Geo-referenced orthophotographs of the Snow River, Alaska, acquired September 1, 2018

This data release consists of orthophotographs of the Snow River in Alaska acquired on September 1, 2018. The orthophotographs were produced from images obtained using a Hasselblad A6D-100C 100 megapixel digital mapping camera deployed within a pod mounted on the landing gear of a Robinson R44 helicopter. Images were acquired as the helicopter transited a series of flight lines designed to provide complete coverage, with ample overlap, of the study area along the Snow River. Also within the pod was an ATLANS GPS/Inertial Motion Unit (IMU) that recorded the position and orientation of the platform during the flight. This information was used to geo-reference the images by performing aerial triangulation and bundle adjustment within the TerraSolid software suite, which was also used to produce a LiDAR DEM that was incorporated into the orthophoto production process. The resulting orthorectified imagery had a spatial resolution (pixel size) of 0.05 m. The imagery is saved as a GeoTIFF files with an embedded header that contains the spatial referencing information for the image; the projected coordinate system is UTM Zone 6N, NAD83. The main purpose of these orthophotographs was to provide an ancillary dataset that could be used with a related lidar product and data release.