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Last update: May 17, 2022, at 12:58 PM
Version: pmwiki-2.3.22

Title

     OBS SURVEY 8 - 14 JULY 2016

     RV "HÅKON MOSBY"

By
O.M.
Date
02 January 2016
Version
0.1

Click to open photo album from OBS-2016 Marine Seismic Survey.

OBS-2016 Marine Seismic survey - click to open photo album.
OBS-2016 Marine Seismic Survey photo album - click to open. (Photos from similar survey in 2014.)

SURVEY, VESSEL


  • Start: 9 July 2016, Bodø
  • End: 14 July 2016, Bodø
  • Vessel: R/V "Håkon Mosby"

RV "HÅKON MOSBY" - CONTACT INFORMATION

VESSEL INFORMATION CONTACT INFORMATION
Click to visit webpage describing RV "Håkon Mosby"
  • Phone (via satellite):
    • (+47) 5590 6420
    • (+47) 5590 6423 (Bridge)
  • Mobile (bridge): (+47) 9770 1413
  • Call sign: LJIT
    To reach the vessel via VHF radio, call either Bodø or Vardø coast radio station and ask for RV "Håkon Mosby", stating vessel call sign LJIT.
    Vardø coast radio covers Barents Sea and the coastal areas from the Kola peninsula to Tromsø.

Current position:

UiB-GEO SCOPE OF SUPPLY, INSTRUMENTATION


  • Airguns: 4 ea BOLT 1500, 1200 inch3 each - total volume: 4800 inch3
  • Gravity meter
  • Mini-streamer
  • Seismic source (airgun) control system (GUNCO) including time-stamping instruments.
Click to enlarge.

Testing of Ashtech time stamping unit. PPS signal output is routed to EVENT input. Click to enlarge

Click to enlarge.

Testing of Gravity Meter. Click to enlarge.


AIRGUN SOURCE / MINI-STREAMER GEOMETRY


Overview



OBS-2014 acquisition geometry; layout of 2016 geometry expected to be identical. Download PDF version.

Airgun source


  • Number of airguns: 4
  • Model: BOLT 1500, 1200 inch3
  • Volume, total: 4800 inch3 = 79 Liter
  • Air pressure, nominal: 2000 PSI = 138 Bar
  • Source depth, nominal: 6 meter (check)

UTM Zone, reference point on vessel


All UTM data are relative to UTM Zone 32W.

All coordinates are also relative to the position of the gravity meter on board the ship.

Location of gravity meter
Gravitymeter is placed at frame 40.

Frame distance is 0.6 m. Thus, gravity meter is 40 x 0.6 m = 24.0 m from the stern.

Airguns offset distance


Airguns are positioned 43 meters behind the stern.

We have to add offset between gravity meter and stern, to obtain the total offset between source and positions given in navdata files.

Thus, total offset between source and positions given in nav data files is: 43 m + 24.0 m = 67 m.

MINI-STREAMER & SEISMIC RECORDING SYSTEM


Mini-streamer 8 channels


Click to enlarge.

Click to enlarge.

Ref streamer description.

Recording system


Mini-streamer data is recorded on Geometrics GEODE, which is controlled from a PC laptop running Windows.

Click to see Geode product description.

Click to see Geode product description.

Primary recording system:

  • GEODE 24 ch recorder:
    • S/N: 3699 --- 02/16/05 --- VER. 9.04
    • Software version: Ver 11.1.69.0 (lastest, as of 18 June 2016)
    • Power supply:
      Mfr: Traco Power
      Mod. TXL 220-12S
      Input: 100-240Vac / 47-63Hz / 3.2A max
      Output: 12.0Vdc, max 18.4A
      Supplier: Farnell
      Supplier P/N: 1242620
      Data sheet: PDF
  • Laptop:
    • HP Compaq 6710b
    • Size: 355 x 265 mm
    • OS: WinXP, Service Pack 3
  • Updated:
    • Microsoft Security Essentials - performed complete scan, no problems reported.
    • WinSCP
    • Firefox
    • TeraTerm
    • Removed unused COM ports according to instructions here.

Backup recording system:

  • GEODE S/N: 4153 --- 07/25/07 --- VER. 9.14
  • Geode software: 11.1.69.0 (lastest, as of 18 June 2016)
  • Laptop:
    • DELL Inspiron 9400
    • Size: 395 x 288 mm. Purchase new carrying case of sufficient size, from Imento.
    • OS: Win Vista, Service Pack 2
  • Updated:
    • Microsoft Security Essentials - performed complete scan, no problems reported.
    • WinSCP
    • Firefox
    • TeraTerm
    • Removed unused COM ports according to instructions here.

