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OBS Survey 2003 Western Norway

University of Bergen Department of Earth Science Allé gt. 41, N-5007 Bergen, Norway Rev.: 23 October 2014

The project had participants from these institutions:

• Institute of Seismology and Vulcanology, Hokkaido University, Japan
• Geomar, Kiel, Germany
• Department of Geology, University of Oslo, Norway
• Department of Earth Science, University of Bergen, Norway

The survey was conducted from May 20 to June 30, 2003, using University of Bergen research vessel RV Håkon Mosby.

This web page is a revised edition of the original site.

DATA, LOG FILES, FORMAT DESCRIPTIONS

Data and log files

Table 1: Data, log files

Note ¹⁾:

Note ²⁾:

• Link to Gravity meter base reading description.
• Link to OBS Line 3 Deployment, Recovery, Time readings, Disassembly log sheets.

Format description Survey Computer (EIVA) log files

Shot (= Event) files; format example:

004105 20:19:49 0711074.16 07809167.80 01.00 160.0 00969.12 -06.23 141.600 Filtered 2490.80 52816.00 12683.04

  Field no.   Example      Parameter              Notes
  ---------------------------------------------------------------------------------------------------------------------------------
   1          004105       Shot (event) number 	 
   2 	      20:19:49     Time                   Survey computer time not accurate - could differ by more then 10 seconds from UTC.
   3 	      0711074.16   UTM Easting 	          Referred to antenna position in mast.
   4 	      07809167.80  UTM Northing 	  Referred to antenna position in mast.
   5 	      01.00        Standard deviation
   6 	      160.0        Gyro compass reading
   7 	      00969.12     DAL                    = Distance along line [m]
   8 	      -06.23       DOL                    = Distance off line [m]
   9 	      141.600      KP                     = Kilometer post
  10 	      Filtered                            (check)
  11 	      2490.80      Depth                  From EK500 Echo Sounder
  12 	      52816.00     Magnetometer           (Length of mag tow fish cable - check!)
  13 	      12683.04     Gravity meter          (check - filtered, raw??)

Table 2. Shot (event) file format description.

Logging of depth, gravity- and magnetometer data every 10 seconds; format example:

06:21:59 23.05.2003; 553674.1175;6744618.7726; 060°49.995410'; 003°59.234563'; 326.2000; 12008.8500; 50667.0000

  Field no.   Example              Parameter      Notes
  ---------------------------------------------------------------------------------------------------------------------------------
    1         06:21:59             Time           Survey computer time not accurate - could differ by more then 10 seconds from UTC. 
    2         23.05.2003           Date
    3         553674.1175          UTM Easting    Referred to position of crane used to deploy the OBS.
    4         6744618.7726         UTM Northing   Referred to position of crane used to deploy the OBS.
    5         060°49.995410'       Latitude
    6         003°59.234563'       Longitude
    7         326.2000             Depth          From EK500 Echo Sounder
    8         12008.8500           Gravity        (check - filtered, raw??)
    9         50667.0000           Magnetometer   (Length of mag tow fish cable - check!)

Table 3. 10 second interval log file format description.

Logging of OBS deployment positions, example:

   Event 00001 Wednesday, June 11, 2003 07:47:27 MANUAL 
  Message: OBS72
  Cycle at 0.740 Gyro 320.35 Roll 0.00 Pitch 0.00 Heave 0.00 SOG 0.08 COG 63.78
  LOP  Code System                Measurement   Converted    Error    Wgt
  --------------------------------------------------------------------------------
   0      1 GPS1 (NMEA): Seapath   558940.057   558940.081   0.152   1.00
   1      1 GPS1 (NMEA): Seapath  7640272.663  7640272.614  -7.836   1.00
   2      1 GPS2 (NMEA): Trimble   558933.681   558933.768   0.918   1.00
   3      1 GPS2 (NMEA): Trimble  7640292.477  7640293.055   2.864   1.00
   4      1 Gyro: User Defined g      320.350      318.984 315.637   0.00
  Position        Easting     Northing   Height    S.td   Data
  ---------------------------------------------------------------------------------
  1        :   558940.410  7640277.937     0.00    5.36
  Filtered :   558939.738  7640277.812     0.00   -1.00    - 
  Kran     :   558937.809  7640273.477     0.00    0.00    -
  EK500    :   558934.193  7640279.616    -1.00    0.12   D 2995.50   B  1.00 
  input 1: :   559071.664  7640127.033     0.00    0.72   D 56013.00  B  0.00
  input 2: :   558940.410  7640277.937     0.00    0.39   D 12534.17  B  0.00

• Some navigation related abbreviations: LOP = line of position, SOG = speed over ground, COG = course over ground.
• The LOP's listed (0..4) are the positioning devices used in UTM coordinate calculation. Data from each unit has a certain weight (Wgt) in the calculation.
• The OBS is deployed from a crane; it's position is given in the "Kran" line.
• EK500 is depth data, input 1 is magnetometer data (not valid as it is not in operation during OBS deployment) and input 2 is gravitymeter data (should be discarded, like mag data).

INSTRUMENTATION

Block diagram

Fig. 1. OBS-2003 Survey Instrumentation block diagram.

Airgun source layout, signature, spectrum

Click image below to download pdf version.

Fig 2: Airgun source layout, signature, spectrum. Click to download pdf version. Software used: NUCLEUS, by PGS.

NOTES

ASHTECH GPS, used for timestamp of GUNCO FTB.

Ashtech GPS had to be reconfigured at start of survey. Use the Ashtech Evaluate program - there are two directories, "evaluate1" that holds unzipped main file, ready to be installed, and "Ashtech Evaluate" that is copied from already installed version (the latter may or may not work if it is just copied to a new PC).

Send these commands to the GPS (a modified version of this config file):

  Command                       Description
  -------------------------------------------------------------------------
  $PASHS,RST                    Reset with default settings
  $PASHS,SYS,MIX                Set receiver in mixed GPS/GLONASS mode
  $PASHS,PEM,5                  Set elevation mask to 5 degrees
  $PASHS,NME,RMC,C,ON           Send NMEA message RMC on port C
  $PASHS,NME,PER,1.0            Set NMEA "send message interval" to 1 Hz
  $PASHS,PHE,F                  Set event marker signal to falling edge
  $PASHS,PPS,01.00,+000.0000,F  Set 1PPS trigger edge to falling edge
  $PASHS,NME,TTT,B,ON           Output Event marker message on port B
  $PASHS,TSC,GPS                Output Event marker time in GPS-system-time
  $PASHS,SAV,Y                  Save settings in battery backed-up memory

If this GPS should fail: Use the GUNSTAMP system (ask Trond S.).

TeraTerm terminal program - for setup of OBS

This terminal program permits 600 bits/second datarate, this is not common in other terminal programs. Download from TeraTerm homepage.

Status web page with ship position, 24h track line, OBS positions and weather information

Fig. 2. Web page showing ship's position, 24h track line, OBS positions and data from Aanderaa Weather Station.

The map showing ship's position and past 24 hour track line is updated every minute. The weather station graphs are updated every 10 min. The web page itself is refreshed every 30 sec. More information on this software:

• A description of how to put data from Aanderaa Weather Station on a webpage.