For hundreds of years, humans have used maps for navigating to new worlds, charting unknown locations and recording histories. Today, the county uses building footprints in maps for dispatching emergency responders, planning land use designations, appraising property values and designing proper infrastructure. County maps are also used by real-estate professionals, delivery companies, transportation providers, developers and construction companies. As communities grow and infrastructure changes, maps need to be updated.

Building footprints are simple outlines of the exterior walls of buildings. Usually they are traced from building plans or aerial imagery and include eaves and overhangs. The county has two sources of building footprint maps. One source is hand-traced and has not be updated in several years. The second source was more recently traced using proprietary software without human input. We’ve studied some of the results of both sources and determined that one source is not always better than the other. So we need to compare each footprint one by one. With 18,000 footprints, this is no small task.

The county is asking for your help in reviewing our footprint data. Use the “Footprint Review” website at http://sjcgis.org/footprint-review/ to compare and select the better building footprint. Review and vote often to unlock “achievements” and brag to your friends. Your votes are tallied and saved and will be published in the final maps. The final footprint data will also be published on the county website.