OpenStreetMap Baltimore City Buildings and Addresses Import

Two years ago, I started trying to import building footprints and addresses provided by the City of Baltimore into OpenStreetMap but was held up by red tape and eventually gave up.1 The City provides building footprints and parcel data on their open data portal; the download pages for these two datasets list the data as public domain, but the site’s terms of service is the same as the rest of City’s websites, saying the data is copyrighted. I had worked through the technical aspects of preparing and simplifying the building footprints for import and had started working on how to associate addresses from the parcel data but eventually gave up after I was unable to secure the needed licensing clarifications from the Mayor’s Office of Information Technology (MOIT).

This past fall, Elliot Plack, who then worked for Baltimore County GIS and was appointed to the Maryland Open Data Council by Governor O’Malley, got in touch with me about restarting the import, after finishing an import of similar data for the County. After meeting with Jim Garcia from MOIT, he was able to secure the permissions that we needed to proceed with the import. Additionally, he was able to get address point data, which is much superior to and easier to use than the parcel data I was originally going to extract addresses from.

With the address data in hand, I worked through the remaining technical aspect of the import in January and February with help from Elliot.2 Besides simplifying the building footprints,3 footprints intersecting existing footprints needed to be separated out, and addresses needed to be added in. Where buildings didn’t intersect existing footprints and only contained one address point, the address was merged into the building. Addresses that were contained in intersecting buildings were also separated out. Address data also needed to be translated into OSM tags. We decided to automate the import as much as possible, with non-intersecting buildings and addresses to be uploaded via script. Conflicting data would then be manually conflated and uploaded.

About a month ago, with the preparation done, Elliot sent an email to the OSM Imports and US Imports lists announcing the restarted import. After receiving no objections, I executed the automated portion of the import a week and a half later. A job was then set up on the tasking server for the manual portion of the import,4 which is currently underway. Elliot and I as well as a couple other local mappers have been working through this portion of the import and should hopefully be finished in the next month or two, which will conclude the import.


  2. The code used for the import is on GitHub

  3. This is an interesting problem, since the topology of adjacent row houses needs to be accounted for. 


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