Extract altitude from photos and GPX track

[holgermappt]

When I first correlate a photo with the GPX track, the "Geotagged Images" window shows filename, altitude, and speed (and the photo, of course). Then the coordinates are stored in the photo (with the photo_geotagging plugin), the original image layer is deleted, and the photo is loaded again. Now just the filename is displayed in the "Geotagged Images" window. After the photo is correlated with the GPX track again, filename and speed is displayed. If a geotagged photo is loaded that contains the altitude, that altitude is not displayed, just the filename.

My enhancement request is to make the behavior more consistent and to display all available information.

1) Display the altitude after an already geotagged photo is correlated with a GPX track (if the altitude is available in the track, of course).

2) Extract the altitude from geotagged photos ("GPS Altitude" in EXIF header) and display it.

[bastiK]

In 5242/josm:

fixed #7711 - Extract altitude from photos and GPX track