PMC Editing Wiki: Tools, Wilbur
These are the options to use when saving ArmA 2 Visitor 3 or ArmA 3 Terrain Builder readable lat/lon elevation text file.
Choose save as and select “Lon/Lat Text Mesh (*.txt)” file format. Then use Set to pixel, 0 decimal places, then if you like set output bounds min/max to elevations like -60 and 800 etc. Output bounds are minimum and maximum elevation or altitude your terrain will have.
See also Save File Format.