The Collaborative International Dictionary of English v.0.48:

Planimetry \Pla*nim"e*try\, n. [Cf. F. planim['e]trie.]
   The mensuration of plane surfaces; -- distinguished from
   stereometry, or the mensuration of volumes.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

21 Moby Thesaurus words for "planimetry":
   altimetry, bathymetry, biometrics, biometry, cadastration,
   cartography, chorography, craniometry, geodesy, geodetics,
   goniometry, hypsography, hypsometry, mensuration, metrology,
   oceanography, psychometrics, psychometry, stereometry, surveying,
   topography