Page 147 - Acquisition and Processing of Marine Seismic Data

138 2. MARINE SEISMIC DATA ACQUISITION

TABLE 2.12 Computed (C) and Observed (O) Values of DGPS Antennas for DGPS Verification

C O C-O
Easting Northing Easting Northing Easting Northing
DGPS1 359385.42 4534585.65 359385.14 4534585.42 0.28 m 0.23 m
DGPS2 359384.03 4534586.05 359384.72 4534586.89 0.69 m 0.84 m

TABLE 2.13 Computed (C) and Observed (O) Values of rGPS Pods for rGPS Check

C C-O SD
Easting Northing Easting Northing Easting Northing
T101 pod 359375.23 4534580.55 0.18 m 0.28 m 0.10 0.16
T102 pod 359378.56 4534586.72 0.24 m 0.14 m 0.14 0.21
T103 pod 359377.86 4534585.46 0.07 m 0.18 m 0.08 0.09
T104 pod 359374.34 4534584.17 0.19 m 0.34 m 0.23 0.17
A201 pod 359380.14 4534582.13 0.28 m 0.11 m 0.08 0.10
A202 pod 359381.43 4534585.25 0.11 m 0.24 m 0.15 0.16
D301 pod 359379.24 4534581.73 0.18 m 0.14 m 0.18 0.20
D302 pod 359377.33 4534584.66 0.22 m 0.21 m 0.16 0.11

SD represents the calculated standard deviations.

measurement errors of both transducers are velocimeters, speed logs and compass birds,
calculated separately and entered as correct are performed to ensure that they are all
draught value (C-O) into the dedicated functioningproperly.Mostofthesedevicesuse
bathymetry software (Table 2.14). their internal battery packs, and they must be
checked and replaced before the survey, if
g. Control of streamer steering and acoustic devices: necessary. Wing reset and compass read tests,
A completecontrol and check of the navigation aswellasdepthreadings,areperformedonthe
instruments attached to the streamers for external steering devices and depth levelers. In
steering and positioning, such as streamer some cases, depth sensors need to be
steering devices, acoustic ranging units, recalibrated before the survey.
2.6.1.2 Tests for Seismic System and
TABLE 2.14 Computed (C) and Observed (O) Values Streamer
of Depth Measurement for Echosounder Verification
Several tests on the seismic system, and espe-
cially on the circuitry of A/D converters or dig-
C O C-O
38 kHz echosounder 15.05 m 8.13 m 6.92 m itizing modules, data telemetry and the
hydrophone elements, are performed before
200 kHz echosounder 15.45 m 7.80 m 7.65 m
the survey. Results of the seismic system and