Reson Seabat 8101

Options and UpgradesThe survey procedures for the collection of multibeam bathymetry and sidescandata are different. For multibeam bathymetry, the transducer should ideally belocated high above the seafloor so a wide swath can be measured. For bestsidescan measurements, the transducer should ideally be close to the seafloor,looking out sideways, measuring the reflection from a low incident angle. Becauseof these varying survey procedures, a decision should be made as to therequirements of the survey, and one of the techniques compromised accordingly.Remember that the SeaBat 8101 has a 150 degree field of view and surveyingvery close to the bottom will reduce the coverage area.4.5.4 Technical DetailsThe bathymetry and sidescan data are independent, both in the beamformingprocess and in how the output data are used. A separate set of processing logicis used for sidescan.• Sidescan beamforming ("old") - The sidescan beams are formed by using aprocess similar to that used for the bathymetry beams. The signals from eachelement used are amplified, weighted and summed. The difference betweenbathymetry and sidescan beamforming is that the phase adjustment for eachelement is not done. With the circular receive array, this results in a receivebeam width covering approximately the same angular sector as the elementsused to form the beam. The imagery information is contained in the amplitudedata.• Sidescan beamforming ("new") - The "new" process combines one half ofthe bathymetry beams (beams 0 to 49 for port and beams 51 to 100 for starboard)into two sidescan beams. The process combines adjacent pairs ofbeams by averaging and then combines the averages by selecting the brightestpoints from the averaged beams. The combination process uses peakdetectdetermination. The "new" process yields a less noisy output.• Sidescan data output - The array of intensity values is a series of amplitudes,one for each sample interval for each sidescan beam. The SeaBat8101's sampling rate of 5000 samples per second provides approximatelyone measurement for every fifteen (15) centimeters of range. The number ofintensity values reported in a sidescan packet is a function of range: at a 300meter range setting, using a 1500 meter per second sound velocity, thepacket will have 2000 values for each sidescan beam; at a 1000 meter range,6666 values would be output per sidescan beam. The data are output in aseries of binary packets via a network connection. These packets are separatefrom the bathymetry packets, although they are output over the samenetwork link. The receiving program must accept the packet over the networkand properly interpret it. The packet includes the time of the ping used togenerate the data (only if a UTC input is provided), which beam the data isfrom, an array of sidescan data values and other supporting information.______________________________________________________________________SeaBat 8101 Operator's Manual 4-6 Version 3.02