5

Is it possible to invert a slope map same as invert a surface?

I found code on this website https://support.esri.com/en/technical-article/000006694

The code is following:

(([elevgrd] - Z_Max) * -1) + Z_Min

Can I use slope map instead of elevgrd ,maximum slope value instead Z_Max and minimum slope value instead Z_Min?

I want to do something like least cost path analysis in ArcGIS but my main goal is to find the hardest path between two points.

  • Did you try with raster calculator? – aldo_tapia May 25 '18 at 22:30
  • Yes, I used raster calculator. I wrote there (([slope_map] - 40) * -1) + 1. 40 was the highest value of slope and 1 was minimum value – rominka198 May 25 '18 at 22:31
  • To invert the scaling on any value (Vin), you can use the following: 1. Vrange = Vmax - Vmin, 2. Vout = (1 - (Vin - Vmin) / Vrange) * Vrange + Vmin – WhiteboxDev May 26 '18 at 13:45
0

Technically No you can't use Slope

Instead

You should use (Elevation Raster) instead of (Slope raster)

Why

Because (Elevation Raster) represents the surface but (Slope Raster) is representing the most frequently run on an elevation dataset.

So the (Slope) is just a characteristic of the elevation which it can be computed using

slope_degrees = ATAN ( √ ([dz/dx]2 + [dz/dy]2) ) * 57.29578

According to ESRI, Raster Surface tools in ArcGIS considers that Slope is one of the surface tools.

--How the inverting surface works:--

In general, it's mathematical approach to be done.

ArcGIS Code:

(([elevgrd] - Z_Max) * -1) + Z_Min

Where: [elevgrd] is the name of the input surface, Z_Max is the surface maximum and Z_Min is the surface minimum.

In your case (Wrong):

Because you used the slope values not the elevation values

[elevgrd]  = [slope_map]

Z_Max = The maximum slope from your raster = 40
Z_Min = The minumum slope from your raster = 1

Example As you can see from both pictures how the max and min values are different (Elevation VS Slope)

enter image description here

enter image description here

  • My main problem is that I want to do something like least cost path analysis in ArcGIS but my main goal is to find the hardest path between two points. I followed course here: youtube.com/watch?v=d0Eywj4pIu8 – rominka198 May 26 '18 at 14:40
  • My main problem is that I want to do something like least cost path analysis in ArcGIS but my main goal is to find the hardest path between two points. I followed course here: youtube.com/watch?v=d0Eywj4pIu8 I tried to do it with original surface grid and also with inverting surface grid (computed by equation:(([elevgrd] - Z_Max) * -1) + Z_Min) but results were in both cases same and not correct. Then I tried to invert slope map with the same equation (([slope_map] - the highest value of slope) * -1) + min value of slope ) and result was better – rominka198 May 26 '18 at 14:48
0

Per your comment, if you want to have steeper slopes to have lower cost for a least cost analysis, just subtract the slope in degrees from 90. So near vertical slopes will have a cost of near zero and flatter areas will have a cost nearer to 90. Eg

90 - [slope degrees]

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.