I've developed some algorithms that work with GPS trajectories. So I need a repository in which I can download GPS trajecotries to run my test.
I most need marine and air tajectories, better if fileformat was a .gpx.
GPS track logs for vessels can be accessed using AIS.
Ships broadcast information such as GPS position, heading, and speed. Updates are sent over radio at periods of between 2 and 30 secs for a moving ship.
Data can be accessed on sites such as aprs.fi who provide an api, although not in GPX format. Many commercial sources also exist that can provide historic data.
You can get cycling activities from Strava in JSON format using this url:
Activities and users are freely browseable.