Use this to generate terrain to put on your SD card. There are 2 dataset versions available:
Multiple generated files of the same dataset version can be combined on the SD card.
Compatible with Ardupilot 4.1+
To download entire continents of SRTM3 terrain data, see here.
If using the SRTM1 data, set ArduPilot's TERRAIN_SPACING parameter to 30 before loading the data to the SD card.