[GIS] Raster to vector conversion

openstreetmappostgisvectorization

I have a bunch of raster maps from a general plan of a city.

Examples:

I need to vectorize them such that I can store all elements (lines, polygons, points) of the map listed in the legend in a database like PostGIS such that I can

  • find all elements of a master plan, which affect a certain region on the map (e. g. if I have a house at location X and the government wants to build a road in the same place, I want to notice it) and
  • compare two versions of a master plan by running database queries.

The ultimate purpose is to bring the data contained in these maps into a format that can be understood by non-technical people – inhabitants of the city so that they can express agreement or disagreement with the general plan.

One obvious approach is to simply lay raster map over a vector map of the region (there is a vector map of that city in OSM) and manually transfer the lines from raster to vector form.

  1. What tools (preferably open source) can I use to vectorize the maps manually and save the data in PostGIS?
  2. Are there any alternatives, which are faster? Can this process be automated (fully or partially) using open source or inexpensive commercial software?

Update 18.01.2013: FYI: I asked the copyright holder (city administration) of the maps to provide them in vector format. I'll wait for their answer and then decide on further actions.

Update 27.01.2013:

Today I made a first experiment in georeferencing for these maps.

Inputs:

  1. OpenStreetMap map
  2. Raster map

Process: You can see how I do georeferencing in this video.

Results:

  1. GCP points for both maps
  2. Modified raster map

I have following questions:

  1. How many points do I need to enter in order to have good enough quality of the mapping? Are there any rules of thumb for that?
  2. What can I do to improve the quality of the mapping (remove mapping defects shown below) ?

Sample mapping defect #1

Mapping defect #1

Sample mapping defect #2

Mapping defect #2

Best Answer

I advise you could use Wintopo, sir :)

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