Extracting Slope angle from Colour Dem

I'm sure there is a geoprocessing tool or plugin for QGIS that will do this, and I'll explore that next, but thought I should ask in case it can be done easily on MME. Is there a process, tool, etc. for extracting slope angle (degree or %) from the generated DEM file? For example, one draws a polygon around a small continuous section of a slope or clicks on a point on a slope, and like volume calculations, a slope angle value is calculated?

This would be a very handy tool. I'm sure it will be a more cumbersome, time-consuming process in Q or Arc.

Chris Campagnaro 25 de agosto de 2021 18:30

Comentário oficial

If you are working with the actual DEM file itself you would just want to use a QGIS tool to do it. Do that like this:

https://docs.qgis.org/2.14/en/docs/training_manual/rasters/terrain_analysis.html

The way to do it in the browser would be do draw a line of a known length.

Then get the elevation of the two endpoints.

Elev Diff = -174.3 - -238.7 = 64.4 ft (bad example because this map had negative elevation values due to not using a ground reference image)

Slope = Rise/Run = 64.4 / 1231.1 = .0523 slope = 5.2% grade

Zane 25 de agosto de 2021 18:52

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2 comentários

Thx Zane,

I did it both ways, in-browser S=R/R is the 'quickstep' I was looking for, probably should have tried harder. Q terrain analysis definitely better if you want to save an entire layer of slope values.

Chris Campagnaro 25 de agosto de 2021 20:43 0 votos