Big discrepancy between FIT and GPX file total distance, and as displayed on Trip Computer

This problem is unresolved with software version 9.60. This is very disappointing, an accurate total ascent figure is a pretty fundamental GPS measurement. 

The GPSMAP 66i most current Firmware version is 8.80, not 9.60.

Yes, but this is the GPSMAP 66i forum. Posting information about other devices here may confuse some readers....

Sorry, but I thinks it's the same problem across the 66 range.

I think the ”distance” issue works ok  by now. I tested the distance tracking in a long 10 days hike in August and I was very happy to learn the distance was measured correctly (ver 8.5). I didnt test the previously described ”altitude issue” - so I do not know not if this is still an issue or not. 

But the other devices don't have equivalent forums of their own.  That is why some of us bring problems that ought to be common across the line.

For clarity:

6653023 said:

This problem is unresolved with software version 9.60. This is very disappointing, an accurate total ascent figure is a pretty fundamental GPS measurement.

Wrong device, wrong complaint. 

This is the GPSMAP 66i forum, and this thread is discussing FIT vs GPX distance issues, nothing related to ascent.

The GPSMAP 66i does not share the same firmware as found on the GPSMAP 66s/st/sr models. 

The issue with an incorrect total ascent has been discussed on this forum, not just for the 66i, but also for the 66s. See the post from RosscoP from 11 months ago and subsequent posts.

From this post:

The problem with the GPSMap66i and GPSMap66s units that I have been testing is that when you record an activity the elevation data and distance is often over exaggerated, I have just tested both units on a 13.5 mile hike this weekend , both units have the latest firmware updates that came out last week 

Both the fit file and gpx file showed a distance of 14mile and elevation gain of 1580 feet, in Garmins basecamp software if you delete any single recorded point from the fit file or gpx file the distance drops to 13.5 and elevation gain to 1300 ft, these refreshed figures are what I would have expected to see, as the track point removed was only a couple of feet away from the point before and after and also had the same elevation data as the points either side it looks like I was just forcing basecamp software to recalculate the recorded data.

I also imported the raw gpx and fit files into some other none Garmin mapping softwares that I use and interestingly the data shown was the 13.5 miles and 1300ft elevation.

In Garmin connect which shows the 14miles and 1580ft elevation if I select the option to trim file and simply take out the last 10 seconds ie couplemof track points the same things happens the figures sort themselves out to the correct distance of 13.5 miles and elevation of 1300 ft.

I looks like the data in the devices is being recorded correctly but the summary calculatiion that you see as the totals is calculating incorrectly, but a forced refresh of the data in basecamp by deleting any single point corrects the summary totals.

One thing that does seem to be fixed in the last firmware update is that both the .fit activity file and .gpx track recording file are now showing the same distance and elevation recording data , before the update last week there would nesrly always be big differances in distances and elevation data between these two files but this does seem to be fixed now.

Just the issue with the summary totals calculation which.looks like it still has a bug in it.