This does mean that it becomes absolutely crucial for it’s usability that any edit (and potentially multiple versions or readings of a single area or detail) are traceable to source material. Otherwise it would become very difficult to place nay trust in that synthesis later on as a truly critical resource.

Yes, unlike OSM, we emphasize citing sources directly on individual features (as opposed to just in changeset metadata) and are gradually building out editor features to facilitate source management.

I did notice the difficulty about permission to use material for vectorisation. I’m a little confused as to what this issue extends to, since I’d think that one is free to vectorise whatever is feasible, but not free to the also publish the source material. I’m not an expert on such issues of rights, but it could become hairy pretty quickly. I also don’t think that all archives would properly expect this use of their material.

The situation likely differs from country to country, but copyright can restrict both verbatim republishing and derivation. We’ve been avoiding making full-throated claims of fair use, because of our international audience and the potential for incompatibility with projects that are less scientific or academic in nature. For the most part, we’ve considered out-of-copyright maps and sources other than maps to be safe. (For the latter, we lean on the principle that facts cannot be copyrighted.) Beyond that, we don’t have enough certainty to state a blanket rule yet, but this is all open to discussion.

Regarding de facto and de jure boundaries, I note you’ve opted for very explicitly legal terms. I’ve published on boundaries and used the philosophical concepts of fiat and Bina fide boundaries (of objects or spatial entities, derived from Smith & Varzi) in mapping. For representations of information on maps I continue to find this very useful.

These are very helpful terms – I may have to borrow them myself. Many of us are essentially self-taught, having gotten into history out of a sense of curiosity or even by accident, so we do need people with expertise to ground our experiments with thoughtful perspective.

Nonetheless, it would also be a real pity, historically speaking, if this would render such historical mapping sources essentially unusable. Personally, I feel that it is important to have vectorisations consultable next to geolocated and rectified raster maps for research purposes. In addition there could even be entirely reconstructive vectorisations, which then require marking up as interpretive reconstructions, placing a lot of emphasis on metadata and the process of making.

There is some wiggle room in terms of mapping competing boundary claims with claimed_by=*, or mapping representations in order to say they are false, using the not:* namespace, for example. But we are constrained in the fundamental data model we inherited from OSM: layerless, every kind of data about the world intermingled in one big pot. By even extending this model across time, we somewhat force ourselves to arrive at a definitive answer instead of simply relating every claim from existing sources.

Part of my interest in OHM was also to find out if it could be the right platform to potentially ‘release/disclose’ (some) of my research data. I’m not clear on that either so far. Possibly because the project wouldn’t respect the parameters set for OHM only an adjusted format of the vector data could become part of OHM alongside other ways of presenting and offering the data.

We’re thrilled that you’d consider us, even if we don’t end up being the main depository in the original format. Hopefully you’ll be able to find some benefit in a collaboration, whichever form it takes. As optimistic as I am about OHM, the reality is that we’re only one platform in a whole ecosystem of historical GIS. That’s why we strive to enable linked open data through Wikidata, FactGrid, QLever, etc. Platforms such as Pixeum and OldMapsOnline can complement the work we’re doing by presenting original source material in a manner that we’re ill-equipped to.

The daring requirement of features, while entirely logical and necessary, is also a tricky one. Very often the precise start and duration of any feature (not even entire spatial objects) is unknown, and historically speaking it would be very useful to have the source that claims the appearance, alteration, or destruction/removal of spatial entities. This becomes even more finely grained when it is the uses that change, not the physical (or legal-spatial) entity.

We have some strategies for modeling date uncertainty and evolution, some of which already have built-in software support. However, there are still some outstanding pain points, particularly when it comes to name changes.

If I haven’t scared you away already, I’d encourage you to start a discussion on the forum or get in touch with the advisory group so we can explore further. Thank you!

Welcome to OpenHistoricalMap, Benjamin, and thank you for your insightful comments!

You point to a natural tension in historical mapmaking and to some extent in the sort of modern mapmaking that our friends at OpenStreetMap do as well. For me, as a resident of California, I look to the fact that California was once portrayed on European maps as an island – OHM will never show California as an island during that time period, no matter how many contemporary sources say otherwise. As we try to discern the truth, we will necessarily rely on prior art, but we’re fundamentally a work of synthesis, bringing in the best of a variety of sources, including those that say California is not an island and Alexander Street never opened.

For something physical like a landmass or street, at least there’s an objective truth, but we also sometimes grapple with more abstract features. The difference between de jure and de facto boundaries is already fraught enough in OpenStreetMap, let alone OHM, where we have to contend with sometimes outlandish claims made by colonial powers before they even knew what that side of the world looked like. I think the best we can do in many cases is to communicate any caveats about what we show or omit.

Regarding the time slider, 1825 is just a default. We would set the start much earlier, but it would make it more difficult to adjust the date granularly by day. You can adjust the slider’s range using the row of controls immediately above the blue bar. We’ve seen a lot of people overlook these controls; the whole time slider is in need of an overhaul, which could include some improvements to make the range more dynamic.

Many years ago, I had to go through this part of town deleting lots of nonexistent streets that ostensibly climbed up the hill.

Deleting them from OSM, that is. Hard to delete something from OHM that hasn’t been mapped yet. 😛

Without looking, I’m going to venture a guess that Alexander Street is in TIGER too. Many years ago, I had to go through this part of town deleting lots of nonexistent streets that ostensibly climbed up the hill. Maybe this was one of them, or maybe someone got to it before me.

Did you know Hamilton County publishes a substantial dataset of paper streets and vacated streets in the public domain? An import of highway=proposed and not:highway=* ways? Peak OHM!

The forum thread for this project has a link to the spreadsheet, in case anyone wants to see how it’s done.