Update DEM or elevation data

[BrianLomas]

Is there a way to update/change a DEM file or some kind of elevation layer which I could use as a terrain? Basically, I have a DEM which has current elevation and I have a 3d multipatch polygon which represents a road that will be built. The road construction will change the landscape which is represented in the multipatch polygon. I need the elevation of the multipatch to be represented in the terrain as well as the surrounding areas current elevation. I hope that makes sense.

I included a picture and you can see where the road is intersected by the terrain. Thanks for the help.

[JayantaPoddar]

Hi Brian,

You could follow these steps.

1) Convert the multipatch to Raster. Keep the XY Resolution (cell size) same as that of the DEM.

Multipatch to Raster—Help | ArcGIS for Desktop

2)Now if I want to add up the value of "New_DEM" with the old "DEM" raster, I would  use Raster calculator (Spatial Analyst) with a similar expression:

("New_DEM" + "DEM")

[BrianLomas]

I converted the multipatch to a raster. Is there a way to combine or merge the two rasters together, overriding the existing raster's info only where the new raster overlaps?

[JayantaPoddar]

Did you try step 2 that I suggested?

[BrianLomas]

Yea, when I did that it seemed to only change the converted multipatch raster.

[JayantaPoddar]

Ok. Try this

Con(IsNull("New_DEM"),"DEM", ("DEM" + "New_DEM"))

[DanPatterson_Retired]

You have to ensure that the analysis extent is the same... You can use the Con—Help | ArcGIS for Desktop

[BrianLomas]

I ran Con(IsNull("New_DEM"),"DEM", ("DEM" + "New_DEM")) first then I tried changing the extent and running it again, both gave me the same result (pic attached). I'm probably making this harder than it really is. Thanks for your time and patience.

[DanPatterson_Retired]

I am assuming it looks fine if looked at in 2D?  Just the patch area itself?  in otherwords without the DEM.  They are in the same Z units? If a scaling factor was applied, they are both the same?  That is why I initially thought it looked like the feature was being 'clipped' when it was draped over the surface.  In such cases, I applied a small offset and/or extrusion for visual purposes.  So in short.. make sure it is indeed continuous in 2D and that all the data got converted to data etc

[BrianLomas · Accepted solution]

I started from scratch by matching scales between the two files, then matched projections, then used the "mosaic to new raster" tool; this seemed to work. Thanks a lot for pointing me to in the right direction guys, you were a big help.