nfgusedautoparts's diary

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moving OSM data to OHM - dealing with the license

Posted by nfgusedautoparts on 4 August 2020 in English (English)

so something has gone away in the real world, and rather than just deleting it from OpenStreetMap, you’d like to move it to OpenHistoricalMap.

That’s a great idea, but don’t rush.

OHM and OSM have different licensing philosophies. The entirety of the OSM database is licensed under the ODbL and content in the database is licensed under the Database Contents License.

OHM has a mixed licensing philosophy. The license tag should be set on entities in the DB (high level relations or ways, no need to tag everything). Using CC0 (about the same as Public Domain) is preferred. Somethings may be licensed CC-BY-SA.

Because of this, there are steps you need to take.

First you need to examine the history of the object and find out who edited it (could be more than one person). Sometimes you’re fortunate and there is only one editor, which makes it easier. You will need to reach out to them, probably using the OSM messaging system, to find out if they object to their work being moved. Be respectful and nice, and explain clearly what you are doing. Emphasize that yorr goal is to preserve their work. Explain that it will need to be relicensed, preferably under CC0 (failing that, CC-BY-SA). You will find that many (most?) mappers are happy with this and will grant permission.

You will then need to hone your map editor skills, exporting the .osm file from OSM and importing it to OHM. Do not forget to add the extra OHM tags - license, source, start & end dates. Make sure you give credit.

Some things may be approached differently. For example, you may find that something predates the license change. In this case, it may well be available from the planet at If, for example, it is unmodified TIGER then it was originally public domain and is up for grabs. But if it’s unmodified TIGER, there is a fair chance an improved copy exists on the Census Bureau website so consider sourcing it there.

Imagery and Map sources - Old Maps Online

Posted by nfgusedautoparts on 8 July 2020 in English (English)

First in a series about ways to find imagery.


Old Maps Online is not so much a source, as a map enabled directory for maps. You go there, find the place you want using the map, and look at the panel on the right side of the browser for old maps.

None of these maps are hosted on Old Maps Online. They are in various repositories world wide. This makes it important to check copyright and licenses for the sites before using the imagery.

Some may have URLs that are usable in JOSM or iD already. Others simply have a way to retreive the map. In the later case you can use [] - see my diary entry with links to a number of youtube videos on Map Warper.

using mapwarper

Posted by nfgusedautoparts on 7 July 2020 in English (English)

i put together a couple of things on youtube showing various scenarios for using mapwarper. for folks new to OHM who want to know how to bring in source material that isn’t already geo referenced, this should help a bit.

1) In this one, i take a 1834 survey map of the Albany terminus of the Erie Canal, load it into mapwarper, rectify it, and then bring it into JOSM for editing:


2) In this one, i take an aerial image from 1952 which in theory contains the footprint of Clearview Speedway in South Westerlo NY (from USGS earthexplorer), bring it into mapwarper and align it. the scenario is a little different from the survey map, the image is much larger and a few issues show up that need to be addressed:


3) In this one, I look at what can be done to deal with the case where there is more than one map on a single scanned image, in this case something already scanned in on the NYPL website, but not quite usable as is: