This paper indicates the advantages afforded when an analytical plotte
r is interfaced with a three dimensional CAD system. Problems associat
ed with combining various data sources (ground survey, aerial and clos
e range photography) of differing quality will be discussed, together
with compromises required to idealize the geometry of the real would e
nforced by a CAD system. The paper is illustrated by some of the comme
rcial projects undertaken by the Engineering Photogrammetry Unit at Ci
ty University. Applications of particular financial significance inclu
de modelling of petro-chemical plant for different purposes and to var
ious levels of derail and accuracy.