Open Historical Map

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Available languages — Open Historical Map
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Ohm logo small.png

Open Historical Map (OHM) ( is an effort to use the OSM infrastructure as a foundation for creating the world's most universal, detailed, and out-of-date map. OHM will focus on the mapping elements where OSM excels - shores, political boundaries, buildings, and ways. Future and other efforts may engage in discussing actions, events, people, and movable items.

Note: As opposed to other projects such as OpenSeaMap, OHM makes use of its own database independent of OSM.

An early draft Open Historical Map/FAQ is available.

OHM Projects

List of Open Historical Map/Projects.

Editing OHM

OpenHistoricalMap data can be edited online using both iD and Potlatch. The iD editor is embedded within the OHM website.

Using JOSM it is necessary to alter the api connection parameter (uncheck the default): use (note http not https as on the OSM site).

How to map


start_date=* and end_date=*

Apply a start date and/or end date to the feature. The format is ISO 8601 format YYYY-MM-DD

If you don't know the actual day, you can just add the year start_date=1925


  • 1901-01-20
  • 1902-12
  • 1878
  • before 1910-01-20 (before a specific date - possibly when a photo was taken)

Tracing from Imagery

An example URL for a Tile Server is The URL template from that source would be{z}/{x}/{y}.jpg

JOSM - works with WMS Server, Tile Servers and local images. See JOSM Imagery Guide for more information.

iD Editor - open the layers panel, click "Custom" and paste in a valid Tile URL template

Further Notes

For further in depth tagging of features, you may consider Comparison of life cycle concepts, in particular the date namespace suffix and the lifecycle prefix.

Google Summer of Code Proposal

A number of projects that are in the Wikimaps, OSM, OHM, Wikimedia area would benefit from the temporal flexibility in the OSM tool stack. This would allow us to use data across projects, using layers from multiple sources at different time periods. These projects include:

  • design a how-to map
  • Enhance iD and The Rails Port so that a JavaScript time/date slider can be added to control the time period that is of interest.
  • Enhance iD and The Rails Port so that meta-data hooks are added to the code that allow for custom deployments of both software. The intent is to support their use as dedicated user interfaces to certain applications (such as medieval walking path editing) while still using a generic data source.

Using the data

There are a variety of ways to use OpenHistoricalMap Data.

For smallish scale it is possible to download data using JOSM. Two alternatives nw exist for larger volumes of data or larger areas:

Short-term plans

Keys proposed

Related OSM Projects

  • OSM-4D (see German version -translation link on top- as English version needs more translation)
  • Historic - OSM Wiki page on Historic sites in general
  • Proposed_features/historic_event - Failed proposal for including events in the OSM database
  • Historic Objekts - An atlas of historic sites based on OSM
  • HistOSM - An atlas of historic sites based on OSM, out of the University of Heidelberg


OHM-related mashups