gpxelevations is a utility commandline tool to add/update elevations in a GPS track file:

$ gpxelevations -h

usage: gpxelevations [-h] [-o] [-c] [-f FILE] [gpx_files [gpx_files ...]]

Adds elevation to GPX files

positional arguments:

gpx_files GPX files

optional arguments:

-h, --help show this help message and exit

-o, --overwrite Overwrite existing elevations (otherwise will add

elevations only where not yet presetn)

-c, --calculate Calculate elevations (but don't change the GPX file

-f FILE, --file FILE Output filename