High-resolution image sequence from the Salcha River, Alaska, August 31, 2018, for Particle Image Velocimetry
Dates
Acquisition
2018-08-31
Citation
Legleiter, C.J., and Kinzel, P.J., 2020, Field measurements of flow velocity and optical image sequences acquired from the Salcha and Tanana Rivers in Alaska in 2018 and 2019 and used for particle image velocimetry (PIV): U.S. Geological Survey data release, https://doi.org/10.5066/P9IJ20O4.
Summary
This data release consists of a sequence of high spatial resolution optical images used to derive remotely sensed estimates of surface flow velocity via particle image velocimetry (PIV). These data were acquired from the Salcha River in Alaska on August 31, 2018, along with field measurements of flow velocity used to assess the accuracy of image-derived velocity estimates. The images were 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. Image sequences were acquired at a frame rate of 1 per second (1 Hz) while the helicopter hovered in a fixed location approximately 200 m above the river. Also within the pod was an ATLANS GPS/Inertial [...]
Summary
This data release consists of a sequence of high spatial resolution optical images used to derive remotely sensed estimates of surface flow velocity via particle image velocimetry (PIV). These data were acquired from the Salcha River in Alaska on August 31, 2018, along with field measurements of flow velocity used to assess the accuracy of image-derived velocity estimates. The images were 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. Image sequences were acquired at a frame rate of 1 per second (1 Hz) while the helicopter hovered in a fixed location approximately 200 m above the 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 SimActive Correlator3D software package. The bundle adjustment phase of this process also incorporated surveyed ground control targets that were placed in the field and were visible in the images. The resulting orthorectified images had a spatial resolution (pixel size) of 0.018 m and effectively stabilized the image sequence prior to PIV analysis. The images were converted to grayscale and saved as TIF files with corresponding world files (*.tfw) that contain the spatial referencing information for each image; the projected coordinate system is UTM Zone 6N, NAD83. The sequence consists of 68 individual images representing over one minute of data collection. The entire sequnce of TIF images and worldfiles is contained within a zip archive.
For questions concerning this data set, please contact:
Dr. Carl J. Legleiter - cjl@usgs.gov, 303-271-3651
Geomorphology and Sediment Transport Laboratory
United States Geological Survey
4620 Technology Drive, Suite #400
Golden, CO 80403
Purpose
The purpose of this study was to assess the feasibility of inferring flow velocities from optical image sequences acquired from a helicopter hovering above the river by tracking water surface features via Particle Image Velocimetry (PIV) and to develop a modular workflow for performing this type of analysis. Remote sensing of flow velocity could provide a more efficient, cost-effective alternative to conventional field-based methods of measuring velocity and thus become an important component of non-contact approaches to streamgaging. Along with field measurements of flow velocity used for accuracy assessment, these data were used to assess the potential to estimate surface flow velocities in sediment-laden rivers from helicopter-based, hovering image sequences using particle image velocimetry (PIV) techniques.
Rights
Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Preview Image
Example high resolution image of the Salcha River used to perform PIV.