Multibeam Surveys for Dredging Assessment
As part of a dredging project to expand the turning basin and channel at the U.S. Coast Guard Station in South Portland, Maine, Substructure conducted multibeam survey operations prior to the start of the dredging project (December 2009) and again soon after completion of the project (March 2010) with custom-built survey vessel Orion. Throughout both survey periods, Substructure set-up a Trimble R7 dual-frequency global positioning system (GPS) receiver over an established survey mark to provide real-time kinematic (RTK) differential GPS (DGPS) correctors to the survey vessel to ensure the high resolution vertical and horizontal accuracies (cm-level) necessary to confirm completion of the dredging project and to accurately compute final dredging volumes.
Final multibeam data deliverables included a 0.5 foot gridded multibeam dataset, QA/QC information, a variety of thinned data products, and final pre- and post-dredge survey drawings. Final dredging volumes were developed based on the before-dredge and after-dredge multibeam surfaces and were computed using both HYPACK and AutoCAD to verify the consistency of the results.
