The surveys will be carry out with instruments for bathymetrical and geophysical sounding, installed on a vessel.
The instrument system include:
• Multibeam RESON Seabat 8125, working at 455 kHz;
• Octans Surface System with gyro compass and movement sensor (MRU) integrated;
• Subbottom Profiler, Innomar SES 2000;
• DGPS Thales Landstar System with differential satellite correction;
• Software for hydrographical surveys PDS 2000.
Bathymetrical data will be obtained with the RESAN multibeam depth finder, Seabat 8125, working at 455 kHz.
The multibeam system permit to fathom the sea bottom with a variable width beam, according to depth and transducer’s aperture angle (in this case 120°).
The transducer is installed on a pile on the flank of the vessel: it is interfaced to navigation software (to visualize the data and to see the geographical reference obtained in real time), to movement sensor (to adjust rolling, surging and drift) and to gyro compass for orientation.
Before beginning surveys, the instrument will be calibrated for “static aptitude errors” caused by imperfect alignment of the transducer’s pile respect plumb-line.
Further calibration of instrument will be performed by means of measurement of sound’s speed profile in the water (achieved with Reson SVP/14 probe). This profile permit to identify with high precision and resolution the water depth. The system in this way adjust the depth looking on changing in transmission speed of acoustic waves in different water layer. The measurement of the depth obtained in this way has highest precision.
The positioning of vessel will be performed by DGPS Thales LandStar System, with differential satellite correction. The system is interfaced to PDS 2000 navigation software.
In addition to survey of bathymetrical data, Multibeam permit to obtain information about bottom morphology.
Data processing modality follows this steps:
• Correction of all bathymetrical data for tidal excursion detected;
• Editing of navigation lines for possible problems related to positioning jump or Multibeam’s errors;
• Creation of bottom digital model;
• Drawing isobaths at regular gaps of depth;
• Editing of isobaths;
• Creation of tridimensional bottom model.
The vessel is the “SIGMA I” mod. ARVOR 215, length 6.85 m, width 2.54 m, draft 0.75 m.
Topographic and bathymetrical surveys will be realized with the following instrumentation system:
• Geodesic differential satellite positioning system, constituted by couple of GPS RTK receiving equipped with Radio Link with real time correction of positioning (All A);
• High resolution bottom detection system Multibeam;
• Subbottom profiler system for geomorphologic bottom surveys (All C);
• Navigation and processing software PDS 2000 (All D).