ICHNOGRAPHY (Gr. 'lxvos, a trace, and rypacn, description) , in architecture, a term defined by Vitruvius (1.2) as "the ground-plan of the work," i.e. the geometrical projection or horizontal section representing the plan of any building, taken at such a level as to show the outer walls, with the doorways, windows, fireplaces, &c., and the correct thickness of the walls; the position of piers, columns or pilasters, courtyards and other features which constitute the design .