Time stamp recording system:

  • Laptop:
    • Lenovo Thinkpad X300
    • OS: Win Vista, Service Pack 2
  • Updated:
    • Microsoft Security Essentials - performed complete scan, no problems reported.
    • WinSCP
    • Firefox
    • TeraTerm
    • Removed unused COM ports according to instructions here.
  • Installed Geode software: Ver 11.1.69.0 (lastest, as of 18 June 2016)


TIME STAMPING OF SHOT EVENTS - OVERVIEW


The Ocean Bottom Seismographs that are deployed on the sea floor, or recorders on land, keep time using very accurate internal clocks, or GPS.

It is necessary to obtain time stamp of every shot event in order to process data later on. The time stamping is done by routing the "SCOPE TIME BREAK" from GUNCO signal to a GPS based event recorder.

The "SCOPE TIME BREAK" signal is emitted on "Zero time" - the nominal firing moment of all guns, according to the timing method that has been selected from GUNCO menus. It is emitted in sequence after two GUNCO input control signals have been asserted correctly - the CLOSURE and FIRE signal. The relationship between these three signals is shown below.


Gun Controller timing diagram.

So the falling edge of the SCOPE TIME BREAK signal is used as input for the time stamping unit.

Diagram of time stamping system - hardware and software


UiB OBS-2014 survey: Overview of time stamping hardware and software.
UiB OBS-2014 survey: Overview of time stamping hardware and software.

The Survey Computer is the master of the system. All parameters for the seismic line - start and end positions, interval between shot points are entered by the operator. When the line is activated, the survey computer takes care of the rest by issuing the necessary triggering signals to other units in the system, and generating proper log files.

Processed nav data is delivered in modified UKOOOA P1/90 format. Download the P1/90 specifications from here. In the P1/90 file, the parameters associated with a shot point is put in a single line of text, however the formatting is very compact making the identification of the individual parameters a bit difficult.

GEOMAR has established an unofficial extension of the standard to accommodate the time stamp information that OBS surveys require. These time stamps are put in record positions that are normally assigned for other purposes, but can be "sacrificed" if need be.

See more detailed explanation below.

Ashtech time stamp unit "ProFlex Lite DG14"


Click to open documentation of primary time stamping equipment Ashetch ProFlex Lite DG14.
Click to open documentation of primary time stamping equipment Ashtech ProFlex Lite DG14.
  1. Primary time stamping system, Ashtech ProFlex Lite DG14, is documented here.
  2. Back-up time stamping system is documented here.
  3. Time stamp signal used: GUNCO, BNC connector on rear panel labelled: "FTB SCOPE" (FTB = "Field Time Break"). Signal level is TTL (ca 0-5V), active low with leading, falling edge indicating Time Break (=shotpoint time).
  4. Ashtech GPS records shot events in GPS time which is currently (as of 19 June 2016) 17 seconds ahead of UTC time. Ref.:

COM port pin out


DG14 COM port pin out
Ashtech DG14 COM port pin out, from page 13 in manual.

Unit configuration


Check options installed by issuing the $PASHQ,RIO command, ref.page 15 in the manual. Here is the response:

  $PASHR,RIO,DG16,DD04,,TOPUB_LE_C__YXDR___I,71168612DG6201222026*17

Old Ashtech GG24 config


; Setup for Ashtech GG24
: ===========================
;
; Reset with default settings
$PASHS,RST
;
; Set receiver in mixed GPS/GLONASS mode
$PASHS,SYS,MIX
;
; Set elevation mask to 10 degrees
$PASHS,PEM,10
;
; Send NMEA message GGA on port C
$PASHS,NME,GGA,C,ON
;
; Send NMEA message SAT on port C
$PASHS,NME,SAT,C.ON
;
; Send NMEA message ZDA on port C
$PASHS,NME,ZDA,C,ON
;
; Set NMEA "send message interval" to 1 Hz
$PASHS,NME,PER,1.0
;
; Set event marker signal to falling edge
$PASHS,PHE,F
;
; Set 1PPS trigger edge to falling edge
$PASHS,PPS,01.00,+000.0000,F
;
; Output Event marker message on port C
$PASHS,NME,TTT,C,ON
;
; Output Signal-to-Noise-Ratio (SNR) in dB*Hz
$PASHS,SNR,DBH
;
; Output Event marker time in GPS-system-time
$PASHS,TSC,GPS
;
; Save settings in battery backed-up memory
$PASHS,SAV,Y

