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

Published by U.S. Geological Survey | Department of the Interior | Metadata Last Checked: July 16, 2025 | Last Modified: 20210317
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.

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