Steve on Image Processing

March 30th, 2007

Upslope area - Introduction

 A long time ago, blog reader Brendon asked me if I knew of a way to compute something called upslope area in MATLAB. I responded that I had never heard of that before. Brendan explained that it was a measurement related to digital elevation models (DEMs). The upslope area of a point (pixel) is the total area on the terrain above that point that drains through it.

That sounded like an interesting algorithm development problem to me, so I did a little research and found some suitable-looking algorithms. I even partially implemented one. But I never did find the time to work out all the different pieces, so I never got around to writing about it here.

I finally decided recently that I just need to dive in and try it. And I'm going to do it in front of you readers. I've picked a paper that looks promising (by David Tarboton of the Utah Water Research Laboratory, Utah State University), and for the next few weeks I'm going to try to turn the methods described in this paper into a working MATLAB implementation.

We're going to get into flow direction computations, how to deal with plateaus, and maybe (if I'm guessing right) even some sparse linear algebra.

Next up: the D∞ flow direction method.

By Steve Eddins

07:00 UTC | Posted in Upslope area | Permalink |

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2 Responses to “Upslope area - Introduction”

  1. Qi Chen replied on April 1st, 2007 at 11:11 UTC :

    look forward to it

  2. Wolfgang Schwanghart replied on April 2nd, 2007 at 12:56 UTC :

    Steve,
    I am curious about your results. I have just submitted a flow accumulation and flow direction algorithm to the FEX, that routes across flats. I am very glad to hear that Digital Elevation Model analysis is pushed forward at Mathworks. Geoscientists will be delighted :-)

    Best regards,
    Wolfgang

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Steve Eddins manages the Image & Geospatial development team at The MathWorks and coauthored Digital Image Processing Using MATLAB. He writes here about image processing concepts, algorithm implementations, and MATLAB.

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