I need to pull the slope of the roads, when I do the slope of the DEM map I get a slope of 0-330 percent, how to do the slope of 0-100% of the roads?

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03-18-2020 10:36 PM
StefanSibinovic
New Contributor

Universiti belgrade

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6 Replies
DanPatterson_Retired
MVP Emeritus

See

https://pro.arcgis.com/en/pro-app/tool-reference/spatial-analyst/con-.htm 

Some variant of the examples there.

Basically if the slope is <=100% return the slope value otherwise some other value like -1 or even SetNull

Con(Raster("slope") <= 100, "slope", -1)
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DavidPike
MVP Frequent Contributor

Dan is correct in how to convert this, however this may also be a mis-understanding of the percentage slope. 

This is rise/run *100, meaning a 100% slope is 45 degrees, and a 330% slope is 73 degrees.

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StefanSibinovic
New Contributor

Yes 330% is 73 degrees, now I'm interested in what to do, get a road slope of 0-100% because my task requires a road slope of 0-2, 2-10, 10-30,> 30%

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DavidPike
MVP Frequent Contributor

The easiest way is to symbolise the data in the classes you need, then drag that layer into the Reclassify tool, which should add those break values for you to change.

here is the difference between geoid and ellipsoid

it can be recoded by the Reclassify tool

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StefanSibinovic
New Contributor

Ok, i go to reclassify, but Roads cannot be in slope 330, max value is 100%, and I need to turn those 330 into 100%.

The terrain can be 330 (73 degrees) roads max 100% (45 degrees)

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DanPatterson_Retired
MVP Emeritus

I thought the idea was to identify the areas where the slope was a maximum of 100%, and retain those slope values if they were less than that.  If so, use the Con symbol, if not, then symbolize the data.  You can reclass the values > 100% to be 100%, but that would be misleading.

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