What is OpenHistoricalMap?

OpenHistoricalMap tries to gather data, which does not belong in the OpenStreetMap database, but still should be in some map. There are some objects in the OpenStreetMap database which would rather belong into the OpenHistoricalMap. A typical example is historical railway tracks, which had been disassembled. In short terms, OpenStreetMap gathers data of things which are there, OpenHistoricalMap gathers data of things which had been there and (!) have some historical significance.

What sort of data belongs in OHM?

You can add any map data, which is historically relevant. As a rule of thumb, any data, which could have its own wikipedia article can be added. Furthermore, you can add data from maps, which are in some way important, like the maps of Martin Waldseemüller (map_author = "Martin_Waldseemueller"). But always consider, that it must be filtered easily. Sources can be maps, of which the copyright expired (be sure, that it applies worldwide).

Do you have some examples?

What is the relationship between OHM and OSM?

OHM uses the tools and data structure from OSM, such as the website and JOSM and iD editors, with modifications where needed for storing and filtering time-based data. Though the data in OHM is in an OMS-compatible format, it is not directly connected to the data in OSM nor is data automatically interchangeable between the two systems, since there are differences in licensing. In 2021, OHM became a "Charter Project" of OSM-US in recognition that the OHM project helps expand the use of OSM tools and will contribute improvements back into the OSM ecosystem.

Who runs OHM?

• Servers, Services: GreenInfo Network and Development Seed
• Github Org admins: Dan Rademacher, Jeff Meyer, Albin Larsson
• Social media (Twitter) and overall community engagement: Jeff Meyer

Why can't I use OSM for historical data?

Imagine a field, which was used as a quarry in the middle ages, later Wallenstein had his encampment in the Thirty Years' War there, then it was a forest owned by the Bavarian King, in the First World War it was a battlefield with trenches and today there is a shoe factory. If everything would be added there, it would be a part of the map flooded with polygons. At the same time, almost nothing of it would be rendered. That is by itself no real problem, but if the editors like ID don't support the concept of selected time scopes, adding a street lamp in ID is almost impossible due to the large number of nodes. The concept of this selected time scopes could be added, but will likely be not, since the OpenStreetMap project likely will stick to its original goals.

What is the best way to start adding data to OHM?

Just like OSM you have two options: Either load up data from JOSM, or go directly to openhistoricalmap.org. You need to sign up for an account and you can start mapping right after with ID. If you already have an account on OSM, you will need a new account, here as both systems are separate systems.

What can I use OHM data for?

Assuming someone put a lot of effort into adding all the Roman road network, then a teacher could use specific excerpts for the history lessons. This is a very simple scenario. A more advanced use case would be, to generate a navigable map of the Roman network. This could be used to analyse troop movements during Roman wars and probabilities of different alternatives.

Can OHM be used for building routing models?

Yes, because OHM uses the OSM data model and technology stack, it is possible to extract data from OHM and load it either in a native OSM format (XML or protobuf) into a range of open source routing tools which have been developed to use OSM data. These include Gosmore, Graphhopper, and OSRM. Choice of which routing engine will depend on application: some use contraction hierarchies which limit routing to a single transport mode, whereas others can be configured to provide several routing modalities (e.g., foot, horse, horse-and-wagon etc.).