Use the "terrain load" command to import these datafiles.
They are stored as Float-32 arrays, use the F32 import type.

These files are formatted on a scale of 0 to 1, they are designed for a range of 0..77.14
use the 'multiply' command to multiply them by 77.14 to achieve correct height values.

Example ------------------
Region# : terrain load f32 c:\opensim\datafiles\output_x0_y0.r32
Region# : terrain multiply 77.14