Mathematical Models for Measuring Geographical Compactness
In Commonwealth ex rel. Specter v. Levin, 448 Pa. 1, 293 A.2d 15 (1972), the Supreme Court explained what is required for a reapportionment plan to be "compact" and "contiguous."
A district is contiguous if a person can go from any point in the district to another point in the district without leaving the district. Id. at 17-18, 293 A.2d at 23.
Stated otherwise, one glance at the map ought not to reveal any district "islands."
Compactness is more difficult to achieve and, thus, there is a "certain degree of unavoidable non-compactness in any apportionment scheme." Id. at 18, 293 A.2d at 23.
Specifically, a "determination that a reapportionment plan must fail for lack of compactness cannot be made merely by a glance at an electoral map and a determination that the shape of a particular district is not aesthetically pleasing." Id. at 18, 293 A.2d at 24.
The Supreme Court noted in Specter that mathematical models have been developed for measuring geographical compactness, but it did not endorse any of them.
A standard for compactness has yet to be announced, and our courts have yet to set aside a municipal reapportionment plan for lack of compactness.