OpenHistoricalMap is building an OpenStreetMap-like map of the world across time. We’ve bolted the time dimension to OSM’s data model and software. So far, we mostly got away with it, but cracks are starting to show. For example, merely attempting to edit OHM in some cities can incur rate limits. Boundary changes over time result in massively redundant data, hurting the end user experience.

This comes during something of a renaissance for historical GIS. New projects are popping up everywhere, but other projects lack the special community ethos of OHM. Laypeople are also discovering historical mapping as a new frontier for geospatial knowledge. We’re coming into this scene with a bare-bones operation. Just a few developers support hundreds of thousands of map contributors who depend on the software to just work for them, or else they’ll resort to ugly hacks in desperation. We need the broader FOSS4G community to pitch in with ideas, technologies, and code to help us ensure that the next generation of historical maps is based on open data and open source software.