Using the Hausdorff distance to identify significant changes in polygon shapes

Our client presented us with a challenge of keeping two datasets in sync. One dataset was maintained by the GIS department and they are constantly in the process of updating the parcel boundaries. Sometimes these updates are small changes such as correcting the borders to match the property lines. Other times, these changes are significant. Significant changes can include merging parcels, splitting parcels or large corrections to the parcel shape. The other dataset is maintained by the maintenance department and it denotes which parcels they must go out and do a maintenance task on. This maintenance dataset was originally derived from the GIS dataset, but all synchronizations were being done manually. The main challenge is that if a parcel was previously a maintenance parcel and it has been merged or split, then a decision must be made on whether the new parcels are still considered maintenance parcels. This presentation will show how you can use the HausdorffDistanceCalculator transformer that is on the FME Hub, and some of the properties of the polygons to determine which changes are large enough to need to be reviewed. Anything that does not meet the threshold is automatically passed into the maintenance dataset, and anything that meets the threshold is passed into a “needs review” dataset. This immensely reduces the amount of data that the reviewer must look at and makes our client successful by saving them a ton of time.