Lab #7 Volumetrics

Introduction

Using volumetrics is a key tool in many industries, including the UAS industry. Volumetrics allows you to measure the volume of an area, object, or landmass using specific data and points. Volumetrics allows you to measure volume changes over time, which is what we did in this lab. We used Pix4D and ArcGIS Pro to calculate 3 large piles over a period of 3 months. We use UAS to collect this data because it is a more efficient way to get aerial data. 

Methods

This is a photo of the three piles before I used the volume tool to outline them. We used the volume of these three piles over the course of three months to find the changes in volume that occurred.

Figure 1: Wolf Creek Aggregate Piles

I then used Pix4D's Volume tool to draw accurate and specific lines around each pile. When the volumetrics are calculated, it will display their volumes and their elevation related to the base of the worksite. The tools show lower areas in green and higher areas in red. I used a triangulated base as a reference for this calculation as they change over time. There are many ways to calculate volumetrics in Pix4D. I chose the quickest and most efficient way which can be compared with a more slow and precise approach. Both methods will give you similar results if done correctly.

Figure 2: Calculating Pile Volumetrics

After I drew lines around each pile I calculated the volume of each pile separately using the volume tool. 

Figure 3: Volume Tool

Figure 4: Volume Tool Compute

Pile A is the smallest pile, Pile B is the second largest pile, and Pile C is the largest pile. I computed all these volumes separately. After that, I calculated these volumes with different bases.

Figure 5: Pile A Volume

Figure 6: Pile B Volume

Figure 7: Pile C Volume

Figure 8: Volumetrics with Different Bases 

The triangulated base seemed to be the best fit for ArcPro's volumetrics. Next, I clipped the data using the Litchfield DSM and the clip tool. And resampled each pile data.

Figure 9: Resample Tool 

Figure 10: DSM Clip of all Piles

To create a clip I needed to create a new feature class. Once the clip was created I used the "extract by mask" tool to pull the data out of the DSM. I created each new clip pile as 10 centimeters so they correlate with one another perfectly. 

Discussion

Using and developing the new skills I acquired while using ArcPro's volumetric tools was a great learning experience, I used these skills on the Litchfield operation. This operation was examined once every month for three months. Each month the size of the pile changed in size and volume, you can see this change in figures

The Ground Spaced Distance table showed the change in the height of the DSM through July, August, and September. It shows the minimum and maximum heights, the UTM zone, and the Ground Spaced Distance among the data. 

Resampling is a very important step in calculating the volumetrics. Resampling helps correct the difference between data that is identical. Precise ground control is crucial for having accurate data while comparing them to other data sets. 

"There are four options for the Resampling Technique parameter:

Nearest—Performs the nearest neighbor assignment and is the fastest of the interpolation methods. It is used primarily for discrete data, such as a land-use classification since it will not change the values of the cells. The maximum spatial error will be one-half of the cell size.

Majority—Performs a majority algorithm and determines the new value of the cell based on the most popular values within the filter window. It is mainly used with discrete data just as the nearest neighbor method; the Majority tends to give a smoother result than Nearest. 

Bilinear—Performs a bilinear interpolation and determines the new value of a cell-based on a weighted distance average of the four nearest input cell centers. It is useful for continuous data and will cause some smoothing of the data.

Cubic—Performs a cubic convolution and determines the new value of a cell-based on fitting a smooth curve through the 16 nearest input cell centers."

(This data was sourced from https://pro.arcgis.com/en/pro-app/tool-reference/data-management/resample.htm)

Figure 11: Pile Height Changes

I next used the "cut fill" tool to input one raster dataset before and another after. This cut fill allows you to see the difference in the landmass of the piles from 7/22/17 to 9/30/17. Areas in red reached higher heights and sizes, while areas in blue lost size. Maps like these allow you to examine data over time and see how the product changes.

Figure 12: Cut Fill of Litchfield Operation

This wolf creek DSM and Orthomosaic shows the hillshade tool to visualize all three piles. The hillshade has a specific color shade to show you the base to the top of each pile. The shade starts at green is the base or the lowest point of the pile, then it slowly turns yellow as the elevation rises until it hits the peak which is the reddish-orange areas. 

Figure 13: Volumetric Data of Wolf Creek Piles

Figure 14: Hillshade of Wolf Creek Piles

 The final three figures display the changes in the Litchfield pile over the course of three months. In the first figure the date is July 27th, in the second figure is August 27th, and the third figure is September 30th. Each UAS flight shows a change in the size and data of the pile. Resampling helped keep the data accurate and the hillshade helps you visualize the changes in size and elevation.

Figure 15: Litchfield Pile 07/2718

Figure 16: Litchfield Pile 08/27/18

Figure 17: Litchfield Pile 09/30/18

Conclusion

This lab taught me how important volumetrics are in my field and industry. It was a great first lesson on teaching me how to use volumetric tools to make simple data more visual and professional.

I learned that not only are volumetrics important in the UAS field, it is also important in other industries such as mining, construction, and agriculture. volumetrics can help construction managers see their progress throughout the process and learn how to be more efficient. agriculture can keep watch over their fields and crops. Workers can see the progress made on the mine and how deep they have gone over the process. Volumetrics is an easy and highly useful tool to learn overall.