Source : Webster's Revised Unabridged Dictionary (1913)

Hypsometry \Hyp*som"e*try\, n.
   That branch of the science of geodesy which has to do with
   the measurement of heights, either absolutely with reference
   to the sea level, or relatively.

Source : WordNet®

hypsometry
     n : measurement of the elevation of land above sea level [syn: {hypsography}]