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having a binary raster map of pixels of interest, a road network, and a target point, my goal is to get a raster map with network pixels having as value the number of pixels of interest they allow to reach.

Would you know how i could use GRASS GIS tools to perform this?

The steps i foresee are:

  • rasterize the network using v.to.rast
  • compute pixels of interest distance to the network using r.grow.distance,
  • compute a direction map with r.cost,
  • add the target point to the network with v.net operation=connect,
  • alter network lines directions toward the target,
  • rasterize the network again using v.to.rast use=dir,
  • overwrite the direction map with network direction pixels with r.mapcalc,
  • build a directed graph from direction map,
  • set a value of 1 to nodes that are on pixels of interest,
  • perform a graph traversal toward the target, cumulating nodes values.

By now, i still don't know how to revert lines directions or build the graph.

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To revert line direction you can go with v.edit and the flip option.

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Using r.watershed -s with cells of interest provided as flow on a distance to network raster map (from r.grow.distance), i obtained the accumulation map answering our issues.

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