Units for curvature in whiteboxtools

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Zachary Brecheisen

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May 17, 2021, 11:18:16 AMMay 17
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Hello, everyone! I have read that units of measure for curvature metrics should be degrees (or radians) per some unit of length. Is that the case for the whiteboxtools different curvature tool outputs? Therefore they would be degrees*100/projected units? Would DEM pixel resolution have an effect on the units reported? I apologize if these questions have obvious answers.

Whitebox Geospatial

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May 17, 2021, 3:33:20 PMMay 17
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Hi Zachary,

Thanks for your question.

In WhiteboxTools, the output for all curvature tools report curvature in degrees multiplied by 100 for easier interpretation. The reasoning for this can be found in the following reference:

Gallant, J. C., and J. P. Wilson, 2000, Primary topographic attributes, in Terrain Analysis: Principles and Applications, edited by J. P. Wilson and J. C. Gallant pp. 51-86, John Wiley, Hoboken, N.J.

While doing this allows for easier interpretation, it is can also exaggerate curvature values. It is a good rule of thumb to center the maximum and minimum raster values to something a reduced range and centered on zero (i.e., -100 to 100, -10 to 10, -1 to 1).

Pixel resolution should not have an impact on the units reported. However, if the vertical and horizontal units are not the same in the input DEM, you will have to make use of the Z Conversion Factor(--zfactor) parameter. I have attached a link to the ProfileCurvature Tool in WhiteboxTools for reference (https://jblindsay.github.io/wbt_book/available_tools/geomorphometric_analysis.html#ProfileCurvature)

Hopefully this helps to answer your question.

Best

Whitebox Geospatial 

Zachary Brecheisen

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May 17, 2021, 3:54:46 PMMay 17
to Whitebox Geospatial, WhiteboxTools
Hi, thank you for the reply. So the units are solely in degrees? I have gotten push back from journal peer reviewers and editors that curvature units must be in degrees over some length unit.  

Hasta luego, 

Zachary Brecheisen, PhD

 

Post-Doctoral Researcher

Purdue University, Department of Agronomy

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