache's ground zero location. Some caches also are puzzles that you have to solve in order to get the true coordinates where the cache is located. So in those cases the difficulty rating could indicate the difficulty of solving the puzzle.

Each cache also has a terrain rating on the same scale which is an indication of how hard of a time you will have getting to ground zero in the first place.

Here is Garmin's Customer Service response via E-mail, last night about 9:30 PDT:
“Thank you for contacting Garmin International.
It is most likely due to environmental interference, or it had only just acquired 3-4 satellites and still did not have a very accurate location yet.
Please answer some questions for me. Did you park your vehicle next to any buildings or structures? Were there power lines nearby? How many satellites had you acquired before marking your location?
Also, does the unit say 12 Channel GPS or High Sensitivity Receiver on the faceplate?
Feel free to respond with any further questions. [bold added]”

My reply is as follows:

"Thank you for following up.

• My Garmin eTrex does say “HIGH SENSITIVITY” on the faceplate.
• I was not near a large building or power lines.
• I was in a wooded area, but mostly clear where I marked the location.
• I just powered up and waited for the image to show four satellites tracked by the eTrex
o Although I now see it says 'ready to navigate' after three are tracked, so it could have been three when I marked location."

It was three days from my enquiry to their first response. So far, alandb, their answer is similar to yours, locating/marking shortly after powering up is not very accurate and environmental interference may also come into play.

Sunspots!

You may have accidentally activated the "Forced Exercise" feature.

Welcome to the POI Factory.

LOL! That gave me a chuckle.

Garmin is merciless! (I was carrying around a 50lb., no wonder they don't advertise that feature.)

Thanks.

LOL! That gave me a chuckle.

Garmin is merciless! (I was carrying around a 50lb. salt block. No wonder they don't advertise that feature.)

Thank you for the laugh and welcome.

As a follow up, I should include what looks like Garmin’s last reply.

Marking a location with time between and after boot up might be handy failsafe practices.

I sent but don't know why (they've not replied) the serial number was important except for maybe their tracking purposes.