The Collaborative International Dictionary of English v.0.48:

Ichnography \Ich*nog"ra*phy\, n. [Gr. ?; 'i`chnos track,
   footstep + ? to describe: cf. F. ichonographie.] (Drawing)
   A horizontal section of a building or other object, showing
   its true dimensions according to a geometric scale; a ground
   plan; a map; also, the art of making such plans.
   [1913 Webster]