[Talk-GB] NLS historical OS plans for grid square TQ

[Adrian]

I have been in touch with Chris Fleet, the curator of maps at the National Library of Scotland. He has confirmed that the historical Ordnance Survey maps of London and south-east England at 1:1250 and 1:2500 are now available for use in OSM. I have added an entry for these maps in the wiki [1]. I have added the maps to the list of imagery sources used by JOSM (because it was straightforward to do). I have not added them to the Editor Layer Index used by iD etc. [2], because I don't have a Github account and I don't know how to do a pull request.

Note that these maps need to be aligned, using the OSMUK Cadastral Parcels. This is because the NLS has used the Helmert transformation to convert from British National Grid projection to Web Mercator projection. [There is another factor causing misalignment, although it doesn't affect London and south-east England. So, using the look-up table transformation would not be a complete solution to misalignment. This factor is that in some places the OS have *moved their grid lines* by a few metres since the maps were printed. Locations affected include the Scilly Isles, Stornoway and Oban. Maps of Stornoway and Oban are already available from the NLS.]

Chris Fleet also proposed a revamp of the wiki page [1]. I don't think he is aware of the way the calling-up of imagery layers in OSM editors has been simplified/automated.

On 23 December 2022 at 12:17, Fleet, Christopher wrote:

... This page, though is very dated, and doesn't include a range of other georeferenced maps which may also be useful to OSMers. For example, in the last year, we have put online over 400 OS Town Plans of English and Welsh towns at https://maps.nls.uk/os/townplans-england/ at 1:1500-1:1,056 scales which are not listed, and we've just added potentially useful air photos for England and Wales too https://maps.nls.uk/additions/#134.

I was wondering what you would feel about a wider revamp of that NLS OSM wiki page which pointed to the way that XYZ URLs of all the NLS georeferenced layers can be found following the guide at https://maps.nls.uk/guides/georeferencing/layers-urls/, and then following the guide at https://maps.nls.uk/guides/georeferencing/osm/ for how to bring them into OSM. This would mean that the latest correct URLs for our georeferenced layers were always used, and OSMers could access all the NLS georeferenced layers.

Would be interested in your thoughts on this.
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I don't know the history of how the current wiki page was arrived at. And I don't know how the NLS entries in the lists of imagery sources were compiled. So I'm probably not the right person to liaise with Chris Fleet over this. Would someone like to take it up please? (The email address is on the wiki page.)

[1] https://wiki.openstreetmap.org/wiki/National_Library_of_Scotland
[2] https://github.com/osmlab/editor-layer-index