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eTrex10 Inaccurate Distance Measurements

Not knowing a lot about GPS, I bought a Garmin eTrex10 to keep track of how far we have walked while hiking. I'm not interested in creating waypoints or routes, or anything like that. I just wanted something to track mileage, essentially like a pedometer, but something that would work on uneven ground with varying paces. The "Trip Computer" on the eTrex 10 is basically what I was looking for.

Unfortunately, the trip distance on the eTrex 10 is often way off when we are hiking, usually over estimating the distance. For example, on a recent 5 mile hike it said we had hiked 6.3 miles. That's not real helpful when we're out on a trail and want to know how much farther we have to go, especially when we're hiking an unplanned trail.

I tested the GPS at our local park that has trail markings every quarter mile. It was spot on, but I was walking non-stop from start to finish. Our signal always seems to be good while hiking, so the inaccuracy seems to be caused when we are standing still. Stopping to take pictures, to eat lunch, or even just to catch our breath while climbing a hill. I know here at home the eTrex10 will rack up distance even when it's sitting in one spot on my desk. It records movement even though we are standing still.

I don't see a way to pause the etrex 10 GPS, so I'm guessing there is nothing I can do about it.

However, I'm curious if there are better handheld GPS units that have some kind of motion sensing (accelerometer or something) that won't record movement when we are sitting still? Handheld or watch style.

Comments

  • sussamb 813 Points
    If I stop for any length of time I switch my Etrex 20 off. That way my distances are pretty much accurate.
  • DaveM 159 Points
    When you get to the trail head or before power up your GPS and let it get a good lock on the satellites before resting the trip computer. If it doesn't have a good lock it can add mileage.

    If you don't have GLONASS enabled I would enable it. With GLONASS enabled if you are in an area with poor satellite signals do to trees etc. it will have more satellites to work with. With the better signal it won't bonce around as much when you stop.
  • privet01 215 Points
    edited October 2015
    If you upload the track information for one of the activities where you had a distance discrepancy to google earth, garmin basecamp or other such application, you can zoom in all the way on the start of your track where you initialized it and also places where you stopped for a while without turning off the gps. Then you'll see how much "wandering" around a gps will do. It may help you understand why the above to posts are recomended SOP.

    The gps has no way of knowing when you are really stationary.
  • Boyd 1985 Points
    edited October 2015
    I did some testing of this awhile back in conjunction with my review of the Garmin GLO at GPSTracklog. In each of these charts, the GPS recorded one point per second while sitting stationary at the center of the "bullyseye" for half an hour. The rings of the bullyseye are spaced one meter apart. It's remarkable how much they wander.

    Here is the GPSMap 60csx.

    image


    And the Montana 600

    image
  • The gps has no way of knowing when you are really stationary.
    That's why I was wondering if anyone made a GPS with an accelerometer or foot pod of some sort that could sense when I'm actually in motion. Essentially pause the GPS pings until I start moving.

    If I can remember, I will try turning off the eTrex 10 when we stop for lunch or something more than a few minutes. I always wait for a full signal lock before clearing the track and data settings.
  • privet01 215 Points
    edited October 2015
    The Garmin Fenix has a feature to pause track recording, which is intended for situations like yours. Also the Garmin Forerunner's and Edge, which are intended for running and cycling respectively, use a timer and do not record data when you stop the timer. Some have maps, but use a very small display. Others don't have maps, but if you are more interested in the data after you've returned from your activity, then they might be the thing.

    Of the Fenix, Forerunner and Edge...... the Fenix models are intended for hikers, the Forunners for runners and the Edge's for cyclists. Unless you also bicycle, then I'd opt for the Forerunner if the Fenix is too pricey. Though I've used my Garmin Edge 500 for some walks with reasonable results, it's features and programming are tuned exclusively with cycling in mind as are all the other Edges.

    It seems as if I have heard or seen that some of the Garmin handhelds have a feature to easily pause the track recording too, but none come to mind at the moment.
  • Boyd 1985 Points
    privet01 said:

    It seems as if I have heard or seen that some of the Garmin handhelds have a feature to easily pause the track recording too, but none come to mind at the moment.

