- Switzerland
Stockpile measurement: drone vs. terrestrial laser scanner
For more than two decades, Trimble terrestrial laser scanners (TLS) have provided a gold standard in ground-based surface measurements for stockpiles, quarries and construction sites.
But it can take a day to run a scan of just a 40 acre (20 ha) site, whereas stockpile measurements with drones can cover the same area in minutes.
Recently, Swiss firm Lerch Weber AG tested Wingtra’s new SURVEY61 to see how it compares accuracy-wise when flown with the WingtraRAY survey drone. What they found is something that signals a clear evolution in aerial survey technology.
Challenges
Volume tracking results in huge resource losses if it’s not done accurately. Traditional field equipment involves a lot of field time to get the highest accuracy possible.
This reduces capture frequency due to the time and field resources required. Ground-based scanners can also miss some areas depending on how they’re positioned.
Solutions
Drone stockpile measurement massively cuts field time and crew hours for repeated volume surveys.
If efficient results prove to be within the accuracy range of ground-based methods, this opens the opportunity to run volumetric surveys more often.
The capture is more comprehensive as well, ensuring the most useful results possible.
TLS vs. drone measurements
For reference, Lerch Weber found that the volumetric difference between the terrestrial scan data and SURVEY61 data would fit into four carry-on-size suitcases.
For us, it’s not enough just to see something work faster. We need to know that the quality of the results is to our high standard.
In this comparison, we see something remarkable—drone photogrammetry and terrestrial scanning that produce nearly identical volumetrics results.
This is a clear signal for us to move forward in transitioning to Wingtra for our surveys.
The comparative accuracy of the SURVEY61 data really comes to life in this cross section scan graph of one of the stockpiles, an analysis that was performed repeatedly across stockpiles for this study. The white points represent Trimble data and the colored points represent Wingtra data. Zooming in on the cross section shows how closely the SURVEY61 point cloud matches the Trimble point cloud.
Study logistics
The Trimble terrestrial laser scanner already cuts a volumetric survey in this Lostorf gravel pit down from several days and two field crew to one day with one surveyor.
The next leap forward is drones, which cut time down to minutes. For repeat surveys, this offers massive return on investment in terms of time and labor costs.
Lostorf, Switzerland
Annual Lostorf gravel pit survey
What is volumetric analysis of a stockpile?
Stockpile volume surveys rely on measurements of the pile surface to derive the cubic volume of the contents.
Terrestrial laser scanners (TLS), or drone photogrammetry or LIDAR sensors can be used to capture millions of data points to offer a dense “blanket” of data points. Software uses these points to measure the surface area and derive the cubic volumes beneath.
Taking a cross section of these points across the mid-section of a stockpile enables a closer look at the measurements and even a comparison of capture methods.
Save time and money with better drone stockpile measurements
Extreme field time
On and off field in 1 hour
Field expense + exposure
Setting up extensive ground points on active earthworks sites can take hours, exposing workers to conditions and safety hazards.
Minimized field time
GCPs: correcting the data
CPs: validating accuracy
Missed survey areas
Terrestrial scanners must be positioned to capture all surfaces and can miss areas.
Comprehensive coverage
Whole day of work
Scanning with ground equipment can take a whole day on a 40 acre (20 ha site).
One hour of work
An efficient, high-accuracy drone can cover the same area in 13 minutes bringing total field time to an hour.
To get a complete data set of a typical gravel pit using terrestrial scanning, it would take a full day, or six to eight hours, due to the need to move around stockpiles and walls to avoid obscured areas.
With Wingtra it took about an hour with field setup included.
The evolution of aerial capture accuracy
Lerch Weber has a reputation for high-accuracy, high-quality results to maintain. So they test systems thoroughly and even publish results on these tests. When they first looked at fixed-wing options, they ran this same comparison with eBee. Their research, published in 2018, shows how far the technology is advancing with the Wingtra platform.
Who is Lerch Weber?
For over a hundred years, Lerch Weber have built a strong reputation as an independent and competent survey contractor.
Their dynamic team develops targeted solutions for every client’s needs. As enforcement surveyors for the districts of Olten and Gösgen, Lerch Weber provides survey data for property security as part of the land register, as an independent, conscientious, and neutral party.
Moving with the times, they adapt to the latest technologies and know how to use them correctly.