Processing billions of pixels over large areas at high resolution requires serious computing power and algorithms. The image above shows an Orthomosaic map with a Ground Sample Distance (GSD) of 3 cm spanning an area of over 250 acres. The original imagery was obtained using a Precision Hawk fixed wing UAV system and processed by DroneMapper cloud.
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DroneMapper recently acquired Trimble GPS RTK Base and Rover systems for ground survey to augment its aerial imagery collection operations. By combining ground truth, aerial targets and photogrammetric processing one may produce near survey grade digital elevation models (DEMs) and orthomosaics, precisely geo-referenced. Picture 1 illustrates the RTK setup. To get acquainted with the system operation we performed a number of surveys around the DroneMapper business property.
A search of the National Geodetic Survey (NGS) (https://www.ngs.noaa.gov/NGSDataExplorer/) identified three (3) high precision control points located at Blake Field airport, just north of Delta, Colorado. Picture 2 illustrates the control points on the NW side of the airport runway which is about 1 mile long. We utilized the base station to acquire Wide Area Augmentation System (WAAS) coordinates over the 1V9A monument and found the reported WAAS position was within 1 meter of the precise location in XYZ. We then keyed the precise position of the monument into the base station and used the rover to measure the other two monument positions.
If your application requires high quality imagery collection combined with precise control for the highest geo-spatial accuracies please call the DroneMapper team.
DroneMapper offers an affordable solution designed to enable continuous stockpile monitoring at any sized operation,Pierre Stoermer, CEO, said. The company’s main offering is photogrammetric software. “Either we process imagery for the client or the client licenses our Windows-based application(s) for their own use,” he said. “We also offer end-to-end training on drone and camera selection, use of aftermarket applications for autonomous, high-quality imagery collections, imagery processing and extraction of value-added info using GIS software.” Unlike many of its competitors, DroneMapper has already broken into the coal space.
For the last five years, Arch Coal used DroneMapper to process drone-captured images and data from its West Elk site. Arch also tapped the company to demo drone-based solutions at Thunder Basin, in northeast Wyoming. “They are interested in volumetrics, but they are really interested in safety and measurements of toes and crests, and to get measurements of slopes to determine if a slope is dangerous for cave-in,” Stoermer said. The demo went well, he said. “Arch Coal has provided positive feedback.”
DroneMapper is finalizing a white paper that will reveal how drone-based stockpile volumetrics solutions cut costs compared to traditional methods and facilitate continuous monitoring, Stoermer said. Toward both ends, multiple reports can be generated within a workday, empowering the miner with near-time actionable data, he said. To get there, the miner can purchase a perpetual license for the software ($2,000), run its own flights and handle its own data. “With a drone overflight, and if they did the processing themselves, they could eliminate the latency of sending images to us,” he said. “They could utilize our software process right after they collect the data and yield results within two to four hours or maybe less.”
The company offers training, which usually runs two days. It also offers exclusive online tutorials and hassle-free support, Stoermer said. “Our greatest differentiator is that you can speak with a human nearly anytime for support and there is no smoke and mirrors communicated.”
Thank you, The DroneMapper Team
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xyHt November Issue: http://bt.e-ditionsbyfry.com/publication/?i=445727
DroneMapper has been working with Arch Coal over the past 5 years in the development of an affordable work flow to accurately estimate coal stock pile volumetrics at the West Elk mine utilizing drone imagery collection, photogrammetric processing and GIS tools. The resulting work flow could lead to a significant cost saving by establishing accurate volumetrics with low latency compared with traditional manned aircraft operations. Further, more frequent drone acquired volume estimates can be used to check calibration of the real-time conveyor weight scale measurements to assure consistent calibration of mechanical systems.
Arch Coal – is the second largest domestic producer of metallurgical and thermal coal, with 96 million tons of coal sold in 2016. Arch is a well-positioned American coal company with large, modern, low-cost mining complexes and high-quality reserves in strategic U.S. coal supply basins. In total, Arch represents over 13% of America’s coal supply from their complexes in Colorado, Illinois, Kentucky, West Virginia, Wyoming and Virginia.
DroneMapper – provides photogrammetric cloud processing, desk-top software and GIS services for clients around the world. The team offers end-to-end drone operation services for imagery collections and processing as well as training. Typical products produced include high accuracy geo-referenced DEMs, DTMs, orthomosaics, point clouds, precision agricultural NDVIs, terrain contours and volumetric estimates, among others.
