topic Re: Calculating standard deviations of elevation within specific buffers in ArcGIS Spatial Analyst Questions

Calculating standard deviations of elevation within specific buffers

Jessica_Fort — Wed, 23 Sep 2015 20:39:58 GMT

I'm fairly new to GIS and I haven't been able to find much on this specific topic in the ESRI community.

I would like to be able to calculate a "Terrain Ruggedness" index for each one of my sites in my study area and found a couple different suggestions, but I think calculating the standard deviation of elevation would give me useful values. The problem is I can't find how to calculate this within specific buffers. For example, I have made a TIN from a contour shapefile around my sites (Figure 1; edited with river shapefile) and then converted that to a Raster shapefile (Figure 2). I've made 500m buffers around each site and would like to calculate the standard deviation of elevation within those buffers for each site. OR really any kind of value that could measure "terrain ruggedness" within each buffer.

Are there any suggestions on how to do this?

Thanks!

Jess

Figure 1. TIN

Figure 2. Raster

Re: Calculating standard deviations of elevation within specific buffers

DanPatterson_Retired — Wed, 23 Sep 2015 21:13:02 GMT

Since you marked this question "Assumed Answered" you might wish to share on how you did it should anyone come across this thread in a search for similar answers...otherwise this post will be ignored by many since it looks like you don't need any help ... which may or may not be the case

Re: Calculating standard deviations of elevation within specific buffers

Jessica_Fort — Thu, 24 Sep 2015 14:33:24 GMT

Thanks Dan. I actually accidentally marked the question "Assumed Answered" and now can't figure out how to erase or edit it. So I will repost and hope that people ignore this first one. Thanks!

Re: Calculating standard deviations of elevation within specific buffers

SteveKopp — Thu, 24 Sep 2015 16:33:42 GMT

Jessica - if what you want is simply the standard deviation of a DEM within a neighborhood (radius) you can simply use the Focal Statistics tool with the default circular neighborhood and radius of the distance you want, and the STD option.

Or if you want a terrain ruggedness index tool that already exists, there is a free toolbox for Geomorphometry and Gradient Metrics created by Jeff Evans which includes a Roughness tool that is based upon the Riley et al 1999 Terrain Ruggedness Index approach.

http://evansmurphy.wix.com/evansspatial#!arcgis-gradient-metrics-toolbox/crro

Steve

Re: Calculating standard deviations of elevation within specific buffers

Jessica_Fort — Thu, 24 Sep 2015 20:44:47 GMT

Thank you, I think I figured it out!

Re: Calculating standard deviations of elevation within specific buffers

GaiusWilson — Sun, 21 Jul 2019 14:32:10 GMT

So do you actually have an answer to this question? If so, can you please share it? I'm trying to calculate the TRI from the standard deviation of elevation but with a 1 km distance from each cell. Where and how do I specify the 1 km? Thanks.