Workflow for filling in raster voids

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03-05-2019 03:23 PM
NathanDuncan
New Contributor III

Hi,

I have a DEM raster which contains stockpiles I'd like to get a volume measurement on. These stockpiles sit on a flat pad, which I unfortunately do not have a DEM raster of. My current workflow plan is to create a copy of the raster, clip out the stockpiles, fill in the gaps to create an assumed 'flat' plane underneath the stockpiles using 'Elevation Void Fill', and then subtract the difference between the original DEM and the modified DEM.

I'm currently experiencing two issues:

   1. I'm not sure I'm following the ideal workflow

   2. My current workflow is producing odd and unusable results

I'll go over my current workflow issues, but if anyone can suggest a more suitable workflow, that would be even better.

1. I create the boundary of the stockpiles to use in the clip tool

2. Data is clipped

3. Using 'Elevation Void Fill' the gaps are filled in. The data looks fine, but when queried the majority of the data is showing as NoData.

4. In an attempt to force the NoData to actual pixel values, I export the raster as a TIF. The NoData issues disappears, but is replaced with the below data. Obviously this isn't ideal and I'm wondering what happens to produce this when the above result 'looks' to be fine?

So, what is going wrong here? Am I way off in the workflow I should be following? Any help is appreciated.

Regards

Nathan

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PeterBecker
Esri Regular Contributor

If the Pads are flat then you do not need to create a DTM for the pad. The Volume of the pile = (Average Height - PadHeight) * Area. For a polygon get the average height of the DTM values and the size of the polygon. There could be a slight error in that that the polygon area is not exactly that of the pixels (aliasing). Best to get for the polygon the average height and number of pixels. Then compute areas as number of pixels * pixelsize^2.

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PeterBecker
Esri Regular Contributor

If the Pads are flat then you do not need to create a DTM for the pad. The Volume of the pile = (Average Height - PadHeight) * Area. For a polygon get the average height of the DTM values and the size of the polygon. There could be a slight error in that that the polygon area is not exactly that of the pixels (aliasing). Best to get for the polygon the average height and number of pixels. Then compute areas as number of pixels * pixelsize^2.

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NathanDuncan
New Contributor III

Hi Peter, thanks for the reply. That's exactly what I ended up doing and it worked fairly well.

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CodyBenkelman
Esri Regular Contributor

Nathan

search the GP tools for "volume" 

there are two tools that would have done this calculation for you immediately

Cody