topic Re: Adding a barrier with height on a Raster DEM in ArcGIS Mapping and Charting Questions

Adding a barrier with height on a Raster DEM

AlexRepole — Mon, 12 Jun 2017 11:42:02 GMT

Hi all,

I am currently working on a project in which I am modelling lava flows (using a plugin). I have run all eruption simulations but now want to add barriers/walls that would change the height of the DEM so I can assess mitigation strategies.

I have tried drawing polygons and lines and building mosaics but they haven't worked.

Is there a way of changing the height of certain pixels or drawing a polygon/line to make it part of the raster DEM?

Any advice/help is much appreciated!

- A

Re: Adding a barrier with height on a Raster DEM

JayantaPoddar — Mon, 12 Jun 2017 12:14:55 GMT

Check if this works.

1. Draw a line feature class representing the barrier (with Height_of_Barrier Field). I think you have done this step. Ensure the coordinate system of the line is same as that of the DEM Raster.

2. Convert Polyline to Raster. Use Snap Raster Option in Environment settings to the tool. Also define the same Cell_Size as the DEM Raster.

3. Using the Barrier Raster, convert all its NoData values to 0. (No need to do this step)

4. Use Raster Calculator to sum/add The Barrier Raster with the DEM Raster with the following expression.

Con(IsNull("Barrier_Ras"),"DEM_Ras",("Barrier_Ras"+"DEM_Ras"))

Re: Adding a barrier with height on a Raster DEM

AlexRepole — Mon, 12 Jun 2017 13:11:28 GMT

Thanks! Everything works apart from the last step. The resulting map shows only a tiny area around the barrier rather than the whole DEM

Re: Adding a barrier with height on a Raster DEM

JayantaPoddar — Mon, 12 Jun 2017 14:03:52 GMT

Try the following expression in Raster Calculator

Con("Barrier_Ras" > 0, ("Barrier_Ras" + "DEM_RAS"), "DEM_RAS")

Re: Adding a barrier with height on a Raster DEM

AlexRepole — Tue, 13 Jun 2017 10:35:27 GMT

The same is happening again. The DEM keeps disappearing and all that remains is a tiny area around the barriers

Re: Adding a barrier with height on a Raster DEM

AlexRepole — Tue, 13 Jun 2017 10:59:55 GMT

Would it work if I just converted my DEM to points and edited the points, then converted it back to raster?

Re: Adding a barrier with height on a Raster DEM

JayantaPoddar — Wed, 14 Jun 2017 07:31:54 GMT

Sorry for the delay. You could use the following expression in Raster Calculator.

Con(IsNull("Barrier_Ras"),"DEM_Ras",("Barrier_Ras"+"DEM_Ras"))

Also updated my original reply with all the steps.

Re: Adding a barrier with height on a Raster DEM

AlexRepole — Wed, 14 Jun 2017 09:11:16 GMT

The result is still only the small area around the barriers

Re: Adding a barrier with height on a Raster DEM

JayantaPoddar — Wed, 14 Jun 2017 09:17:11 GMT

Did you check my first reply. I eliminated step 3. It worked for me. I also added the DEM Raster to the Processing Extent (Environment setting of the tool- Raster Calculator)