1. A method of automatic spatial matching of models, the method comprising: providing, in machine-readable form, a first model comprising a definition of a three-dimensional solid; providing, in machine-readable form, a target model comprising a definition of the three-dimensional solid; identifying, using a processor, a first set of geometric entities in the first model that have a unique characteristic, including a first set of planar faces in the first model that have a unique area as compared to a set of other first model planar faces, wherein the unique area is unique when the unique area is within a predetermined tolerance, and including a first set of linear edges in the first set of planar faces; identifying, using the processor, a second set of geometric entities in the target model that have the unique characteristic, including a second set of planar faces in the target model that have the unique area as compared to a set of other target model planar faces, and including a second set of linear edges in the second set of planar faces; determining, using the processor, a best match between a member of the first set of geometric entities and a member of the second set of geometric entities by comparing the unique characteristic of the first set of geometric entities and the second set of geometric entities to form a comparison and minimizing an error function on the comparison, including determining a best planar face match, based on an area measurement, between the first set of planar faces and the second set of planar faces and a best linear edge match, based on a length measurement, between the first set of linear edges and the second set of linear edges; and computing a rigid body motion to be applied to the first model such that said first model is substantially coincident with the target model, wherein computing the rigid body motion further comprises: determining a midpoint and a tangent of matching edges from the best linear edge match: determining an outward normal of matching faces from the best planar face match; and determining a transformation matrix to place the master model based on a coordinate system comprising the midpoint, the tangent, and the outward normal.