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I'm trying to shift point coordinates "upwards" based on a slope/aspect raster that I have computed beforehand. Working preferably with QGIS, but other means (i.e. R/ArcGIS [Standard/Pro]) are also possible.

I've looked for transformations, but haven't figured out how I'd make it dependent on attributes in general (~ underlying raster cells, specifically slope/aspect in my case).

I.e. I have a point dataset with points "red" and "blue" (black circle in image) from which I'd like to generate a new point dataset (green circle in image) based on slope/aspect.

red:

  • slope: 45° (steep => larger shift)
  • aspect: 0° (facing north => moving south (180°))

blue:

  • slope: 10° (shallow => minor shift)
  • aspect: 90° facing east => moving west (270°)

sketch displaying the point shift I'm trying to achieve

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  • 1
    Yeah, first step would be adding slope and direction as attributes (add raster value to points), then you can go on.
    – Erik
    May 3 at 8:40
  • @Erik thanks, getting the raster values as attributes is not the problem though. generating the new coordinates based on them I haven't figured out yet
    – Honeybear
    May 3 at 8:48
  • @BERA no, I'd rather use continous values.
    – Honeybear
    May 3 at 8:48
  • Can you add a screenshot showing the attribute table
    – BERA
    May 3 at 8:55
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    And provide a logic which the shift should follow? Also: Should the actual geometry be moved, or does a changed symbology suffice?
    – Erik
    May 3 at 9:00

1 Answer 1

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Use QGIS expressions with Geometry Generator (for visualization purpose only) or Geometry by Expression (for actual geometries) - see here for more details about both options.

Use this expression, replacing slope and aspect with the names of your attribute fields:

project( 
    $geometry, 
    slope,
    radians (180+aspect)
)

Red points shifted to the blue destination, including a coeficient of 2000 on line 3 for the distance:

enter image description here

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    This is perfect, I'd give +2 if I could for even providing a solution for visualization only. That allows to quickly experiment with the coefficient to scale the distance of the shift without generating actual geometries on each iteration! Thank you.
    – Honeybear
    May 5 at 14:45

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