Unlock achievements by comparing and voting for the best building footprints from two sources in San Juan County, WA.
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San Juan County Building Footprint Review

A simple web application for comparing and voting for the best building footprint from two sources in San Juan County, WA.

Source code available on GitHub

Why are we doing this?

San Juan County GIS has two sources of building footprints.

  1. SJC Footprints (Map 1) is a layer that has historically been updated by GIS staff and interns. Due to reductions in staffing, we have not updated the layer in several years so new buildings, additions and demolitions may not be included.

  2. Pictometry Footprints (Map 2) contains features that were automatically generated by proprietary remote sensing algorithms from Pictometry International as a service to San Juan County. Since these were generated by algorithms we're hoping to get some human eyes to review.

Votes will be tallied for each footprint and the footprint with the higher number of votes will be in the final data. The final data will be published on the GIS Download page on the San Juan County website.

We will also publish the final results on OpenStreetMap.

How to contribute

Two maps are shown with the same aerial imagery (2016) but with different building footprints. Compare the footprints with the aerial photo and click the appropriate map button to vote for that footprint. If the footprints are identical, vote for Map 1.

If the building is too obscured in the aerial photo or otherwise difficult to see, click on the Skip button to load another footprint.

If neither footprint is accurate or otherwise needs manual review, click the Flag button. The GIS team will carefully review all flagged footprints.

Running it locally

  1. Install Node.js
  2. Clone or download and extract the repository
  3. From the command line cd to the repo directory and run npm install
  4. Important! - Change the three service URLs in the app.js file to .../Footprint_Compare_Test/... and remove the proxy parameters (the production URLs will not work locally)
  5. Run npm start and open your web browser to http://localhost:9000

Please submit pull requests on a new branch.


Copyright 2016 San Juan County GIS

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at


Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

A copy of the license is available in the repository's LICENSE file.