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Cut Fill (3d analyst tool) - understanding the values in the attribute table

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09-13-2023 05:16 AM
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PoulSkræ
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Hi - I hope someone can explain something to me as if I was 5 years old 😂  I read all the documentation, but it is still not completely clear to me.

Anyhoo.  I have two diffent 3d surface models of an area. These were made with drone flight with 6 months apart and converted into a 3d dwg model. This was done by the external partner who also did the drone flight. I've been asked to perform a calculation on the complete amount of soil added to the site. 

I managed to do the calculations based on the following workflow.

- convert both 3d models into a raster images.
- calculate the cut fill based on these two raster images.

The Cut Fill operation gives med an overview with 3 colors.  Net Gain, Unchanged and Net Loss.  The attribute table show me a long list with 196 object IDs.  Each row has the following:  ObjectId, Value, Count, Area and Volume.

The documentation says that negative values are soil added and positive values are soil removed.  So far to good.  This is where I'm getting a but confused.  I just want to calculate the total change in volume for the entire area.

The Question:

When looking into the documentation on this link it show a diagram and an example of the attribute table.  In the volume field (the image) it shows to areas with a volume field of 400 in each field.  In the Attribute table it shows a row show there are a "count of 2" each with a "volume" of 400.  So does this mean, that in order to get the correct volume in my final calculation i need to take all the "volume" and multiply it with the "count" to get the correct volume in my cut fill analyse?  In this case the correct value would be 800, since there are two fields each with a value of 400?

Cut Fill (3D Analyst)—ArcGIS Pro | Documentation
PoulSkr_1-1694606708577.png

Here is a screenshot of my own calculation.  In this calculation there is a row where the count is 8986 and the volume is -725,000929.  So is the volume here already calculated correctly or should I multiply the volume with the count in order to get the correct number?  (8986 * -725,000929 = -6514858,347994)

So should I do this calculation for each row and add/subtract them all, before I get the correct amount of soil added to the site?  Or should I just calculate the volume for each row to get the correct result?

PoulSkr_2-1694606996512.png

 

Final question - is there a smarter way to get the final calculation 😄  I hope some here can help me - the more I look into the help file the more confused I get.

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