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Accuracy of Stockpile Volumes from Drone images | Hammer Missions

Updated: Feb 2


stockpile volumes

Overview of Stockpile Volume Measurements with Drones


Measuring stockpile volumes is not a new concept, especially in the construction industry where they may measure stockpiles, and quantities of materials or use it for cut and fill purposes.


It has always been a challenge to know how much is contained in a specific stockpile or rubble pile but this is where volumetric measurement using drones can help alleviate that problem.


Here at Hammer Missions, we have developed a volumetric measurement method that works alongside our 3D Mapping software platform.


In this case study, we will be looking at a field test example using boxes to simulate a stockpile, measuring those boxes using our 3D Mapping Mission, and comparing the measurements taken at different heights from two different missions.


In the video below we look at how you create volumetric measurements using Hammer Missions




Case Study


As discussed earlier in this post we have used boxes to simulate a stockpile. Below we have detailed the measurement of each box, the quantity of each box, and the overall simulated stockpile area.


Single Box Measurements: 51cm x 29cm x 29cm


Quantity (number of boxes): 10


Total Stockpile Volume: 0.428 m3


stockpile of boxes


Drone Mission #1


Mission #1 was set at an altitude of 70ft and a ground offset at 20ft which resulted in a GSD (ground sampling distance) of 0.35cm


This means that every pixel in the drone image represents 0.35cm on the real ground. Learn more about GSD here. 💡

This mission was flown using the DJI Mavic 2 Pro.


The mission plan from Hammer Hub is shown below:


Hammer Missions Stockpile Volumes

Results


Stockpile Volume Measurement | Hammer Missions
Stockpile Volume Measurement

Actual Stockpile Volume: 0.428 m3


Measured Stockpile Volume: 0.33 m3


Measurement Discrepancy = 0.098 = ~0.1 m3


Mission #2


Mission two was set at an altitude of 45ft and a ground offset at 20ft which calculated a GSD (ground sampling distance) of 0.18cm


This means that every pixel in the drone image represents 0.18cm on the real ground. Learn more about GSD here. 💡

This mission was flown using the DJI Mavic 2 Pro.


The mission plan from Hammer Hub is shown below:


stockpile volumes on Hammer Missions

Results


Stockpile Volume Measurement | Hammer Missions
Stockpile Volume Measurement | Hammer Missions

Actual Stockpile Volume: 0.428 M3


Measured Stockpile Volume: 0.44 M3

Measurement Discrepancy = 0.012 = ~0.01 m3

Conclusion


As you can see from our field test results there is a substantial difference between the two missions captured at two different heights. Results from mission #1 (discrepancy = 0.01m3) are an order of magnitude less accurate than mission #2 (discrepancy = 0.1 m3)


The reason for this is...


At higher altitude, in our case 70ft, the GSD calculation is too high (0.35cm) to collect the quality of data that is required to make accurate measurements.

You will see in this example from mission one that the software has not been able to fully render the top of the simulated stockpile, highlighted below in red.


Stockpile

This inaccuracy will help determine the estimated volume, which in this case is out by quite a substantial amount.


Lowering the altitude and therefore lowing the GSD gives you a greater chance of collecting high-quality data and making your measurements more accurate.


The alternative option to lowering your altitude is to use a camera with a larger sensor and greater megapixels, this, in turn, will increase the quality of data that you are collecting from a higher altitude whilst being a safe distance from your asset.


The important thing to understand here, is that it's the GSD that matters, not the absolutely altitude. GSD is a function of the flight altitude and the camera used to capture data.

For more information on camera specifications please see our post:



All data was captured, processed, and measured using Hammer Missions.


If you would like access to the dataset please contact us on team@hammermissions.com



Summary


We hope this case study helps you understand how different heights can affect volumetric measurements when working in the field.


If you'd like to learn more about how to capture high-quality data and get the most out of your drone flights using our cloud-based platform, please feel free to visit our learning resources.


If you haven't got a Hammer account and would like to try Hammer Missions you can get started on our free trial.


To learn more about our enterprise solutions, including mission collaboration, data processing, and AI solutions, please contact us at team@hammermissions.com.


We look forward to hearing from you.


— Team at Hammer Missions

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