Data Acquisition and Processing Report (DAPR) - Center for Coastal ...

emoved remaining fliers, as well as down-sloping beams where the survey lines crossed
over the reef escarpment providing unreliable soundings.
The Hips Subset Editor and BASE surface creation were the second phase of
editing. Subset editing enabled the hydrographer to evaluate each swath against its
neighboring swath while identifying potential tidal and motion artifacts. The verification
and alignment of features from adjacent lines also confirmed sensor offsets. BASE
surfaces were created to illustrate adequate sonar coverage and to also identify systematic
errors or artifacts within the data set. The Bathymetry Associated with Statistical Error
(BASE) surfaces created from the merged and TPE calculated soundings are georeferenced
images of a weighted mean surface. The BASE surface uses a combination of
range, uncertainty and swath angle weights to assign nodes depth values to create an
image of the seabed surface. The BASE surface images were reviewed with multiple
resolutions, sun angles, sun azimuths and vertical exaggerations. The BASE surface
routine produced images representing depth, shoal-biased depth, deep-biased depth, mean
depth, standard deviation, sounding density, and depth uncertainty. During acquisition in
the field editing steps were expedited to create BASE surfaces to confirm adequate
multibeam coverage for each survey area and to identify ROV transects. The contract
Lead Hydrographer completed final processing of the datasets after field operations. This
included the re-application of sound velocity profiles adjusted by Reson B.V. to try and
compensate for beam steering inaccuracies and the application of final tides. Refer to
Appendix F for a multibeam processing flow chart. The following two images depict the
areas surveyed by the BASE depth surface.
Fig 4: 2009 bathymetry coverage, 20 km 2 , shown as 8m grid, SE of Isla De Culebra, E Puerto Rico.
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