Positioning and Navigation

The Navigation system NAVPRO V5.6 by Communication Technology of Cesena was used. The positioning sensor was the FUGRO 3000L 12 channel GPS receiver, with a OMNISTAR DGPS Satellite link by FUGRO. The integrated system used a Robertson model Skr82 gyrocompass, and was used for navigation and sensor data logging, other than for the fixed distance seismic shot control.

The instrumental offsets are presented in Tab. 1 and in Fig. 9.

Table 1: navigation offsets (m) on R/V Urania for NAVPRO. Positive directions are X:starboard, Y:ahead, Z:up. Point of ZERO offset VESSEL (0,0) is located on the ship's main mast behind the command brifge. POS1 = primary positioning system of main GPS antenna.

WHAT	X	Y	Z asl
VESSEL Zero Offset	0.00	0.00	0.00
POS 1 ANTENNA	1.40	4.80	15.0
ECHO 12	-1.85	5.50	-3.50
ECHO 33	1.85	5.50	-3.50
CHIRP	-0.95	-5.50	-3.50
MAG	-3.90	-240.0	3.0
GI-GUN ARRAY	3.90	-50.0	-6.0
ACTIVE 1	0.00	-110	-10.0

figure

Figure 9: Instrumental Offsets on R/V Urania for cruise V2002

The water depth was measured by two ATLAS-KRUPP DESO 25 (the speed of sound was set to 1500 m/sec). The total magnetic field was measured by a model G-811 GEOMETRICS proton-precession magnetometer, deployed at a depth of 3 m.

The model ADU-2 ASHTECH attitude measurement system and models OS-75 and WHM-3000 RDI ADCP current meters provided additional high quality positioning data, such as heading and speed, that were recorded on separate logging systems.