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PETERYAO
08-10-2009, 10:12 AM
It is a new 310XT, first time use. I got 19.97 miles reading out of an 18 miles course but with a correct starting point and ending point on map. Could this be caused by a software bug?

I powered on 310XT while driving (so it can acquire satellites) prior to the run, and I did not hit the START button. After I completed 18 miles run, uploaded data to connect.garmin.com, it displayed total 19.97 miles with correct starting and ending points on map. I know for sure, itís an 18 miles course, and others runners got 18 miles on their GPS. Could GPS got the extra 1.9-miles from the distance between where I powering on 310XT while driving and the parking lot? The timing was bogus; it displayed 01:20min/mi Best Pace for running?

Thanks for your input!

NDURANCERIDER
08-10-2009, 10:17 AM
Can you post a link to your activity or attach the TCX file to a forum message?

Have you updated your 310 to the latest software (https://buy.garmin.com/shop/store/downloadsAgree.jsp?product=010-00741-00&cID=142&pID=27335)?

April

DW152
08-10-2009, 10:35 AM
It's not really clear when you hit the start button. You said you didn't hit it when you started running, but did you hit it when you powered it up? 1:20 min/mile is 46 miles/hour, which is a reasonable speed for a car. The best thing would be to upload this run and look at the track to see if it included any time while you were driving.

PETERYAO
08-10-2009, 12:00 PM
Can you post a link to your activity or attach the TCX file to a forum message?

Have you updated your 310 to the latest software (https://buy.garmin.com/shop/store/downloadsAgree.jsp?product=010-00741-00&cID=142&pID=27335)?

April

1) activity link:
http://connect.garmin.com/activity/10805749

2) yes, I think my 310XT is running the latest software (last check 08/01/2009)

Thanks

NDURANCERIDER
08-10-2009, 12:21 PM
On first glance, I don't see anything wrong.

Your splits don't show a big issue, either. You already said the map looks drawn correctly.

I don't have time for in-depth analysis right now, though. Maybe somebody else does. I would look for irrational jumps in distance between track points.

Was this a race? Were you running with other runners at the time? That had GPS units?

April

PETERYAO
08-11-2009, 09:12 AM
On first glance, I don't see anything wrong.

Your splits don't show a big issue, either. You already said the map looks drawn correctly.

I don't have time for in-depth analysis right now, though. Maybe somebody else does. I would look for irrational jumps in distance between track points.

Was this a race? Were you running with other runners at the time? That had GPS units?

April


It was not a race & there were other runners with Garmin GPS and all with 18 miles on their GPS.

Because I set Auto Pause feature on during the run, now I would suspect the extra 2 miles, or 11% inaccuracy over the 18mils course were caused by the use to of 310XTís Auto Pause feature. Could it be the Auto Pause / Start actions generated many (18 out of 20) bogus extremely fast Max Speed on the splits? I donít know what algorithm 310XT use to determine the total running distance, but if it factors these 18 bogus Max Speed in, it could add up to 1.97 miles in distance. Again, this just an assumption and I did not see anything mention in the 310XT Ownerís Manual about how Auto Pause feature affects accuracy over a long run? Would you know?

Thanks

NDURANCERIDER
08-11-2009, 10:41 AM
Auto Pause shouldn't affect the distance. If it does, it's a bug and needs to be reported to support.

Don't suppose you can go run the 18 miles again with Auto Pause off? :D Possibly doing some shorter, controlled experiments might show you? Sounding like you might want to raise this to support (http://www.garmin.com/garmin/cms/site/us/support).

April

SEILOGRAMP
08-11-2009, 03:29 PM
FWIW, I looked at the run. I noticed some weird movement just before mile 6. I looked at the trackpoints, some of them appeared to be going back in time.:confused:
https://forums.garmin.com/attachment.php?attachmentid=180&stc=1&d=1250026519

FRANCISSEDGEMORE
08-12-2009, 05:28 AM
Maybe the device registered a running speed greater than 2.998x10^8 metres per second – a short, sharp dash.


FWIW, I looked at the run. I noticed some weird movement just before mile 6. I looked at the trackpoints, some of them appeared to be going back in time.:confused:

PETERYAO
08-12-2009, 09:42 AM
FWIW, I looked at the run. I noticed some weird movement just before mile 6. I looked at the trackpoints, some of them appeared to be going back in time.:confused:
https://forums.garmin.com/attachment.php?attachmentid=180&stc=1&d=1250026519




That was a restroom break, indoor no or weak GPS signal. Auto Pause should be on at that time?

KANSAIBEN
08-12-2009, 09:54 AM
That was a restroom break, indoor no or weak GPS signal. Auto Pause should be on at that time?

Auto-pause needs a good GPS signal lock to work properly or else, in the case shown here, GPS drift can cause the unit to believe it is moving. Would suggest that if you head indoors for a nature break you might just want to hit the stop button. And before you start up again, make sure you've got a good signal again. One reason I set one of my data fields to show my GPS accuraccy.

PETERYAO
08-12-2009, 07:10 PM
Auto-pause needs a good GPS signal lock to work properly or else, in the case shown here, GPS drift can cause the unit to believe it is moving. Would suggest that if you head indoors for a nature break you might just want to hit the stop button. And before you start up again, make sure you've got a good signal again. One reason I set one of my data fields to show my GPS accuraccy.

Thanks for the tip. Paying attention to GPS signal strength is the key.

DW152
08-13-2009, 07:15 AM
A similar thing (GPS losing track) happened to me about the second or third time I used my 310. It happened after I had been running under some heavy tree cover; when I emerged it lost the track and never recovered. However, I did do a full reset shortly after that race, and ever since then it's been pretty solid.

PETERYAO
08-14-2009, 07:52 AM
Auto Pause shouldn't affect the distance. If it does, it's a bug and needs to be reported to support.

Don't suppose you can go run the 18 miles again with Auto Pause off? :D Possibly doing some shorter, controlled experiments might show you? Sounding like you might want to raise this to support (http://www.garmin.com/garmin/cms/site/us/support).

April

Did a 12 miles run without using Auto Pause, it got way much better this time, no more bogus Max Speed on all 12 splits and got a correct 12 miles total. I would advice think twice before turning on Auto Pause on your 310XT, unless you want to show off you can run 1:20min/mile pace. As to if Auto Pause affects total distance accuracy over a long run? I think it will, but you are welcome to try it & share.

NDURANCERIDER
08-14-2009, 10:54 AM
It would be good for you to report your findings to Garmin support, so it can be logged.

April