SURVEY METHODOLOGY - PIPELAYThe HIL

SURVEY METHODOLOGY - PIPELAY
The HILONG 106 will be primarily positioned by the standard offshore positioning
system consisting of Veripos LD4/ LD3 DGPS, Meridian Surveyor gyros and DMS-05
MRU aided by accurate offset measurements.
All the survey sensors will be interfaced to NaviPac navigation suite for a
comprehensive real time positioning solution. The HILONG 106 will be running
NaviPac suite operating in Barge Management System (BMS) for anchor operations.
The Fix point during the pipe lay will be the Beadstall / Line-Up Station offset for the
HILONG 106
The AHTs will be positioned by Hemisphere combined GPS and heading system fed
with RTCM GPS corrections from the main vessel (HILONG 106). All AHTs will have
NaviPac suite operating in Tug Management System (TMS).
BMS and TMS are NaviPac’s internal rig/barge move modules. NaviPac BMS/ TMS
enables simple barge/rig management through centralised command control by
barge master via remotely controlled tug navigation displays. NaviPac’s multiplexer
telemetry enables two way position data relay between the HILONG 106 and its
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AHTs. Communication to and from Barge and AHTs will be set up via Trio ER450
radio link.
Planning and designing of anchor pattern will be carried out by the barge master by
utilising NaviPac Helmsman display that allows quick step target placement,
coordinate measurement and range/bearing to destination. These anchor patterns
will be then transferred in real time to the designated AHT as targets on the navigation
display. Surveyors stationed in the barge control room/ bridge will be monitoring and
updating the online navigation anchor status based on the communication to and from
barge master and AHT captain. An in depth anchor log will be maintained
autonomously by NaviPac’s RigMon and manually by the surveyor’s log.
In the case of the HILONG 106 structures the pile guide centre will be the primary
offset required.
In the case of the DLB01 for Tie- In and Riser Installation Centre Stern centre will be
the primary “fixing point”.
Offsets to a marked central location (CRP) on the ROVis the forward bumper bar.
Vessel offset measurements shall be taken using the standard NaviPac conventions
as noted below:
+X is to Starboard
+Y is to the Forward
+Z is Up Water depth is +ve relative to CRP
Offset measurements will be carried out utilising total station and tape measure. The
offsets will be measured independently by two (2) surveyors and also compared to
previous vessel offset diagrams.
Full details on the methodology required for obtaining a sound velocity profile refer to
the SOP-008 Sound Velocity Procedure.
The sound velocity profile unit will be wet tested during the mobilisation, by deploying
the unit to self record the sound velocity reading during down cast and up cast.
8.8.5 ROV
ROV Gyro calibration shall be carried out using the ROV offset measurement method in
accordance with SOP-003 Gyro Calibration and Verification Procedure and results
recorded using MSF-049 Gyro Calibration Record.
The ROV Gyro Calibration would only merit conducting if a precise Gyro Instrument is
included.