Configuration 8 July 2016



$PASHQ,RIO
$PASHR,RIO,DG16,DD04,,TOPUB_LE_C__YXDR___I,71168612DG6201222026*17
$PASHS,SYS,MIX
$PASHR,NAK*30
$PASHS,RST
$PASHR,ACK*3D
$PASHS,SYS,MIX
$PASHR,NAK*30
$PASHS,PEM,10
$PASHR,ACK*3D
$PASHS,PHE,F
$PASHR,ACK*3D
$PASHS,PPS,01.00,+000.0000,F
$PASHR,ACK*3D
$PASHS,NME,TTT,C,ON
$PASHR,ACK*3D

Secondary time stamping system


Documentation

AIRGUN CONTROLLER - "GUNCO"


GUNCO connector wiring


The key to understand the GUNCO connector system is to see how the front slot positions of the MSIBG cards corresponds to the connectors on the rear side - see figure below.

We normally only use one MSIBG card located in slot #5. This card will thus have sensors connected on SI3 (labelled "STBD1,2"), and solenoids on SO5 (labelled "STBD 1").

GUNCO connector principle.
GUNCO connector principle.

GUNCO rack wiring (rear view)


Current system

Click to open PDF document:


GUNCO Rack cabling. Click to open PDF version.

Old system

The difference is that relays have been added for the airgun solenoid test unit, which allows the operator to monitor sensor voltage and current, and measure resistance to solenoid.

GUNCO Sensor Display


This is what a GUNCO sensor display could look like. Click to see larger version. NOTE: Airgun no. 1,2 and 6 is OK. No. 5 has crossfeed from the solenoid pulse; the "crosfree blanking" feature of the GUNCO is activated (red area), causing any signal that appears within the read zones to be ignored.

GUNCO sensor display. Click to enlarge.
GUNCO sensor display. Click to enlarge.

SYNC UNIT


The Sync Unit is placed between the EIVA Survey computer and GUNCO. It receives a trigger command from the survey computer in the form of an ASCII "A" sent over RS232 serial line.

The Sync Unit was designed in 1998 and at that time also interfaced two other systems, a magnetometer and a recording system (DFS V) that have both been phased out long time ago. The LCD menu hasn't been updated and thus still provides options that reflects those now unused systems (so don't get confused).

At that time the Survey Computer by mistake sometimes issued double shot event triggers a couple of seconds after the proper trigger. This caused the GUNCO to fire when it wasn't supposed to. To prevent this situation the Sync Unit was furnished with a software timer that defined a period in which new triggers were ignored after the first one. The green LED on the front panel is lit during this "trigger ignored" interval.

This survey requires 12.5 meter shot point distance, which means the "trigger ignored" setting must be reduced from it's current value of approx 8 seconds, down to 1 second. This is explained in section below.

Click to enlarge:
Front view - click to enlarge.
Click to enlarge:
Inside view - click to enlarge.
Click to enlarge:
Rear view - click to enlarge.


Routing of CLOSURE and FIRE signal to GUNCO


The GUNCO is now controlled by the "Triacq" recording system of the 3km streamer. Two BNC cables must be relocated so it will become slave to the Sync Unit instead:

  1. Disconnect the coax cable bundle (consisting of three cables) from the Triacq recording system. The Triacq recording is located in rack #3 counting from GUNCO. Remove the rear wooden "door" in the corridor.
  2. Route like this:
      ---------------------------
      SYNC UNIT           GUNCO
      ---------------------------
       CLOSURE   <---->   CLOSURE
       FIRE      <---->   FIRE
                          FTB  (not needed)
                          FTB SCOPE (to GEODE recording, GPS time stamp unit)
    

Schematics


CPU card inside: "Flashlite-V25"


The CPU card is "Flashlite-V25" made by JK Micro. This product has long since been replaced by other versions. The documentation cannot be located (here's a report from someone using it in 2000). But it's quite similar to its replacement, Flashlite 186:

Flashlite 186 embedded computer made by JK Microsystem
Flashlite 186 embedded computer made by JK Microsystem.