Arch Coal is interested in accurately quantifying their coal stockpile inventory on a regular basis. One example of this is the West Elk mine in Somerset, Colorado. The facility is a long wall mine where the mined coal is conveyed out of the mountain and deposited on the terrain surface. Figure 1 illustrates one of the stockpiles with three coal stack tubes (central left of image) with conveyor system. Ground control targets are used for every imagery collection to precisely align the imaged stockpile surface with the bare ground reference surface. Figure 2 shows the geo-referenced bare ground surface depicting zero volume or empty basin. This surface was precisely constructed using the control points that surround it. The colors represent the surface elevations with red the highest elevation and blue the lowest. Note the two ridges at the bottom of the surface illustration correspond to the ridge features seen in the stockpile image.
Figure 1: West Elk Stockpile
Figure 2: Geo-referenced Base Ground Surface
Imagery was collected by Arch Coal using a DJI Phantom 3 Advanced quad copter flying at approximately 300-400 feet above the ground/stockpile surface. At this elevation, the Phantom 3 will produce approximately a 2-inch pixel on the ground. A traditional 80% overlap (forward and side) grid was used for nadir imagery collection. The nadir imagery was augmented with an orbital oblique imagery collection to obtain stockpile surface data obscured by the conveyor system above the piles. Figure 3 illustrates the camera pose during the collection for both the nadir and oblique shots. DroneMapper has shown that the use of nadir and obliques provide for a higher quality digital elevation model (DEM) with less noise and artifacts than nadir alone. Once collection was completed the images were sent to DroneMapper for control pre-processing, full photogrammetric processing to generate the DEM and GIS manipulation for volumetric estimation.
Figure 3: Nadir and Oblique Collection Utilization
DroneMapper utilizes its Windows based REMOTE EXPERT software for 2-D control file generation and photogrammetry. The 2-D control file is generated using a tool that selects the number of images at a certain radial distance from the control by comparing the image geo-tags with the GPS coordinates of the control points. In this manner, an operator does not have to review every image for every control point in the scene, saving time. Each image identified with a control point is then zoomed in to select the pixel that the center of the control target appears. Figure 4 shows typical aerial target control points, 3-leg targets, used in image processing.
Figure 4: Mine Ground Control Points and Aerial Targets
REMOTE EXPERT uses this 2-D file and a 3-D file (defining control X,Y,Z coordinates) along with the imagery for DEM processing. Figure 5 shows the resultant DEM. Quality verification is performed by comparing the control elevations with the elevations of those points on the DEM to establish the root mean square error (RMSE) for the control. The elevation RMSE is then used to estimate the elevation accuracy which directly contributes to volumetric estimate uncertainty. Typically, we see elevation errors of less than 1 pixel or < 2 inches for this case. 
Figure 5: West Elk DEM
DroneMapper employs Global Mapper, from Blue Marble Geographics, for all GIS processing. The two surfaces, DEM and bare ground are terrain combined or subtracted from each other to yield a volume model of the stockpile. The image looks identical to the DEM above, however the base of the model is at 0 meters elevation. Global Mapper then quickly computes the volume of the entire pile or sub-piles within the overall stockpile by digitizing the selected pile of interest for computation.
Data Utilization:
Arch’s West Elk facility can now quickly and affordably utilize drone and imagery processing technologies to establish a comparative volumetric estimate at the times of their choice, weather permitting. This data may be used for calibrating or augmenting other weight or volume measurement equipment being used at the facility. The data also provides visibility on ground operations within the stockpile to assess inventories of coal in various processing stages for overall accurate inventory situational awareness.
Thank you, The DroneMapper Team
DroneMapper flew 4th Ave reservoir on November 14, 2017 using their Phantom 3 drone to collect imagery for precision digital elevation model (DEM) and orthomosaic generation of the site. Approximately 80 images were collected and processed via photogrammetry to yield the DEM and orthomosaic. Figure 1 illustrates the orthomosaic of 4th Ave reservoir, a few holding ponds and a small portion of Surface Creek to the northwest.
Figure 2 illustrates the DEM (zoomed in) constructed for the reservoir.
DroneMapper’s REMOTE EXPERT Windows application was used to generate the DEM and ortho from the image collection. Screenshots of the DEM and orthomosaic follow. REMOTE EXPERT generated the data products within one hour on our laptop, allowing processing in the field and mission verification prior to pack-up.
Figure 3 illustrates the contours generated for the DEM. The blue highlighted contour represents the reservoir’s maximum capacity. Global Mapper was then used to construct 1’ interval elevation contours as shown below:
The maximum capacity was calculated to be between 3 and 3.17 acre-feet. This is equivalent to approximately 1,000,000 gallons of water.
Phantom 3 Advanced Firmware: 1.8.10
MapPilot Version: 1.5.0 build 031916
DJI Go App Version: 2.8.6
Ipad Mini4 iOS Version: 9.3.3
Remote Expert Version: v0.8 b20170829-842 x64
Global Mapper Version: v19
Thank you, The DroneMapper Team
