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C 0 L 0 RAI 0 <br /> Division of Reclamation, <br /> Mining and Safety <br /> Department of Natural Resources <br /> Interoffice Memorandum <br /> September 10, 2019 <br /> From: Leigh Simmons <br /> To: Robin Reilley <br /> 7 <br /> Subject: Williams Fork Mine(Permit No. C-1981-044) <br /> Cheat Grass Aerial Survey <br /> As you requested, I accompanied you to the Williams Fork Mine on August 27, 2019, and completed an <br /> aerial survey using an Unmanned Aerial Vehicle (UAV, or"drone").The intention of this memo is to <br /> provide you with a summary of the procedures I followed to collect and then process the imagery, and <br /> also to present some analysis of the data products. <br /> Procedures for the use of UAVs have not yet been formalized by the Division, although some initial <br /> testing has been completed to provide a basis from which to proceed. For this project, imagery was <br /> collected using a DJI Mavic 2 Pro.The image collection missions were programmed using the Pix4D <br /> Capture app running on a Samsung Galaxy S9+. Images were written to a micro SD card. Following the <br /> inspection the images were downloaded from the card and shared using google drive (complete <br /> metadata is automatically appended to each image). <br /> A total of 3 flights were required to collect 2 sets of data. Both data sets cover the same general area. <br /> "Lower"was flown at 50m above the take-off location, "Higher was flown at 100m. <br /> All flight missions were flown as"polygon"types using the following collection settings: <br /> • Camera Angle=90' <br /> • Image Overlap=20% <br /> Images were processed on a 64-bit Lenovo desktop PC,with an Intel Core i7-7700 CPU and 32GB of installed RAM, <br /> using Global Mapper v20.1 (specifically the Pixels to Points tool,which is part of the LiDAR module). <br /> Settings on the processing tool were adjusted to optimize the quality of the 2D orthoimage. <br /> • The processing tool was configured to generate a 2D orthoimage from a 3D mesh. <br /> • A standard 3x3 resampling filter was applied to the orthoimage to remove noise. <br /> • Image sizes were reduced by a factor of 4 to enable faster processing and mitigate issues with memory <br /> requirements. <br /> • An incremental analysis method was employed,which treats each image in sequence and is recommended <br /> as the default option. <br /> c k. <br /> i :tee. L <br /> 1313 Sherman Street Room 215 Denver CO 80203 P 303.866.3567 F 303.832.8106 htt //mining.state.co.us * ' <br /> Jared S. Polis, Governor I Dan Gibbs, Executive Director I Virginia Brannon, Director .. <br />