Planimetric Update

Cecil County, MD Planimetric Update to Support e-911 and MS4

Weston & Sampson was selected by the government of Cecil County on the eastern shore of the Chesapeake Bay, to update their existing planimetric data across the county. This update was completed in order to support e-911 and other directives, including Municipal Separate Storm Sewer (MS4) compliance.

Planimetric data included impervious surfaces and a tree line geometry. Previous planimetrics had last been acquired four years prior, and the county had experienced enough growth to warrant an update. Weston & Sampson took receipt of 3-inch resolution aerial photography acquired separately by the county as well as the existing planimetric data and began to update the features.

Along the way, it was discovered that some optimizations could be made to clean up the planimetric features. Slivers were merged into adjacent features of the same surface type and overlaps were removed. Each type of surface was uniquely identified, and an additional attribute indicated the source year it was established so that if a feature hadn’t changed since the previous collection, it was easily filtered out.

The total number of orthophotograph mosaic tiles to be evaluated numbered 553, and the area of land to be reviewed totaled 418 square miles. Weston & Sampson delivered the project months ahead of schedule and on budget.

  • 418 square mile full county project
  • rapid turn-around time (< 3 months)
  • value added items - cleaned existing data
  • value added items - added update filter


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“I want to let you and your team know how much I appreciate your work on the Cecil County, MD planimetric project. The finished product exceeds our expectations, and I appreciate how efficiently the project was completed. I especially appreciate how independently you and your team worked. Finding a consultant who does the project correctly, on time, on budget, and doesn’t need their hand held is a rare occurrence these days.”

David Black, AICP, GISP | GIS Coordinator, Cecil County Government

Posted in GIS.