I am adding terraced housing to many streets in my part of London where they are either missing, or just indicated as a single long rectangular area.
I am using Terracer and adding address numbers.
My question: Most of these houses have been modified in some way, especially rear extensions of various shapes and sizes. Using the Bing satellite imagery as guide, I have been using the Extrude tool to represent the house outlines reasonably accurately. It doesn’t take too much extra time, but I’m wondering if this is the right idea or goes against OSM conventions. It does make the map look messier, for example it causes the numbers to no longer line up.
Here is an example where I’ve done this (south terrace), and where I haven’t (north terrace):
If the view from above is messy in reality it is fair enogh that the mapped outlines look messy as well. I alway map what I can see in reality, not what was shown in the construction plans.
You shouldn’t worry about what it looks like on the map, or rather, on this particular map (Carto, I assume?). Other renderers may have more sophisticated algorithms to place house numbers, or may not show them at all.
This practice is called ‘mapping for the renderer’, and should be avoided.
I too am working through converting terraces to individual buildings in London. Where the aerial imagery is clear, I try to add the most accurate possible outline.
My JOSM workflow:-
Align the terrace to the Cadastral.
Use the Terracer plugin to convert the block to individual (uniform) houses.
Use the Extrude tool to “pull out” the rear extention.
Check the houses are still connected.
Draw on a rough back wall/fence for the permeter of the full range of gardens.
“Fill” the garden perimeter using the Balloon tool. That results in a single closed way for the gardens. If the houses weren’t all connected right, the shape will have kinks and self-overlaps to fix (or undo and try again).
I set the garden area to to leisure=garden; access=no; garden:type=residential.
If there were any address nodes (e.g. on interpolation ways); they can be merged into the correct house using Replace Geometry, Ctrl+Shift+G.
“Missing” housenumbers can sometimes be found in the ‘Old / Historic’ maps backgrounds. But there’s no substitute for a visit in person.
Postcodes can be added from the permitted Code-Point Open source - I only add these where they coincide with a particular house.
Sit back and wait (a few days) for rskedgell_import to come along and add the UPRNs to all the houses that lie within the relevant cadastral boundary.
(Instead of 2 and 3, I sometimes use the extruder tool to make the whole terrace the correct shape, and then divide it into houses using the split tool; then use the housenumber tagging tool to run through and add all the address tagging.)
Thanks for the excellent guidance and example, @spiregrain.
I had never heard of cadastral parcels prior to this thread. I assume it involves adding this overlay to the map in addition to the satellite imagery? Cadastral Parcels – OpenStreetMap UK
The satellite imagery - I use Bing - is pretty blurry so the terrace extensions can involve some guesswork. Sometimes a paved patio could look like a roof, sometimes you can’t tell a roof from an awning, etc. But I try my best without making the outlines over-complex. I aim for @spiregrain’s level of detail. Here is an area where I’m working: OpenStreetMap [I’m noticing strange shape doubling now in that area, I’m wondering if that’s related to a conflict I struggled to resolve.]
Some notes / questions from your workflow:
I have been ignoring postcodes so far.
You say you’re adding back walls / fences, but I don’t see them. I only see the gardens. Does the Balloon tool remove the fences when creating the gardens?
I notice you are adding all pavements as footpaths. Is that the OSM norm for cities?
When using the extruder tool, I always end up with the adjacent extension nodes on top of, but separate from each other, and I have to Ctrl-drag each of them to snap them together. Is there a more efficient way to do this?
Is there a video or tutorial anywhere explaining the Replace Geometry tool?
Yup - that’s the Cadastrals, they are the best available source of alignments (except for getting your own high-grade GPS receiver and hanging around on street corners with it). In most areas it’ll give you a bright blue line round the edge of each current (and some historic) property boundaries. You can align aerial imagery to it (e.g. match fences to the blue lines), and be fairly sure that you’re ‘tracing’ in the right location however misaligned or paralaxed the imagery is.
Well worth experimenting with the other imagery sources, just in case there happens to be one better.
I can see the shape doubling too - should be easy to delete the dupes.
Fair enough re: postcodes. It’s not necessary. There is a postcodes layer you can turn on that gives the ‘centroid’ of each postcode. It should be safe to set that as the postcode for the single building that is nearest to that point. Doing more than that is guesswork. (Plus rskedgell_import will do the rest wherever possible.) If you want to get into postcodes, this is a good source: Postcode Stats (W6) | Robert Whittaker's OpenStreetMap Stuff
I should have said - I add the fencelines temporarily so the ‘balloon fill’ does the right thing. It’s very difficult to tell a fence from a wall in aerial images, so I just don’t bother. If you look in suburban Edinburgh, you should be able to find areas with individual fences and gardens.
I don’t routinely add separate footpaths - it can be useful, but it’s more often counter-productive. We’ve had some visitors from Big Tech adding footpaths lately, perhaps those are the ones you’ve found? Where they are added it’s important to link them to streets and crossings - lots of extra work.
You can join nodes by clicking and pressing m to merge and/or j to join. Should be quicker than dragging; but I agree the default behaviour of the extrude tool sometimes leaves stuff to be cleared up. If it’s too annoying, try the ‘alternative’ method of getting the terrace shape correct first, then splitting (in brackets at the end of the above).
Replace geometry - I’ve not seen such a video, but you can select a node (e.g. an address node); additionally select a closed way (e.g. a new house), make sure it’s just those two objects, and press Ctrl+Shift+G. The tagging on the point, and some of the history of the point (?) is transferred to the closed way, and the point is removed. (You’ll need to have the UtilsPlugin2 installed, but all decent folk do).
Are the cadastral parcels used for visual alignment when drawing, or will the drawing tools literally snap to them?
I use the Split tool for some terraces that have gaps in them, otherwise Terracer gets the sizes wrong. (On Fulham’s ‘alphabet streets’ they seem to have been constructed in groups of 6.) I might use it more often.
Replace geometry - still not quite sure where I’d use that. Where do address nodes come from that are separate from a house?
Temporary fences: noted
Cleaned up the dupes
What do you do about back garden sheds? I’ve been ignoring these apart from the largest freestanding garages
Building type: so far I’ve either ignored this property or used Residential Building. Would it be better for all of these to be ‘House’?
You’ll need to manually move the aerial images to match. Here’s a tutorial that covers aligning backgrounds to GPS traces - LearnOSM
VG
If there are no address nodes already, no problem! Some of the streets in my manor have this sort of thing. It’s be easy to delete these nodes once the houses are in place and tagged. Replace Geometry (as far as possible) makes the house object into a ‘new version’ of the address object so that the history is preserved. Probably not important, but it’ll tell posterity (if it cares) that the old node and new house are the ‘same thing’. In principle, it’s better to update an object than to delete and replace it. Replace Geometry makes that a bit easier.
I tend to ignore mid-terrace sheds, but I sometimes add sheds / garages that face onto the roads - these might eventually benefit from driveways.
I’d say they should be houses. If you can tell that they’ve been converted into apartments, then it might be a case for building=house AND building:use=apartments. If they are purpose-built apartment blocks, then just building=apartments. Some also add house= terraced|detached|etc.
