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I would like to create a road (polyline) starting from a point, with a specified slope, until reaching the top of a hill (or going out of the DTM Raster).

The dowstream slope of the DTM must always be on the same side of the created polyligne to avoid hairpins.

I am working with qgis, arcgis-10.1, python, ...

I found some developments but that work with Autocad :

http://files.carlsonsw.com/mirror/manuals/old/dtm.pdf

https://www.youtube.com/watch?v=t6VAKWSD-7o

I have almost the same need that Craig :

3D Polyline by Slope on Surface

Somebody can tell me what would be the best method ?

Or is there already someting that could do that ?

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laurent.descroix
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1 Answers1

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You can use GRASS in QGIS as described here. Just create a slope layer then, using the raster calculator, make a new layer of a range of acceptable slope angles. You can then run the r.cost and. r.drain tools as mentioned in the other post and then polygonise the r.drain output and you've got your road.
Remember that when you run the r.drain tool that you select your end point at the top of the hill as it is a regressive tool. Otherwise you'll get an output of a single dot and you wondering where the rest of it is.

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Knightshound
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