The elev.0.5-deg_tbase.txt data is elevation data at 0.5 degree lat-lon
resolution. There are 720 and 360 grid points in the x and y direction,
respectively. 

The x direction is longitude, which starts at 0.25E and goes to 359.75E
(0.25W). The y direction is latitude, which starts at -89.75 (89.75S) 
and goes to 89.75 (89.75N).

As before, the data was written as 360 rows and 720 columns, starting 
from the lower left corner, i.e., 89.75S; 0.25E to the upper right 
corner, which is 89.75N; 359.75E (0.25W).

Unit is meter (m). Undefined is set to -999.