Try deleting one point and the distance will change. It might be a large or small change and it could be up or down. You can also click on the first point then hold down shift and click on the next to last point or use the second and last points instead of deleting a point. BaseCamp will then recalculate the distance and not use the number from the GPS. This new number should be correct. Garmin has a bug in it's GPS units that calculate distance wrong. I don't know if all of Garmin's GPS models have this bug I know the etrex and GPSMAP 64 has it.
I agree that the OP was asking how to find the mileage in a track and you gave a good answer for that. I assumed the OP was looking at a track from a GPS and thought he/she should know it could be wrong. If I was incorrect and it's a track created in BaseCamp then it should be good.
As I think we've discussed before I've never seen the bug you report, both my Etrex 20 and Montana report correct distances. That's not to say that under certain circumstances some GPS may inaccurately report it, just that I've never seen it.
The Oregon 600/650 and GPSMAP 64 write a separate summary of the track data to a GPX file. BaseCamp will use the data from that summary unless you select every point but one in the track info, or when you change the track a little bit (by deleting one point). In those cases BC won't use the summary, but calculates the distance from the track itself; just as it does for devices that don't create a summary (all other devices except the sports models) The distance in the summary tends to be different from the calculated one.
I know you have never seen the bug. It is a bug that has been acknowledged by Garmin Tech Support.
They have seen it and have opened a case. For now the workaround of deleting a point to force BaseCamp to recalculate is easy to do. Sometimes it's a small error I wouldn't see if I wasn't forcing a recalculation or even care about. Other times it can be large more then doubling the distance. Until the bug is fixed I will check all me tracks and think others should do the same if they are interested in the mileage.
Iv'e seen it on both my etrex 20 and GPSMAP 64s and sent Garmin files from booth including some with different recording methods made at their request. I think it's a bigger problem with the 64s then with the etrex 20 but it's newer so hasn't been used as much so it could be bad luck Iv'e seen bigger errors on it.
From JaVaWa's post it seems it's limited to the 64 and Oregon 600/650 models which explains why I haven't seen it, although you say it also applies to the Etrex 20 :confused:
Yes Iv'e seen it on the etrex 20. I don't think it's as bad but that could be luck based on the amount of data I have. The etrex writes a summary of track data to the GPX file and based on JaVaWa's post that is the difference.
As Iv'e said in the past the problem seems to be at lower speeds. Any errors I've found at bike speeds are so small I never would have seen them if I wasn't checking based on finding the error hiking. I have a computer on my bike and the etrex 20 has always been so close to the computer I never would have questioned it.
Hiking sometimes it's so bad I know it's wrong before I even check. That's how I found it I was on a hike that showed more then double the mileage. I assumed I had reset it before getting a good sat lock. When I got home I loaded it in BaseCamp planing to delete the extra points before the trail head. When I loaded it it looked good so my assumption on resetting it before a lock was wrong. I then started playing and found that deleting a point would fix it. I tried the first, last and random points in the middle and it didn't mater which point it would then correct the mileage. I had hikes before this that I would think I went a lot father then I thought or I thought I went father then that but not bad enough that I investigated the files. After this I started checking all my files and they are always off sometimes not much and sometimes a lot sometimes high and sometimes low. The average speed etc is also off and will be corrected when you eliminate a point.
Unfortunately I don't keep all my files from local hikes and I don't hike much in the summer so I don't have a good date on when this problem started. I think it was sometime in late 2013 or 2014. all my older files look good.
