BasicAirData GPS Logger
Offered by BasicAirData - Open and free DIY air data instrumentation and telemetry.
BasicAirData GPS Logger is a simple App to record your position and your path.
It's a basic and lightweight GPS tracker focused on accuracy, with an eye to power saving.
This app is very accurate in determining your altitude: enable EGM96 automatic altitude correction on settings!
You can record all your trips, view them in your preferred Viewer (it must be installed) directly from the in-app tracklist, and share them in KML, GPX, and TXT format in many ways.
The app is 100% Free and Open Source.