Florian Lohoff

To the professional #GIS people. Is there a definition for #Hillshading from where you suppose to assume the "sun" is coming?

The DTM Hillshading for Northrhine-Westfalia is rendered with Sun from North which is so confusing when looking at only the Hillshading layer.

Aug 21, 2024 at 8:01amWeb
Show threadRihards OlupsAug 21, 2024

@flohoff That reminds me of this article: https://ramblemaps.com/why-does-sunlight-come-from-north

"Why Does The Sunlight Come From The North In Shaded Relief Maps?"

Why Does The Sunlight Come From The North In Shaded Relief Maps?

If you've got a sharp eye and a knack for details, you might have noticed the sun coming from an unrealistic angle in most shaded relief maps: the north. In this article we explain why.

Show threadFlorian LohoffAug 21, 2024
@richlv Thats what i was looking for - Still everytime i open the Hillshade layer to find stuff in the Woods its simply confusing. And i cant adapt it seems.
Show threadDetlev Zundel [Team Human]Aug 21, 2024
@richlv @flohoff Thanks for the link!
Show threadGuillaume RischardAug 21, 2024

@flohoff gdal multidirectional hillshading uses “a combination of hillshading illuminated from 225 deg, 270 deg, 315 deg, and 360 deg azimuth” and is what I used at https://lidar-hillshade-2019.openstreetmap.lu

https://gdal.org/programs/gdaldem.html

OpenStreetMap - Lidar Hillshade 2019

Show threadJavier Jimenez ShawAug 21, 2024

@flohoff somehow we are used to scenes where the light is coming from the top, so shadows are cast to the bottom. Like the illumination in your table when you are writing.

Northern the tropic of Cancer, 23deg north, the sun is always in the south.

There was an article (that I cannot find now) telling that a US agency wanted to be more "correct" in the hillshaing of their maps putting the sun in the south. They had to change back to the north because people were confused.