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Geo-referenced orthophotos of the Tanana River, Alaska, acquired July 24, 2019

Published by U.S. Geological Survey | Department of the Interior | Metadata Last Checked: July 16, 2025 | Last Modified: 20210503
This data release consists of an orthophoto of the Tanana River in Alaska acquired on July 24, 2019. The orthophoto was 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 Tanana 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 image had a spatial resolution (pixel size) of 0.1 m. The image is saved as a GeoTIFF file 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 this orthophoto was to serve as a base for geo-referencing the video described in a related data release accessible from the parent landing page cited above.

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