This chapter defines a distance function that measures the
dissimilarity between planar geometric figures formed with straight
lines. This function can in turn be used in partial matching of
different geometric figures. For a given pair of geometric figures
that are graphically isomorphic, one function measures the angular
dissimilarity and another function measures the edge length
disproportionality. The distance function is then defined as the
convex sum of these two functions. The novelty of the presented
function is that it satisfies all properties of a distance function
and the computation of the same is done by projecting appropriate
features to a cartesian plane. To compute the deviation from the
angular similarity property, the Euclidean distance between the given
angular pairs and the corresponding points on the $y = x$ line is
measured. Further while computing the deviation from the edge length
proportionality property, the best fit line, for the set of edge
lengths, which passes through the origin is found, and the Euclidean
distance between the given edge length pairs and the corresponding
point on a $y = mx$ line is calculated. Iterative Proportional
Fitting Procedure (IPFP) is used to find this best fit line. We
demonstrate the behavior of the defined function for some sample pairs
of figures.