based on your comment here
http://discuss.ardupilot.org/t/using-our-own-vertical-data-for-mission-planning/12546/17
you don’t understand how the system works.
ter_? is the terrain system. it could be srtm or it could be geotiff. it is the same thing. this is just indicating to say if it has terrain data or not. it doesn’t care where the data is from. when you set the spacing to 1, it pulls from the geotiff, if available and uploads that at 1m resolution