DATA ACQUISITION – SINGLE-BEAM BATHYMETRY
Differentially Corrected Navigation and Motion
The GPS base station was assembled at the pre-existing National Geodetic Survey (NGS) Benchmark BH08 at Point Cadet, Miss. (fig. 5.). GPS receivers recorded the 12-channel full-carrier-phase positioning signals (L1/L2) from the satellites via the Thales choke-ring antenna. This GPS instrument combination was duplicated on the survey vessel (rover). The base receiver and the rover receiver recorded their positions concurrently at 1-second (s) recording intervals throughout the survey period. Boat motion was recorded at 50-millisecond (ms) intervals using a Teledyne TSS Dynamic Motion Sensor – 05 (TSS DMS-05) (table 1).
Aboard the RV Streeterville, depth soundings were recorded at 50-ms intervals using a Marimatech E-SEA SOUND 103 echosounder system with dual 208-kilohertz (kHz) transducers (fig. 5) (table 2). The single-beam bathymetry was acquired using HYPACK® version 10 (HYPACK, Inc.), a marine surveying, positioning, and navigation software. Data from the GPS receiver, motion sensor, and fathometer were streamed in real time to a laptop computer. HYPACK acquisition combines all input data into a single raw data file, with each device string referenced by a device identification code and time stamped to the nearest millisecond. The software also manages the planned-transect information, providing real-time navigation, steering, correction, data quality, and instrumentation-status information to the boat operator.
Sound velocity measurements were collected using an Applied Microsystems Smart sound velocity profiler (SVP). The average measurement for the survey was 1,524 meters/second (m/s).