The BLM National Operations Center (NOC), as part of an ongoing pilot project with the Royal Gorge Field Office (RGFO) in Canon City, Colorado, is using remotely sensed imagery from unmanned aircraft systems (UAS) for mine site production verification (PV). The current PV process is labor-intensive, includes extensive field work, and is cost prohibitive, which results in a less than optimal number of mine operations being evaluated. In September 2016, the RGFO purchased high-resolution UAS imagery of the Indian Sunset mine site near Westcliffe, Colorado, from Leptron Unmanned Aircraft Services, LLC. In November 2017, the NOC UAS crew re-collected high-resolution stereo imagery utilizing the 3DR Solo of the Indian Sunset mine site. High-resolution digital surface models (DSM) (1.14 to 1.5 cm/pixel) of both datasets were produced and then analyzed to determine the volume of material extracted from the northern part of the mine site between the two acquisition dates. Accurate differencing was accomplished using a rigorous photogrammetric (structure-from-motion) workflow, with each dataset aligned in the same 3D space and georeferenced using one set of surveyed ground control targets collected in September 2017. The ease of collecting UAS acquired imagery and the ability to align temporally separate datasets into the same 3D space to measure the differences of volume offers a more efficient form of PV with comparable results to ground-based surveys, saving time and money.
High-resolution digital surface models of the Indian Sunset mine site (area of interest outlined in red) used to estimate the volume of material extracted over a 14-month period.