Correcting King County’s City Limits Data

Authors: Floyd Bull*,
Topics: Geographic Information Science and Systems
Keywords: Geographic Information System, GIS, Python, Arcpy
Session Type: Poster
Day: 4/13/2018
Start / End Time: 1:20 PM / 3:00 PM
Room: Napoleon Foyer/Common St. Corridor, Sheraton, 3rd Floor
Presentation File: No File Uploaded

While counties and cities GIS departments work together, their data does not always match up. King County in Washington State has a city limits feature class within their public facing GIS portal. The City of Kent has an official city limits feature class that does not match the geometry of King County’s data. Kent wanted a way to replace the incorrect Kent city limits with the correct geometry. A python script was written to accomplish this task. The symmetrical difference tool was used to erase the overlapping geometries of the two feature classes. The output feature class still contains slivers of the incorrect Kent geometry. In total 75 slivers were created varying in size from 5 square feet to 500 square feet. These slivers need to be assigned to the correct surrounding city. Two issues arose when assigning these slivers. A couple slivers crossed over two different city boundaries, and some slivers border two or more cities. To address the problems the borders of the surrounding cities were extended by 40 feet. This allowed the script to split slivers that cross multiple cities boundaries. The longest side of the sliver was used to assign the sliver to the correct surrounding city. The script successfully corrects the King County’s geometry errors. The script is currently being turned into a generic tool. This tool can then be then used by any user.

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