what weird parcel geometry breaks my duals code?

[brelsford]

1. Identify what weird parcel geometries break the duals code. (too small? too long/skinny? disconnected?)
2. return a list of bad parcels?
   -can they be fixed by adjusting the threshold parameter without user interface?

-fix duals code to handle bad parcels?

[brelsford]

failure case 1: 1st weak dual is not planar. (happens for very long & curved parcels)
-fix: ??

failure case 2: my centroid calculator can fail for parcels in the S0 graph that are not represented by a polygon in the shapefile. This is because the centroid calculator relies on consecutive edge ordering, which is how shapefile polygons are stored but not necessarily how 'parcels' created by the spaces between polygons are created.
fix: write a function to check edge ordering.
the centroid caluclator can fail for small parcels with large coordinate values: fix is to do calculations on data that has been rescaled.