The Texas Dept. of Transportation has benchmarked and adopted an iPhone app to measure its stockpiles. The app works by uploading a video of the stockpile to a cloud server, which turns the data into a 3D model to calculate its volume.
Stockpile Reports Inc., Redmond, Wash., developed an app of the same name for aggregate suppliers measuring stockpiles 3,000 cu yd and larger, says Mark Bradshaw, TxDOT procurement administration manager. "They documented accuracy of plus or minus 2% on these large stockpiles" but reported a lower accuracy for piles smaller than 100 cu yd, he says. For stockpiles smaller than 100 cu yd, Bradshaw's team did its own tests on the app against light detection and ranging (LIDAR), GPS and employee measurements and confirmed its accuracy to be plus or minus 1.5%. Bradshaw adds that the app is easy to use and accurate and improves safety.
"Collecting data in the app is like shooting a panoramic photo," says Maury Margol, head of business development at Stockpile Reports. A user places two orange construction cones parallel to the stockpile and exactly 25 ft apart on center. "The cones are like a legend on a map, giving the computer a point of reference," says Margol.
Keeping the top and bottom of the pile in the frame, the user walks the 25 ft from the first cone to the second cone, then keeps circling the pile until he passes the first cone again, ending at the second.
"Once you upload the video, the real magic happens," says Margol. Cloud computers using photogrammetry turn the video's digital pixels into XYZ coordinates, creating a 3D model of the pile. Margol wouldn't disclose pricing but says the service is subscription-based and "makes financial sense for companies doing 10 or more measurements a month."