Notes

 

1.    There is no documentation for the procedures for the watch to start a seismic line.  The following basic steps must be done:

A.   Determine what state the Spectra system is in.

i.        Confirm the waypoints (LMN) (Use line control and edit if necessary).

ii.      Check the shot spacing. 

iii.     Confirm that the shot numbers are correct.

iv.    Also confirm the shot point numbering on the display screen.

v.      Determine if Spectra starts the line or if it should be enabled manually later (due to daylight or depth).

B.   Setup the Syntron recording system.

i.        Cycle

ii.      Start line

iii.     Check tape number and accept.

iv.    Set to external trigger.

C.   Setup the tape label machine.

i.        Type N and enter the new line name.

D.   Setup the Seisnet computer.

i.        May have to kill the previous line.

ii.      Enter the directory name.

iii.     Execute the program.

iv.    Check itÕs in automatic mode.

E.   Setup the Sioseis real-time brute stack by:

i.        Start the init_seisnet script

ii.      Start the stack script with the line-name and plot direction.

iii.     Start the Atlantek plotter AFTER the first stack trace has been produced.

F.    Make sure thereÕs 2000psi at every shot.

G.   Make sure the LDEO navigation block is getting to Spectra (see below).  The Syntron screen displays Ò>>>>>>Ó for the shot number when it doesnÕt have a nav. Block.

H.   Enable the Watch Log.

I.      Initiate the tape copy script with a new file name for the UWYO raid.

 

2.    If Spectra starts the line (shooting) when the ship reaches a particular waypoint, the Òlog spectraÓ program fails to negotiate with the LDEO real-time navigation system.  Spectra must be disabled and enabled before the Syntron recording system gets the navigation block.  The Sioseis real-time stack requires the navigation and may have to be stopped and restarted if this happens.  The problem does NOT occur when shooting/Spectra is ÒenabledÓ AFTER the ship is past the Spectra Òstart of lineÓ.

3.     The Seisnet computer program froze several times when starting a new line.  Ethan had to be called when this happened.

 

 

Real-time Processing Problems

 

1.     The Seisnet computer should write to the same directory all the time. 

The seisnet computer writes every shot to a directory on another computer (grampus) via NFS.  Currently the disk is limited in size and must be cleaned periodically or else it fills up and the real-time processing stops.

            Determining when the disk is filling up and what shot files need to be removed is painful.

 

Navigation Notes

 

         The ship is steered by the autopilot during shooting.  The autopilot is fed either by the Instar program or the bridgeÕs Trimble NT300D GPS.  The feed is controlled by a switch on the bridge and is normally set to Instar.

         The Instar program is fed by GP01.  The feed to GP01 at any given time is known by the Science Officer only.  I donÕt know where the wires or connectors are.

         The Spectra program controls the shooting. All the different gpsÕ seem to feed into Spectra, including the bridgeÕs Trimble NT300D.  How it determines which to use is a mystery.  The location of some or all the receivers were entered into Spectra by someone sometime, presumably including the WAAS.

         There are four GPS navigation systems on the ship:

Trimble Tasman Y-code Ð the antenna is located on the A-booth.  GP01

Trimble NT300D used by the bridge Ð antenna on the mast.  This is GP02.

WAAS Ð antenna on the A-booth.  This was GP01 at the end of the cruise.

                  This is a brand new (like EW0207) system.

POS/NAV Ð Might be used by Hydrosweep, located on the new mast on the

                  bridge deck, but is corrected to the ÒshipÕs reference pointÓ.

 

         The various screens around the ship showing the current position, both GP01 and GP02, the speed, course, depth, etc. are created by a computer (and program) in the Science OfficerÕs area.  The labeling is totally at his discretion and may not relate to actuality.

         During this cruise GP01 was the Tasman receiver until it failed.  During the several days while the Tasman was flakey, it is difficult to determine what GPS system fed the various systems.  The wires to the A-booth GPS were severed by the engineers twice while they were replacing the A-booth air-conditioning unit. The WAAS system eventually replaced the Tasman as the feed to GP01.

         The offset parameter in Spectra is NOT the antenna-gun offset.

         TS.n files are created from GP01, Tasman or WAAS, which are both on the A-booth.  When the wires were cut to the A-booth I suspect GP02 was used.

         Spectra creates the UKOOA P1/P2 files as well as the real-time navigation passed back to the LDEO SpectraLog program which is then inserted into the SEG-D headers (90% confidence).  Therefore, I think both the UKOOA and real-time navigation are corrected to the shipÕs reference point.