[gembud] determining model terrian height

Seems like I should know this, but I don't.  I wrote a gdvint script that 
interpolates GFS/NAM/RUC data to height above ground for 300 meters above 
ground.  It then occurred to me that I don't know what the particular model 
thinks is the elevation at my chosen grid point.  I did a gdinfo for the 
nam212, gfs212, and ruc255 and did not see anything that might give me model 
terrain height at a given grid point (say using gdpoint).  Does anyone know how 
to do this?

Robert Mullenax