Evaluation of Arctic Multibeam Sonar Data Quality Using Nadir Crossover Analysis and Compilation of a Full-Resolution Data Product

Ashton Flinders
Master of Science Defense


Monday, Apr. 7, 2014, 3:00pm
Chase 130

We document a new high-resolution multibeam bathymetry compilation for the Canada Basin and Chukchi Borderland in the Arctic Ocean–United States Arctic Multibeam Compilation (USAMBC Version 1.0). The compilation preserves the highest native resolution of the bathymetric data, al- lowing for more detailed interpretation of seafloor morphology than has been previously possible. The compilation was created from multibeam bathymetry data available through openly accessible government and academic repositories. Much of the new data was collected during dedicated map- ping cruises in support of the United States effort to map extended continental shelf regions beyond the 200 nm Exclusive Economic Zone. Data quality was evaluated using nadir-beam crossover-error statistics, making it possible to assess the precision of multibeam depth soundings collected from a wide range of vessels and sonar systems. Data were compiled into a single high-resolution grid through a vertical stacking method, preserving the highest quality data source in any specific grid cell. The crossover-error analysis and method of data compilation can be applied to other multi- source multibeam datasets, and is particularly useful for government agencies targeting extended continental shelf regions but with limited hydrographic capabilities. Both the gridded compilation and an easily-distributed geospatial PDF map are freely available through the University of New Hampshire’s Center for Coastal and Ocean Mapping (ccom.unh.edu/theme/law-sea). The geospatial pdf is a full resolution, small file-size product that supports interpretation of Arctic. 


Ashton Flinders has B.S. degrees in Chemistry and Applied Physics from the University of Wisconsin at River Falls, and an M.S. degree in Geophysics from the University of Hawaii at Manoa. His research at the University of Hawaii focused on a gravity survey of the islands of Kauai and Niihau (Hawaiian Island Chain) that he conducted between May and September of 2008. He also partook in a one-month research cruise in September of 2007 to study the variation in the gravitational field around the two islands. He integrated these new surveys with a past land survey of Niihau, and four additional marine cruises. His research revealed two positive residual gravity anomalies, one over Kauai’s Lihue Basin, the other offshore between Kauai and Niihau. These highs indicate a local zone of high-density crust that Ashton attributes to olivine cumulates in a solidified magma reservoir. Offsets between both island's residual gravity highs and their previous presumed geologic centers indicate that the islands were much larger and more asymmetric than previously thought. Furthermore, he performed geophysical inversions on the residual gravity data to estimate the volumes of the magma chambers beneath each island. He combined his gravity work with previous geochemistry and geological mapping done on the islands in order to explain the islands early evolutionary history.