Volumetrics in ArcMap

Introduction

Applications of volumetrics can be seen throughout the world.  An example of using volumetrics can be seen in measuring volumes in mounds and in buildings. With UAS platforms, using volumetrics can cut down time and improve accuracy.  In order to gather this data one must have the bulk density from the mound. 

Methods

In our lab, we were assigned with using ArcMap to figure out the volumes of different mounds from their DSMs.  The first example is from the Wolfcreek data set.  First we must choose a mound to work with, then we have to clip it to differentiate from the whole DSM.  Below is an image of the first step of making a clip of the mound.

To do this one must use the editor tool to trace out the desired area.  It is recommended to get as close as possible to the mound for taking measurements.  Having the line closer in is preferred because it will make the data more accurate rather if the line is farther away and including more ground.  

The next step we took was to extract by mask with the mound clip.  To do this we used the extract by mask tool and used the original DSM as the input raster.  Below is the clip with the DSM limited to that specific clip that helps us get the volumetrics.  

Once we have the clips extracted, we can perform a surface volume analysis.  This will allow to read the measurements for the separate mounds.  Below is how the data is found for each mound.

The tables show the lowest elevation of the mound called plane height and the volume of the mound.  The first mound had a volume of 506.45m^3, second was 2,339.44m^3, and the third was 223,472.97m^3.  

Discussion

Another interesting feature in ArcMap is the feature to Cutfill across two DSMs.  This analyzes the changes between the images and elevation.  Below are the before and after images from the Litchfield Mine data.  The before image was made on July 22 and the after was on September 30.

Above is on July 22

Below is on Sept 30

In order to perform the Cutfill function, we first had to resample the DSM.  This is because Cutfill with millimeter accuracy would take too long and is not necessarily require that much detail.  To streamline the process we resampled the data to ten centimeters.  Below is the Cutfill function result.  The red represents the net gain and the blue represents the net loss.  There is also a color for unchanged but for this the elevation must change by absolutely nothing in order to show.

Conclusion

Using UAS for volumetrics has proved to make the whole process much more efficient.  The data has been incredibly accurate and has put some ground crews to shame.  It is important to note that to use the Cutfill function, you must have very precise data in order to have a successful Cutfill.  Having GCPs will greatly improve your results.  They should be placed around the same locations for different times to have better results.  Knowing this allows us to realize that this process is not always fully accurate but can help mitigate any outside altercations.