Aerial (drone) surveying leverages drones to capture geo-tagged imagery of the stockpile and its immediate surroundings.
Once the geotagged photos have been gathered from multiple angles, with high degrees of overlap (70-80 percent sidelap and frontlap), they are uploaded into software that then uses photogrammetry to generate a high-resolution orthomosaic map, point cloud and 3D model.
Where typical GPS surveys for stockpile volumes are measured in square meters per point, aerial surveying creates hundreds of points per square meter.
In a nutshell, aerial imaging is a trade-off between the low cost, speed, and site safety offered by a drone survey versus the accuracy of a GPS survey. Martin Remote sensing Corporation conducted a comparative study between the accuracy of a drone survey versus a GPS survey yielded a variation of only 0.6% between the two methods of survey for an aggregate pile of approximately 4,400 cubic yards. (see: Assessing the Accuracy of Stockpile Volumes Assessed Through Aerial Surveying , http://resources.dronedeploy.com/hubfs/Case%20Studies/Martin-Remote-Sensing-Case-Study.pdf?hsCtaTracking=c3c92dbf-7789-4935-8bcc-a9f4b8094b59%7C6ffdc8e2-dfff-47c7-9acf-d482b807bd10 , 21 Sep 2017).
The 2D and 3D orthomosaic and elevation model on this page are of the log sort yard in Thorne Bay. Approximately 90 images were captured in less than 15 minutes using one of SEAKdrones’ Phantom 4 drones. The orthomosaics were prepared using a mapping algorithm to “stitch” together approximately 90 getoagged images, with resolution of 2in/pixel.
Results:
Stockpile dimensions (approximate): 37 ft. high, 100 ft. wide (center), 0.4 acre footprint Stockpile volume (approximate): 8,475 cubic yards
Definitions:
Geotagged images are images to which a geographical location is assigned.
Orthomosaic maps are composed of photos corrected for lens distortion, camera angle, and topography to yield maps with high relative accuracy.
Note: there is a loss of resolution in the process of screen captures and/or conversion into jpegs for blog software.