    IIRC, this feature was introduced with the Oregon 600 series. I think all handheld models released since then also have the pause feature. Not sure about the eTrex series though, since it's their entry level handheld and Garmin is infamous for deliberately leaving features out of less expensive devices. ;)

    If you really want to know, it's easy enough to look at the owners manuals online for the models that interest you.
  • sussamb 813 Points
    If there is a pause feature on the Etrex I haven't found it ;)
  • DaveM 159 Points
    edited October 2015
    sussamb said:

    If there is a pause feature on the Etrex I haven't found it ;)

    If it's there I haven't found it ether. I think that is one of the things that went away between the old eTrex models and the 10/20/30. I could pause my Legend.
  • sussamb 813 Points
    edited October 2015
    Not sure I ever found it on my Legend either :))

    Going back to the OPs problem, one way that might help is to in Setup, Tracks under "Record Method" select "Distance" and an interval of 0.01. This means your Etrex will pause and not record anything until you move 53ft.
  • Boyd 1985 Points
    I was talking about devices that were introduced after the Oregon 600, such as the eTrex x and touch series, not the 10/20/30. ;)

    But I had a quick look at those manuals and I don't see a pause function there either.
  • one way that might help is to in Setup, Tracks under "Record Method" select "Distance" and an interval of 0.01. This means your Etrex will pause and not record anything until you move 53ft.
    I think I tried that, but will give it another go when I get the chance.

    I contacted Garmin about the problem and they suggested setting the record method to "Time" and the interval to every second. All this did was drastically increase the number of points and filled up the memory. I didn't see that it had any effect on the trip computer at all. It still way over estimated the distance traveled.
  • DaveM 159 Points
    sussamb said:

    Not sure I ever found it on my Legend either :))

    Tracks page near top Track Log "On" "Off" buttons.
    sussamb said:

    Going back to the OPs problem, one way that might help is to in Setup, Tracks under "Record Method" select "Distance" and an interval of 0.01. This means your Etrex will pause and not record anything until you move 53ft.

    It's worth a try but when I had a different problem Garmin asked me to try a Record Method other than Auto. I tried Distance and the track was vary bad and the distance was way off.
  • DaveM 159 Points
    I may have found A way. When you stop go into "Setup", "Tracks" and change "Track Log" to "Do Not Record" it will stop saving points. When you are ready to start moving change it back to "Record, Show On Map" or " Record, Do Not Show"

    I have been playing with this at home and it's working. I haven't had a chance to try it on a hike to see what the track would look like but think it would be good.
  • Boyd 1985 Points

    I contacted Garmin about the problem and they suggested setting the record method to "Time" and the interval to every second.

    The GPS chip provides one position update per second, so when you set the eTrex this way, it is capturing all the available data. My understanding is that the trip computer always uses a 1 second interval for the data it displays, regardless of what you set for the tracklog. Therefore, if you choose a different recording method for tracks, they may not agree with what the trip computer says.

    So I understand why they told you to do this, but don't think it really addresses your specific problem. You need to turn tracking off when you stop for a break.

  • privet01 215 Points
    I agree that their suggestion really doesn't address the issue. Based on post I've followed on Garmin's site, it seems to be those performing activities at very low speeds that have the most inaccuracies. And that seems to be those that average less than 3mph. With my Edge and my very old gpsMap76CSx, I've always had good results with walks, but I average more the 3mph.

    When you accept the fact that GPS accuracy is not what TV, movies and salesman claim then you can easily see that the situations you've encountered are times that will require extra effort on your part to enhance the accuracy of the data you collect.

    Stopping the track recording by some means is going to be main key. If your device doesn't provide an easy way to pause recording then turning the unit off or going into the settings and stopping the track recording/logging is your only choice.

    Also, as Sussamb suggested, changing the recording method to "distance" and selecting a value that high enough to get you out of the 30 foot or so circle of error that all recreational consumer devices must live with should help. I do a similar thing with my Edge 500 and let it automatically pause my timer (which stops recording track and other data) when my speed falls below 3mph. As on a bicycle then only times I'm that slow is when I'm stopping or starting.
  • privet01 215 Points
    I occurred to me today that your concern is likely more in the totals and such you see on your device. In that respect, changing the recording or logging method is unlikely to do anything for that. It should help make for more correct distance values when you upload your data and view it on your computer. But that also depends on the software or website you view it with. Garmin's software and Garmin's fitness site tend you use the accumulated totals from your device. Certain other software and websites such as Strava.com will use the gps position data to calculate totals such as distance.

    At any rate the first two posts in response to your question are still your best bet. If you don't want to switch it off when taking a break, then at least stop the track recording by going into the setup.
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