GPSMAP 66i Loss of information if file is imported in Explore Collection

This may depend on whether you import the .GPX as a route or a track. Tracks are imported intact. Routes are "thinned" (to no more than 200 points) if the original .gpx contains more than 200 points. Yes, I know, it makes no sense. Apparently this is a nod to less capable devices (wearables?) which are also part of the Explore eco system. Least common denominator apparently rules.

You might try it as a track if you have not done so.

I know it does not fit your use case, but I usually just drop the .gpx onto the unit via the Windows file system. Beyond a certain point, it's just not worth the effort to deal with Explore vagaries.

Thank you for your answer. I import the .GPX file as a TRACK. I do not have a PC when traveling, and I do not know how to copy a .GPX file from a smartphone to a GPSMAP without PC. One way to copy a file is tu extract SD Card from tge GPS, insert it in the smartphone , copy file(s) in SD Card, and re-insert it in the GPS, but it seems a lot of work and at the end risk of spoiling devices

I can't account for the loss of information for a track. With the exception of time, all of the missing data is associated with elevation. If you look at the elevation profile (3rd tab), does the imported file seem to include elevation information? Complete loss of elevation information would definitely be a bug.

I think that the aggregate data (total ascent/descent, max/min altitude) is not part of the .gpx standard schema. It's either computed by the device OR (if present in the .gpx), it's in a Garmin extension. Maybe Explore does not recognize the extension and discards it? That would be standard behavior for XML file processing when an unrecognized construct is encountered.

Hi, the third tab is correct, it shows the same chart using Collection or the file copied in the directory. I agree, there is no information in .GPX file about maximum  and minimum elevation. But I use the same file used in both cases, with different results. It seems to indicate that the GPS compute max and min elevation, and duration (?) when importing a file from the ..\GPX directory, but does not compute when using a collection. This seems weird to me, I will ask Garmin.  Thanks for help

There ARE Garmin extensions for the track statistics. You can find the extension schema here;

https://www8.garmin.com/xmlschemas/TrackStatsExtension.xsd

These are the statistics which the extension accommodates:

I have not found an example of their use in one of my own .gpx files on the 66i, though. 

If you have the .gpx file, open it in notepad to see if the extensions are included. If so, the issue is almost certainly that Explore does not recognize them and is dropping them.