How to alter the "trigger ignored" time parameter


The Flashlite 186 CPU card is in reality a tiny MSDOS computer. In initial mode we get contact with the card via serial RS232 cable. A terminal program will then get access to the normal DOS prompt.

A user program is automatically started by following instructions found on page 2 of the Flashlite 186 manual:

When power is applied to the Flashlite or when it is reset, the board goes through its initialization procedure and then starts DOS. A simple (read-only) AUTOEXEC.BAT file is executed and then the board is ready to use. The batch file performs several functions before the user is given control. The DOS search path is set, the DOS prompt is set, the CTRL-C flag (discussed later in this manual) is checked and finally, an attempt is made to execute a file named STARTUP on the B: drive. This provides a convenient way for custom applications to execute immediately after initialization of the Flashlite. If you wish to have your application start automatically, create a batch file named STARTUP.BAT that invokes the program.

Here is the crucial point. The program accepts command line parameters. The first parameter instructs the card to operate in either "OBS" mode (that we use now) or "DFS" mode (which is deprecated). And the second parameter sets the "trigger ignored" duration, in seconds.

So in the STARTUP.BAT file the last line will be the program name followed by two parameters, "OBS" and "8" (or close to that figure). The last parameter must be set to "1" instead. If it's omitted the program uses a default value of 15 seconds instead.

How can the STARTUP.BAT file be edited? First the program that is running on the CPU card must be terminated or prevented from starting. That can be done in two ways:

  1. Connect a RS232 serial cable (1-to-1) between laptop and 25-pin female DSUB connector at the rear of the Sync Unit. Start a terminal program on laptop (TeraTerm or HyperTerm). Comm parameters are: 9600 8N1. This is what is referred to as the CONSOLE input in the Flashlite manual.
  2. Prevent the program from starting by entering <CTRL>+<C> after resetting or powering the unit (there is a reset switch on the top, or use the rear rocker switch). After interrupting the normal start-up sequence the CONSOLE port should now issue a DOS prompt.
  3. ALTERNATIVELY: Quit a running program by sending a <Q> or <ESC> character. Important: This command must be sent on the other serial port - the one that is connected to the Eiva Survey Computer and normally only receives the trigger character <A>. After that switch to the CONSOLE serial port. Press <ENTER> to see that DOS prompt is returned. This port is 25-pin DSUB male. It is probably wired as DTE (Data Terminal Equipment) with output on pin 2 (which will be pin 3 if measured on a 25-to-9 pin adapter). So a null modem cable or -adapter is needed.

The edit process itself is described on page 15 of the Flashlite 186 manual:

EDIT.COM
A simple line editor is included to allow quick creation and modification of batch files or other text files. EDIT is similar to Microsoft’s EDLIN provided in earlier versions of MS-DOS. It allows list, insert, delete, and modify. Upon exit, a backup of the original file is created (filename.BAK) and the edits are saved. If a backup file with the same name already exists, it is overwritten. A list of commands and their usage is available by entering ‘h’ at the edit prompt ( >> ). The name of the file to edit must be supplied following the command EDIT on the command line.

 EXAMPLE:
  B:\>edit test.bat
  FlashLite Line Editor v1.0
  Enter h for help
  New File: test.bat
  >> i
  0: @echo Batch file being processed...
  1: mytsr
  2: myapp
  3: ^Z
  >> l
  0: @echo Batch file being processed...
  1: mytsr
  -> 2: myapp
  >> q
  Save before exit (Y,n): y
  File Saved
  B:\>

Here is a description of the vintage MSDOS EDLIN command line editor.

GRAVITY METER



Air/Marine Gravitymeter LaCoste & Romberg, S-99

Synchronizing SPRING TENSION values


Remember to synchronize SPRING TENSION value in software with the actual spring tension as shown on the counter on the left side of the sensor platform.

Daily log


Log sheets can be downloaded from this page: http://www.geo.uib.no/eworkshop/gravitymeter/index.php?n=Main.LogSheets

Sensor installed in vessel


  1. Remove all cushioning material used to prevent the sensor cradle from moving. At least three places.
  2. When sensor is clamped (the knurled knob turned fully clock wise) adjust the front panel meter if it's not showing ZERO.
  3. Switch on sensor by depressing two MCBs = Miniature Circuit Breakers on the power supply box, which is located behind the sensor platform (access to the right side).
  4. Perform a BEAM ZERO AND GAIN test as described on page xx of the manual. We are using L&R sensor.
  5. Start Gravity PC in instrument room. Software path: C:\ULTRASYS\ultrasys.exe

Beam Zero and Gain adjustment (L&R Sensor)


Refer to gravity meter manual.

