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Following the query;

Cannot extract the WMS tiles to arbitrary GIS format

where I asked about a possibility to get the WMS layer to QGIS or get the layer in some versatile vector GIS format.

Now I would like to ask about the possibility of vectorizing the raster map by color.

enter image description here

As you can see, I have the infrastructure, which is entirely black. It's distinguished well from the map canvas underneath.

Is it possible to vectorize only these layers at some point? Make the colored vectorization? I want only the structure, but I don't need the map at all.

Something analog to "Trace Bitmap" tool in Inkscape?

https://www.youtube.com/watch?v=E7HwLTQu2FI&ab_channel=TJFREE

Geographos
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  • Screenshot everything, merge the images, then use the raster calculator to create a mask, then convert the mask to vector data. And no, the data wont look great. – Erik Jul 20 '21 at 13:27
  • What do you mean by "screenshot everything?" and how to make the mask in QGIS? – Geographos Jul 20 '21 at 13:32
  • Screenshot the whole area of interest, or rather export it to georeferenced images. – Erik Jul 20 '21 at 13:54
  • you know there is a Vector Tile Service (VTS) for that data right? https://osdatahub.os.uk/docs/vts/technicalSpecification – Mapperz Jul 20 '21 at 15:09

1 Answers1

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I had some fun with your image:

  1. Use raster calculator to recalculate the image to 1 or 0:

(("xSTNz@1"+"xSTNz@2"+"xSTNz@3")<75)*1 + (("xSTNz@1"+"xSTNz@2"+"xSTNz@3")>74)*0 Where sum of the bands are below 75 (almost black) give them the value 1, else 0 enter image description here enter image description here

  1. Use Warp to set no data value to 0: enter image description here
  2. Raster pixels to polygons, only the no no-data (1) gets vectorized:

enter image description here

Still very raw data, but in vector format. I would then try Dissolve, find centerline etc...

BERA
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