This document discusses the Open Historical Map (OHM) project. It provides an overview of OHM's goals of creating a detailed map of history, describes some differences from OpenStreetMap like encouraging mapping of no longer existing places and use of start/end dates, and provides examples of potential OHM mapping projects focused on military history, diversity, and synthesizing OHM and OSM data. Communication channels for the OHM project are also listed.

1. Richard Welty
Mappy Hour - 2020-07-08
Open Historical Map

2. The Goal
… is to create the world's most
universal, detailed, and out-of-date
map

3. The Reality
• There is much blank space in OHM
• There is more than enough of history after all
• There are some very detailed areas

4. Projects
https://wiki.openstreetmap.org/wiki/Open_Historical_Map/Projects

5. Projects

6. What’s the same as OSM?
• The database schema
• Editing API
• The editors
• Fork of iD on the Open Historical Map website
• Easy to con
fi
gure JOSM to access OHM instead of OSM
• Our own instance of Overpass, unmodi
fi
ed
• OSM tagging largely relevant

7. What’s Different?
• Mapping things that no longer exist is encouraged
• Mixed licensing model (license tag)
• CC0 encouraged
• CC-BY-SA is ok
• mass copying from OSM is a bad idea because of the way ODbL works
• start_date and end_date tagging is important
• Care with sourcing - we are acting as Public Historians
• Documentation of active projects in the Wiki is encouraged

8. What’s Different?
• Vector tiles with the Time Slider
• new with the recent reconstruction of the site
• Time Slider uses start_date and end_date to determine what to display
• start_date & end_date
• currently ISO date formats supported (yyyy-mm-dd)
• will be extensions in the future

9. Timeslider demo

10. Editing
• When all of history is in front of you in a map editor, information density can
become insane, or at least a bit unwieldy
• JOSM
fi
lters o
ff
er some help
• compare start & end dates to particular years
• iD may have
fi
lter support coming to help
• not ideal in current form, but usable

11. Tagging Experimentation
• no equivalent to OSM tagging list and tag voting
• we are on a learning curve with respect to historical tagging
• currently working with relations as ways to show di
ff
erent con
fi
gurations over
time
• use of street relation proposal or associatedStreet relation as ways of
grouping ways in to streets that may have changed name, paving condition,
classi
fi
cation, or status over time
• use multipolygon same way for areas that change over time

12. Sourcing
• modern sources (Bing, Mapbox, ESRI, etc.) of limited value
• permissions may not extend to OHM
• Mapbox and ESRI have responded positively to our requests
• most importantly, stu
ff
we want to map is often not in modern imagery
• historic sources are everywhere
• Libraries, Universities, Historical Societies, Museums
• May or may not be geo referenced
• mapwarper.net
• for maps and aerial imagery that is not available in georeferenced form (TMS, WMS, WTMS
URLs)

13. Sourcing Dates
• Easy to say “start_date” and “end_date”, harder to do
• maps and aerials o
ff
er point-in-time information
• use external written documentation where found
• build date ranges by referencing multiple sources
• in Albany, I’m looking at a wealth of maps at various points in time
• access your local historical community

14. OHM project mindset
• long and medium term projects
• can’t
fi
nish it quickly by looking at bing and maybe driving out for a ground
survey
• plan on gradual improvement as knowledge develops
• wikipedia can be a research start point - but probably never an end point
• follow and verify citations
• when you
fi
nd problems in wikipedia, you do actually have the power to
address them - if you’ve done the research

15. Examples - military history
• Munin project
• WWI
fi
eld forti
fi
cations
• American Civil War
• Gettysburg
• Antietam
• potential for driving animations

16. Examples
• Diversity
• Seneca Village (NYC)
• Rapp Road Historic District (Albany NY)
• Potential diversity projects
• Tulsa OK - Black Wall Street as it was
• other majority minority communities of note
• deed restrictions

18. Examples
• OHM-OSM synthesis
• Monument/Statues
• migrate monuments/statues to OHM as they are removed
• document start & end dates, other properties
• Ghost Tracks
• race tracks of the past

19. Online presence
• historic@openstreetmap.org mailing list
• OSM US Slack
• OSM Discord
• @OpenHistMap twitter
• OpenHistoryMap Facebook group
• #ohm on irc.oftc.net
• may be retiring irc channel