Parcel Data In OpenStreetMap?

We really want a nationwide consolidated, standard parcel database to build upon. Such products are available from numerous proprietary data vendors who make it their business to routinely gather and consolidate data from local government agencies around the country. Of course these are often expensive and have restrictions on redistribution. Our federal government has a clearly stated and persistent vision of creating a nationwide public domain parcel database, and has made notable albeit slow progress towards this goal. Many states have managed to consolidate parcel data (e.g., Massachusetts, Montana). This is very helpful, but plenty of work is required to adapt tools or research from one state to another. And many states have no such offering. As a result, parcel data users for whom proprietary sources are too restrictive or expensive go about manually gathering the data from county agencies. If the application doesn’t span county lines, and if the county is open with their data, this may not be a problem. But these two conditions are often not both met, driving a more intensive data gathering effort. Such efforts are often duplicated for different projects.

Even when parcel data is made available openly, it often varies dramatically in quality and consistency. Some of these defects require local knowledge to be corrected. For example, if the number of dwelling units for a specific parcel is absent or implausible, this information could be corrected by an observer on the ground if a suitable interface were available. The same interface could be used by multiple organizations and individuals who use parcel data to integrate whole county datasets. These users could benefit from any tools or processes that grow around this open data. Obviously (or maybe not obviously), what I am proposing is inspired by OpenStreetMap (OSM), the wiki street map of the world that has been built on these principles. Some digging through the OSM mailing lists reveals some often controversial cases in which whole parcel datasets have been contributed to OSM. The concerns include some limitations on the existing OSM tool chain, reconciling future bulk updates from a jurisdiction with user-edited data, and the practical limitations of on-the-ground users improving or validating parcel boundaries. A subsequent correspondence that we initiated revealed strong interest in open parcel data from the OSM community, but mixed opinions about whether OSM was a suitable repository for such an effort. In light of this, we have decided to pursue the development of a separate open parcel data repository. So it begins.

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