Navigation, Chirp SBP, Swath Bathymetry, Single Channel Reflection Seismic

The vessel was set-up for data acquisition and navigation with PDS-2000 software by RESON, interfacing by a multiserial and Ethernet link several instruments, among them the DGPS (Fugro), the Atlas-Krupp Deso-25 single-beam echosunder, the MAHRS MRU and the meteorological station. The position and depth data were also distributed to the CTD data acquisition console. A Kongsberg processor running the SIS software, collected the multibeam data, including a SEAPATH MRU, compass, and DGPS. The MBES was the 70kHz, 400 1x2°  beams, 150°  aperture EM-710 (2000 m range) model by Kongsberg. The sonar head is positioned on the ship's keel using a V-shaped steel frame. A Sound Velocity probe at the keel 1m above the Sonar Head is interfaced directly to the MBES processor, thus providing the necessary real-time data for the beam-forming. CTD casts were normally used for input of the sound velocity profile to the system. An Anderaa Meteorological Station was also made available, at a rate of one measurement every 5 minutes.

Table 4: Instrumental Offsets on Ship Urania (EM710). The DGPS antenna (primary positioning system) is located on point SEAPATH_GPS.

POSITION	ACROSS	ALONG	HEIGHT
REF. POINT	0.00	0.00	0.00
SEAPATH_GPS	-4.039	0.163	-18.211
MRU	-0.341	-1.342	-1.596
MBEAM_TX	0.0936	10.2964	5.0623
MBEAM_RX	-0.0031	11.0144	5.0600
SEALEVEL	0	0	-0.0875

The SIS (EM-710) was able to build real-time DTM at the resolution of 2 and 1 m during the acquisition of the entire surveyed areas. The data from these production DTMs were exported and used for planning and update of the SIS projects. The raw data were instead saved in the Kongsberg's .all format, for postprocessing with packages like NEPTUNE or MB-SYSTEM or other. The processed data will therefore be used for an up-to-date regional and local bathymetric compilation.

A Teledyne Benthos CHIRP-III SBP system (16 hull-mounted transducers) was used. The data were acquired by the SWANPRO software by Communication Technology, with direct interfacing to the DGPS, therefore actual positioning data have to be converted according to the offsets of Tab.4. The data were recorded in the XTF format and converted also into the SEG-Y format for processing with ISMAR's xtf-segy and segy-change (G.Stanghellini, personal communication) and processed by the ISMAR's SEISPRHO package [Gasperini & Stanghellini(2009)]. The system setting was: length 5-10 ms, trigger rate varying from 0.125 to 0.5s,gain 9dbm preamp gain ranging from 1.5 to 3 db. Power to the transducers and gains were set in order to obtain non-clipped returns.

A GEORESOURCE SP1000 Sparker was utilized. The source and hydrophone streamer were towed from the starboard and port sides at a distance of aproximately 15m from stern. The output power at source was set at 1KJ, while the shot time ranged between 1.05 to 1.10 s.

Figure 12: Plankton sampling.