Planform & Profile Curvature

[Jeran Farley]

When using planform or profile curvature, if I try to zoom any closer than 1:6,000 it gets blurry.  Is this normal, or are we supposed to be able to zoom in closer?

[Shannon Wing Belmont]

Jeran, the outputs should have the same resolution as the original raster... Maybe something got messed up when the pyramids were built.

When I get up to school I'll run it myself and see if I can offer some feedback that's more helpful...

On Wed, Apr 3, 2013 at 6:52 AM, Jeran Farley <jeran...@yahoo.com> wrote:

When using planform or profile curvature, if I try to zoom any closer than 1:6,000 it gets blurry.  Is this normal, or are we supposed to be able to zoom in closer?

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Shannon Belmont

Quinney College of Natural Resources
Utah State University
5210 Old Main Hill
Logan, UT 84322-5210

[Alice]

Hi all,

 

My curvature rasters look ok, but when I calculate zonal stats, my standard deviation seems really high compared to the means. I have a profile curvature mean of .0688 and a standard deviation of 25.36. Max and min are 856 and -831. The planform numbers are similar. I tried running it again, with a pit-filled DEM, and the results are pretty similar. The ESRI blog about curvature was great, but didn't include any numbers, and I can't seem to find anyone talking about what is "normal" for curvature. Did anyone else get numbers like this? Thanks for any help.

 

Alice

[Shannon Wing Belmont]

Alice, Great observations and troubleshooting.

You really won't find "standard numbers" for curvature because they are so dependent on the terrain.

When I first ran curvature for the Ogden watershed I was shocked (800 - -800!) and reran because I figured I'd done something wrong, too.

I had been used to working on the Big Cottonwood Canyon, where the curvature values are closer to 50 - -50.  And all my grad research was in Minnesota where typical steep features (ravines) that I worked with had curvatures of 14 - -14. 

So these values just indicate 1) that the Ogden watershed you are evaluating has some crazy slope derivatives going on, and 2) that 2m data produces more extreme results than if you were working with 10 or 30m data. 

You wouldn't necessarily know any of this unless you had the opportunity to compare curvature for multiple datasets for multiple watersheds...

But this is the beauty of zonal statistics, that it allows you to compare surface stats for multiple features on the landscape (ravine features, canyons, watersheds, city limits, etc.)

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[Alice de Anguera]

Thanks - good to know!

Alice

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From: Shannon Wing Belmont <swb....@gmail.com>
To: usu-nr-...@googlegroups.com
Sent: Monday, April 15, 2013 11:00 AM
Subject: Re: Planform & Profile Curvature