topic Re: How to measure ruggedness by polygon in ArcGIS Pro Questions

How to measure ruggedness by polygon

Mikhail — Sat, 04 Mar 2023 03:07:17 GMT

I work with the map of the UK divided into about 5,000 polygons. I'd like to measure the ruggedness of terrain by a polygon with TRI or any other index but can't find the right tool for this task. Could you recommend a solution?

Re: How to measure ruggedness by polygon

swfbtucs — Sat, 04 Mar 2023 03:25:45 GMT

I was glad to see your question as I did not know of TRI and I have a use for it. A little googling found this: https://community.esri.com/t5/water-resources-blog/terrain-ruggedness-index-tri-and-vector-ruggedness/ba-p/884340

Re: How to measure ruggedness by polygon

Mikhail — Sat, 04 Mar 2023 03:46:41 GMT

Thank you, I saw this post too. The trouble is I can't find anything like Arc Hydro functions in my system. Can you see them in yours?

Re: How to measure ruggedness by polygon

Omar_A — Sat, 04 Mar 2023 03:48:08 GMT

Hi Mikhail,

To calculate the TRI in ArcGIS, try this workflow:

You need a (DEM). Try open-source data websites like the Ordnance Survey, the European Space Agency, and the US Geological Survey.
Convert your polygons into raster format using the Polygon to Raster tool, and choose an appropriate raster cell size that works for your analysis.
Extract by Mask tool to clip the DEM raster to the extent of your polygon raster.
Calculate the TRI for each polygon using the Ruggedness Index (TRI) tool in ArcGIS Spatial Analyst extension. Have a look at the tool's documentation.
You can then export the TRI values as a table or join them to your original polygon dataset for further analysis.

Other software packages that calculate the TRI include QGIS, GRASS GIS, and SAGA GIS. The specific steps for calculating the TRI may differ slightly between these software packages, but the general workflow should be similar.

Thanks,

Re: How to measure ruggedness by polygon

swfbtucs — Sat, 04 Mar 2023 03:59:40 GMT

No, now that you ask. Interesting. There is nothing referring to hydro in geoprocessing.
Ok, here we go: https://www.esri.com/en-us/industries/water-resources/arc-hydro/downloads#arc-hydro-for-arcgis-pro

Re: How to measure ruggedness by polygon

Mikhail — Sat, 04 Mar 2023 11:05:20 GMT

Hi Omar,

Thank you very much for your advice. Could I use this map as a DEM https://environment.data.gov.uk/image/rest/services/SURVEY/LIDAR_Composite_1m_DSM_2020_Elevation/ImageServer ?

Kind regards,

Mikhail

Re: How to measure ruggedness by polygon

Omar_A — Sat, 04 Mar 2023 17:09:25 GMT

Hi Mihhail,

In terms of using a DSM instead of a DEM, it depends on your specific analysis and the data you have available. For example, DSMs include the height of all features on the ground surface, such as buildings and trees, while DEMs represent the bare earth surface. If you are interested in measuring the ruggedness of the bare earth surface, then you should use a DEM. However, a DSM may be more appropriate if you want to include all features on the ground surface in your analysis. Remember that DSMs may produce values higher than DEMs since they include the height of objects on the ground.

In any case, it is essential to understand the data's characteristics and limitations, such as its spatial resolution, accuracy, and vertical datum, before using it for any analysis or modelling.

Thanks,

Omar

Re: How to measure ruggedness by polygon

Mikhail — Sun, 05 Mar 2023 10:29:42 GMT

Hi Omar,

Thank you for your explanation. I found a DEM and followed the workflow you suggested. It all works, except for the last bit: I cannot find a Ruggedness Index tool. I have a Spatial Analyst license, but this tool is nowhere to be seen! Could you advise how you access it?

Kind regards,

Mikhail

Re: How to measure ruggedness by polygon

Omar_A — Sun, 05 Mar 2023 17:48:59 GMT

Hi Mikhail,

I apologize for the inconvenience. Please note that the Topographic Ruggedness Index (TRI) tool is a custom tool exclusively available for our Enterprise users.

However, I have investigated its structure and found that you can calculate TRI using a simple formula in Raster Calculator. I have provided a short video on creating TRI from DEM in ArcMap, which you can access through this link: (194) Topographic Roughness Index (TRI) from DEM / ArcGIS - YouTube

I hope this information is helpful.

Best regards,
Omar

Re: How to measure ruggedness by polygon

swfbtucs — Sun, 05 Mar 2023 23:51:32 GMT

You have to install the tool. See this:

https://www.esri.com/en-us/industries/water-resources/arc-hydro/downloads#arc-hydro-for-arcgis-pro

Re: How to measure ruggedness by polygon

Mikhail — Mon, 06 Mar 2023 11:57:09 GMT

Great, thanks! I am almost there, the only remaining problem is that I get an ERROR 000875: Output raster: workspace is an invalid output workspace. This seems to be a common problem, and I hope I'll find a way to resolve it.

Re: How to measure ruggedness by polygon

Mikhail — Wed, 08 Mar 2023 08:32:03 GMT

I am still struggling with this error. I went to Environment and changed the location of Scratch Workspace (see attached) but this did not help. What else could I try? It is so frustrating to stop just one step before solving a problem!

Re: How to measure ruggedness by polygon

swfbtucs — Wed, 08 Mar 2023 12:45:40 GMT

Mikhail,
I am sorry to have abandoned you. I have taken on another task right now that is demanding all of my time. And now my login is not working.

Frank Reichenbacher
Associate Researcher
[cid:image001.png@01D95181.1D105160]

Re: How to measure ruggedness by polygon

swfbtucs — Wed, 08 Mar 2023 12:47:27 GMT

Sorry to have abandoned you, but I have not actually installed the ArcHydro tools myself. I found the resource and then my time went away. I will get back to it, but don't know when.

Re: How to measure ruggedness by polygon

Mikhail — Wed, 08 Mar 2023 15:35:23 GMT

Hi Frank,

No problem, you have already helped me a lot! I am sure I will find a way to solve this issue.

Kind regards,

Mikhail