This paper summarizes work carried out in a project supported by the E
uropean Communities' Bureau of Reference (BCR) to develop reference so
ftware for finding best-fit geometric elements, under specified criter
ia, to coordinate data. The geometric elements considered are the line
, plane, circle, sphere, cylinder, and cone, The criteria for determin
ing the elements are, generally, minimum zone (MZ) and, where appropri
ate, minimum circumscribed (MC) and maximum inscribed (MI). The softwa
re developed implements methods founded on optimization, theory Two ap
proaches are described: the first implements mathematical programming
methods that exploit the particular structure of the problems consider
ed and provide a unified approach to their solution; the second, appli
cable to the MZ and, where appropriate, MC problems for the line [in t
wo-dimensions (2-D)] plane, circle (in 2-D) and sphere, implements a c
ombinatorial method that returns all global solutions.