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Ridge and Valley Map from DEM

by Technical Evangelist on ‎08-20-2018 08:59 AM - edited on ‎09-13-2018 08:06 AM by Community Manager (687 Views)

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Description:

A Ridge Valley Map is created from the input DEM. The Map itself is a 2-bit coded file with ridges that have a pixel value of 1 and are colored red. Valleys have a pixel value of 2 and are colored blue. Voids (NoData) have value-based NoData (the value being set to 3). The background is 0 and is colored tan.

 

Ridge / Valley posts are determined by calculating the height in relation to the surrounding posts using a 7 by 7 pixel kernel, ignoring the immediately adjacent posts. If the center post is in the top specified percent it is considered a ridge post. If the center post is in the bottom specified percent then it is considered a valley post.

 

Left View shows a DEM, styled using the Relief Image Chain, right View shows the corresponding ridges (red) and valleys (blue)
Ridge_Valley_Results.PNG
 
 rv__v16_5_0.gmdx
Ridge_Valley_Model.PNG

  

Assumptions


The technique was originally implemented for coarser resolution Digital Elevation Models (e.g. 30m pixel sizes). High resolution DEMs may require different kernel sizes and percentage settings.

 

Input parameters: 

 

Input DEM: Select a DEM file to use to create the ridge valley map 

Input DEM NoData Value: If the Input DEM does not already have a NoData value (or mask) defined, the value to be considered as NoData should be entered here. DEfault is -32767.

Ridge Percent: Reports the surrounding height upper percentile ranking for post to be considered a ridge post. If the center post is in the top specified percent it is considered a ridge post.

Valley Percent: Surrounding height lower percentile ranking for post to be considered a valley post. If the center post is in the bottom specified percent then it is considered a valley post.

Ridge Valley Mask: Enter a filename for the output ridge valley map

 

Ridge_Valley_Run.png

   

 

 

Comments
by vasu
on ‎05-06-2019 02:26 AM

please share the gmdx file for RV

by sbent
on ‎05-06-2019 05:09 AM

The Ridge and Valley spatial model is accessible from the “Download model” link at the top of the article. Or you can click on the link below to download it.

 

Ridge and Valley Map from DEM

 

Kind regards,

 

Stephen Bent

Hexagon Geospatial Support

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