K-check


Refer to gravity meter manual.

Base readings; land gravity meter


  1. The two Gravity base readings we performed on OBS survey in July/August is documented here.
  2. Land gravity meter is always connected to battery so the sensor temperature is kept constant at 49.5 degC. While inactive, the battery is connected to charger which is powered from 230 Vac.
  3. Ensure that 230Vac cable to charger is well protected from edges of the lid. Some cushioning material should prevent the lid from closing and thus severing the cable (fuses in vessel will then blow also).
  4. You must first adjust rotating wheel so it shows values which will be expected in Bodø - around xxxx. It was last used in. Rotate the wheel gently to avoid "upsetting" the gear mechanism.
  5. Base reading procedure:
    1. Sensor readings should be stable. TC (Total Correction) as shown on screen should be around zero.
    2. First: "Still Reading" => Write down the six fields in the sensor record shown on the computer screen: [1] Time (consisting of Day_of_year + time UTC, [2] Digital gravity, [3] Spring tension, [4] CC = cross coupling, [5] Raw = beam position, [6] TC = total correction
    3. Disconnect gravity meter from 230Vac charger. All connectors are polarized and labelled - can't go wrong. Move land gravity meter to quay beside ship. Measure distance from quay to water table surface with rope that's inside the gravity meter box. Remember to bring a tape measure. Level the meter. Unclamp the beam screw. Take three measurements, always adjusting the wheel so values are increasing. You can either look at meter, or use the ocular. Clamp the meter afterwards.
    4. Move to reference point and make three recordings.
    5. Back to same location at quay and make three new recordings.
    6. Make a new Still Reading.
    7. Reconnect gravity meter to 230Vac charger. Remember the cushioning material under the lid of the case.

Land gravimeter calibration table


Calibration table land gravimeter.
Calibration table land gravimeter L&R S/N: G-936. Click to enlarge.

Converting the counter reading to milliGals


Excerpt from p.1-9 of G-936 Instruction Manual:

  If the counter reading is 2654.32, look at the calibration table for your meter. Remember that each meter has its own unique table.

                          Portion of calibration table
     _____________________________________________________________________________
    /                                                                             \
   /    Counter reading           Interval factor           Cumulative value       \

            2500   ..............     1.00794    .............   2519.42 
    +---->  2600   ..............     1.00799    .............   2620.21  <---+
    |       2700   ..............     1.00805    .............   2721.01      |
    |       2800   ..............     1.00811    .............   2821.82      |
    |                                                                         |
    |    Divide the reading into two parts:                                   |
    |                                                                         |
    +---->  2600.00                               2620.21  <------------------+
            + 54.32                                +54.75  <----+
            -------                               -------       |
            2654.32                               2674.96       |
                                                                |
         Interval factor x reading within interval              |
                                                                |
                               1.00799 x 54.32 = 54.75  <-------+

Bodø Gravity Reference Stations


Click to follow Bodø map link, with three Gravity Stations marked. BODØ P is obsolete.

Click to follow Bodø map link, with three Gravity Stations marked. "BODØ P" is obsolete.

Gravity Station "BODØ K" Gravity Station "BODØ A"
Click to enlarge. Click to download PDF version.

Contact information:

There is also reference to "BODØ P" in the list of Norwegian Gravity Stations, with coordinates:

  • Lat: 67 deg 16.27 min => 67.271166 deg
  • Lon: 14 deg 21.90 min => 14.365000 deg

This Gravity Station is obsolete as that position is on the apron of Bodø Airport.

Gravity meter base readings Bodø


Click to enlarge.

Land gravity meter measurement.

Click to enlarge.

Bodø Gravity station "A".

Click to see all technical photos.

