Bathymetry and Acoustic Backscatter—Estero Bay, California

Survey Outline

The 2012 mapping mission (U.S. Geological Survey) Field Activity ID: S-05-12-SC collected high-resolution bathymetry and coregistered acoustic backscatter data from outer Estero Bay, California (fig. 1). The survey was completed in 11 days, from July 30 to August 9, 2012, and consisted of 117 survey lines covering approximately 165 km² (64 mi²) in elevations ranging from about -45 to -250 m (-148 to -820 ft) relative to the North American Vertical Datum (NAVD88).

Bathymetric surveys were completed using a RESON SeaBat 7111 multibeam echosounder. The sonar was pole-mounted on the 34-ft USGS mapping vessel R/V Parke Snavely (fig. 2 and 3). Global Navigation Satellite System (GNSS) position and inertial motion and orientation measurement data were recorded using an Applanix Position and Orientation Solutions for Marine Vessels (POS MV) 320 inertial-aided position and orientation system. The sonar head, GNSS antennae, and the inertial motion unit (IMU) were surveyed in place to a common reference frame with a Geodimeter 640 Total Station. The R/V Parke Snavely was outfitted with three networked workstations and a navigation computer for use by the captain and survey crew for data collection and initial processing. See table 1 for the sonar-system specifications.

Table 1. Seabat 7111 Sonar System specifications (Reson, Inc., 2011).
Name	Value
Frequency	100k Hz
Pulse length	0.08-3.04 ms (selectable)
Typical depth	1-900 m
Maximum Water Depth	1,000 m
Depth resolution, sector coverage,	3 cm, 150°
number of beams	101, 201 EA, or 301 ED
Along-track, across-track beamwidth	1.9° , 1.5° ± 0.05° (3.0°, 4.5°, 6.0° operator selectable)
Bottom detection method	Center-of-energy and phase-zero-crossing algorithm
Pitch stabilization	± 10° (motion sensor required)
Max update rate	20Hz (range selection dependent)
System supply	90-260 VAC 50/60 Hz, 350 W
System control	Trackball or from ethernet
Temperature–operating, storage	-5°C to +40°C, -30° to +55°C
Data output	Gigabit ethernet
Transducer array–weight	267x483x489 mm, 13.6 kg
Hydrophone and projector dimensions	636x118 mm (diameter/length)
Cable length	15 m, 30 m (optional)

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