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Are there any software packages/solutions that allow me to simulate the movement of sun or direction of sunlight over a period of time (e.g. 24 hours)?

My purpose is to determine the regions cast in shadow for different times of day, when used in combination with a DEM.

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2 Answers 2

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There are some tools that will meet your needs:

  1. GRASS GIS r.sunmask tool - which will perform fully automatic shadow cast computation based on DEM. It is based on SOLPOS 2.0 sun position algorithm. Please refer to detailed description on GRASS manual webpage.
  2. SAGA-GIS Analytical Hillshading module - this tool will also derive shadow cast but it's not as automatic as GRASS one. Apart from delivering DEM to SAGA you will also need to input detailed sun position information. To do so: extract WGS84 coordinates of DEM center point, use this solar position calculator pass computed solar azimuth and elevation angle as inputs in Analytical Hillshading module. Attention: only northern hemisphere positions are supported.
  3. ESRI's ArcGIS Sun Shadow Volume (3d Analyst) - as far as I remember this tool is also provided with sun position calculation algorithm. Haven't been using this one in a while so I will refer to official instructions.

Using those enlisted modules you can create rasters for any time interval an then create an animation if needed.

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  • A faster algorithm is GRASS GIS' r.sun module, filtering out incidence angle = 0. See also here: grass.osgeo.org/grass70/manuals/r.sun.html#shadow-maps
    – markusN
    Commented Mar 20, 2015 at 19:34
  • @jzol thanks for the various alternatives to simulate sun movement. I'm particular interested in the ArcGIS actually, although I cant find much information on it. What does Sun shadow volume mean?
    – Corse
    Commented Mar 23, 2015 at 4:16
  • Are these also able to compute the amount of time that a particular point is in shadow/sunlight?
    – Corse
    Commented Mar 23, 2015 at 4:18
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You can use gdaldem. I suggest you to have a look on http://blog.thematicmapping.org/2012/06/creating-hillshades-with-gdaldem.html You can can produce hillshade for all the azimut and elevation angles and then combine them together.

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  • Hillshading won't help for this application, since it just takes the aspect of the local terrain into account, but doesn't simulate the casting of shadows from other terrain features. For instance, in the afternoon the west facing slope of a steep valley could be illuminated according to the hillshading algorithm, but in reality it would be shaded by the opposite hill.
    – Jake
    Commented Mar 20, 2015 at 14:12
  • @jake oh i see, what tools will be able to account for shadows casted by adjacent hills?
    – Corse
    Commented Mar 23, 2015 at 4:35

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