OBS-2016 Survey: Gravity meter base readings BODØ
Measurement 8 JULY 2016 14 JULY 2016
Still reading BEFORE
   Day-of-year / Time [UTC] ...
   Digital gravity ...
    Spring tension ...
    Cross coupling ...
          Raw beam ...
  Total correction ...
  190:09:10:00
  14048.1
  14047.1
  0.0
  -2.0
  0.8
  Screen shot
  196:06:24:00
  14045.2
  14045.5
  0.0
  -17.0
  -0.6
Quay beside ship #1
  Distance from jetty to water surface [m] ...
                          Start time [UTC] ...
               Land gravimeter, reading #1 ...
                    --"--       reading #2 ...
                    --"--       reading #3 ...
                            End time [UTC] ...
  4.0
  09:29
  5846.330
  5846.330
  5846.330
  09:33
  3.21
  06:30
  5846.335
  5846.330
  5846.330
  06:34
Gravity station
Start time [UTC] ...
           Land gravimeter, reading #1 ...
                --"--       reading #2 ...
                --"--       reading #3 ...
                        End time [UTC] ...
  BODØ "A"
  10:08
  5843.085
  5843.085
  5843.085
  10:12
  BODØ "A"
  06:54
  5843.070
  5843.070
  5843.070
  06:59
Quay beside ship #2
  Distance from jetty to water surface [m] ...
                          Start time [UTC] ...
               Land gravimeter, reading #1 ...
                    --"--       reading #2 ...
                    --"--       reading #3 ...
                            End time [UTC] ...
  4.0
  10:52
  5846.310
  5846.310
  5846.310
  10:55
  3.17
  07:28
  5846.322
  5846.325
  5846.322
  07:38
Still reading AFTER
   DoY  Time [UTC] ...
   Digital gravity ...
    Spring tension ...
    Cross coupling ...
          Raw beam ...
  Total correction ...
  Screen shot
  190:11:07:20
  14048.1
  14047.1
  0.0
  3.0
  0.8
  Screen shot
  196:07:51:00
  14045.0
  14044.2
  0.0
  0.0
  0.8

Daily log


OBS-2016-gravitymeter-daily-check-log.pdf

Click to enlarge.


PRODUCTION OF UKOOA P1/90 NAV DATA FILE


UKOOA P1/90 navdata format


Output from nav data processing should be in UKOOA P1/90 format, slightly modified to accommodate three decimals in time value.

The UKOOA P1/90 format specification can be downloaded from SEG. It's a fixed-position format without any <SPACE> or <TAB> delimiters between fields, so it can be hard to read. However, by inserting appropriate comment field in the header, it can be made much more legible, as this example shows. The first part is the header; the individual shot points are at the end (six lines) :

   H0100 SURVEY AREA ISFJORDEN, SVALBARD
   H0101 SURVEY DETAILS SVALEX-2005
   H0102 VESSEL DETAILS R.V. HAAKON MOSBY
   H0104 STREAMER DETAILS 240 CH GECO NESSIE-3
   H0200 SURVEY DATE AUGUST - SEPTEMBER 2005
   H0201 FILE CREATED 16-Jan-2006
   H0202 FILE VERSION UKOOA P1/1990
   H0300 CLIENT SVALEX-2005
   H0400 GEOPHYSICAL CONTRACTOR UNIVERSITY OF BERGEN, NORWAY
   H0500 POSITIONING CONTRACTOR N/A
   H0600 POSITIONING PROCESSING O.M. UNIVERSITY OF BERGEN, DEPT OF EARTH SCIENCE
   H0700 POSITIONING SYSTEM
   H0700 SURVEY COMPUTER SOFTWARE NAVIPAC, EIVA, DENMARK
   H0700
   H0800 SHOTPOINT POSITION CENTRE OF SOURCE
   H1000 CLOCK TIME UTC
   H0900 OFFSET SHIP SYSTEM TO SP 70.0 M BEHIND
   H1200 SPHEROID AS SURVEYED A,1/F WGS-84 Spheroid 6378137.000 298.2572236
   H1300 SPHEROID AS PLOTTED A,1/F WGS-84 Spheroid 6378137.000 298.2572236
   H1400 GEODETIC DATUM AS SURVEYED WGS-84
   H1500 GEODETIC DATUM AS PLOTTED WGS-84
   H1700 VERTICAL DATUM SL : ECHO SOUNDER
   H1800 PROJECTION 001 UTM NORTHERN HEMISPHERE
   H1900 ZONE 33X NORTHERN HEMISPHERE
   H2000 GRID UNIT 1 METRE
   H2001 HEIGHT UNIT 1 METRE
   H2002 ANGULAR UNITS 1 DEGREES
   H2200 CENTRAL MERIDIAN 15 DEG E
   H2600
   H2600 00011111111112222222222333333333344444444445555555555666666666677777777778
   H2600 78901234567890123456789012345678901234567890123456789012345678901234567890
   H2600 -NAME-><->---<-SP-><---LAT--><--LONG---><--EAST-><-NORTH-><-DEP><D><TIME>-
   SLine34-05             18781022.23N 141348.31E 482384.58677774.7 215.8242180734
   SLine34-05             19781023.47N 141353.32E 482416.98677812.8 214.7242180755
   SLine34-05             20781024.73N 141358.24E 482448.78677851.4 212.3242180816
   SLine34-05             21781026.00N 1414 3.08E 482480.08677890.4 209.6242180837
   SLine34-05             22781027.28N 1414 7.88E 482510.98677929.7 207.6242180858
   SLine34-05             23781028.53N 141412.83E 482543.08677968.1 206.2242180919

