this post was submitted on 15 Feb 2024

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How do you add buildings when the map is crooked? (lemmy.dbzer0.com)

submitted 9 months ago by Tippon@lemmy.dbzer0.com to c/openstreetmap@lemmy.ml

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Sorry, crooked isn't the best word, but I can't think of a better one.

I'm still quite new to OSM, and I want to start adding the buildings in my town. When I open the edit option though, the map overlay is at an angle. It's not a massive amount, but it's enough that you can see one sometimes two sides of most buildings, so the roof isn't aligned straight down, if that makes sense?

I live near Aberdare in South Wales, and you can see that where someone has added some buildings in the town centre at some point, they're now not aligned with the map overlay:

https://www.openstreetmap.org/edit#map=20/51.71312/-3.44499

Do I draw around the roof that I can see on the map? Do I edit the existing buildings so that they line up with the overlay? I'm not sure what the best course of action is for something like this.

Thanks in advance :)

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[–] GravitySpoiled@lemmy.ml 12 points 9 months ago* (last edited 9 months ago) (3 children)

If you plan to add many buildings, I suggest using josm instead of id. It's a much smoother experience.

Usually, you take care of the "imagery offset" in the beginning of a mapping session. For this you use gpx tracks to align the different map layers. You can also use other shapes you already aligned properly in the past. With newer or different imagery it can happen that the imagery is slightly off.

For a building, you usually use the roof and move the final shape to a corner which is visible on the map. You may have to adjust things if the roof has a different shape than the building.

Yes, you move all buildings if all of them are off. This is easier done in josm than in id. You can also align the map to all the other buildings and hope that some day someone else will align it. Hint: this will be you, but in the future.

[–] governorkeagan@lemdro.id 10 points 9 months ago (1 children)

Using “imagery offset” in JOSM made my life so much easier when I started adding large amounts of buildings.

There’s a learning curve to it (JOSM) but it’s well worth it.

[–] GravitySpoiled@lemmy.ml 7 points 9 months ago

This reminds me of https://rapideditor.org/ . It's made by facebook but it may be useful for certain areas.

[–] infeeeee@lemm.ee 3 points 9 months ago

For drawing buildings in JOSM the Building Tools plugin is godsent: https://wiki.openstreetmap.org/wiki/JOSM/Plugins/BuildingsTools

[–] Tippon@lemmy.dbzer0.com 1 points 9 months ago

I'll give that a try, thanks :)

[–] yo_scottie_oh@lemmy.ml 5 points 9 months ago (1 children)

Other commenters have left some good advice already, just wanted to chime and say the word you’re looking for is “tilt” (when the image is not straight down, causing the sides of buildings to be visible).

[–] Tippon@lemmy.dbzer0.com 1 points 8 months ago

Thank you, the word just wouldn't come to me :)

[–] InsertUser@en.osm.town 2 points 9 months ago (1 children)

@Tippon Imagery often needs to be re-aligned to match up with local traces. The wiki has some guidance on the general "Using Aerial imagery" pages and on handling off axis imagery on the page for roof modelling.

https://wiki.openstreetmap.org/wiki/Using_aerial_imagery
https://wiki.openstreetmap.org/wiki/Roof_modelling

[–] Tippon@lemmy.dbzer0.com 1 points 9 months ago

Brilliant, thank you :)

[–] achadwick@urbanists.social 1 points 9 months ago (1 children)

@Tippon you can use https://osmuk.org/cadastral-parcels/ as an overlay and work off of property boundaries. It's as close to perfect as you can really get using public layers, and it's becoming a bit of a standard round my patch for realignment jobs.

I use it for aligning Bing layers to cope with the tilt, and it's still handy as an overlay after that for jobs like chopping terrace rows into individual houses

[–] Tippon@lemmy.dbzer0.com 1 points 8 months ago

Thank you, I'll give it a try :)