UKOOA P1-90 navdata format structure.

The shot point (SP) parameter, for instance, is located from column 20 to 25, as shown below. The two column numbering lines, together with the parameter name line, is an aid in determining the column position of the different parameters. These three "legend" lines are not common - they are only inserted by the software we use to generate UKOOA P1/90 files.

  +--------> Column 20
  |
  |    +---> Colomn 25
  |    |
  222222
  012345
  <-SP->
      18
      19
      20
      21
      22
      23

Updated standard: P1/11


The P1/90 standard was updated some years ago:

We have not evaluated the new standard yet.

"OBS" modification of UKOOA P1/90 navdata format


OBS refraction surveys means that source (airguns on ship) and receivers (OBS placed on the bottom, or on land, as an extension of the profile) must maintain a common, accurate - to the nearest millisecond - time base. This is accomplished by special oven-controlled oscillators in the OBS instruments, and GPS locked clocks in land based instruments. On board the ship, the exact time of the shot point is recorded by two time-tagging systems operating in parallel (details provided in table of geophysical equipment above).

The time field in the UKOOA P1/90 format only accommodates seconds without decimals. The format has been modified to permit storage of shot times with six decimal places, of which only the three most significant decimals are used.

An example of modified file:

   H2600 FILE FORMAT MODIFIED TO INCLUDE SHOTPOINT TIME IN COLUMNS [7..19]
   H2600
   H2600 00011111111112222222222333333333344444444445555555555666666666677777777778
   H2600 78901234567890123456789012345678901234567890123456789012345678901234567890
   H2600 <--SP TIME--><-SP-><---LAT--><--LONG---><--EAST-><-NORTH-><-DEP><D><TIME>-
   SSM-1 101921.956000    99632728.92N  74033.97E 732982.37045135.6 171.3297101921 
   SSM-1 102109.690000   100632728.28N  74019.50E 732783.87045101.1 172.4297102109 
   SSM-1 102251.455000   101632728.66N  740 5.07E 732583.57045098.3 176.4297102251 

"EIVA" Survey Computer shot event log files


The format of these shot point log files is as follows:

 Event       Date         Time    Easting    Northing St.d.  Gyro      Dal    Dol      Kp    Object    Data
 -----------------------------------------------------------------------------------------------------------
 000774 2016.07.10 14:54:03.200 0648120.91 07516414.04 00.90 337.2 23356.01 -51.16 076.050 "Filtered  " 0086.72 14241.33 "" 01
 000775 2016.07.10 14:55:29.762 0648016.56 07516531.21 00.90 308.5 23506.46 -06.63 076.200 "Filtered  " 0087.11 14241.93 "" 01
 000776 2016.07.10 14:56:47.782 0647878.86 07516593.77 00.80 308.3 00104.40 -26.24 076.350 "Filtered  " 0088.52 14243.41 "" 01
 000777 2016.07.10 14:58:07.241 0647753.91 07516676.84 00.90 318.0 00254.38 -21.76 076.500 "Filtered  " 0090.26 14246.09 "" 01 

Parameters are given in first line. Most are self-explanatory, except these:

Gyro
Heading of ship (which could be different from the course the ship is following, due to current or wind direction).
Dal
Distance Along Line. NOTE: This is distance along current line SEGMENT, where new segment start at position of each OBS.
Dol
Distance Off Line (deviation from course line - we have manual steering of vessel).
Kp
Kilometer Post - total distance covered along the line.
Object
Description of Survey Computer navigation data handling. Complete text is not included in log file; it should read "H Mosby filtered", meaning that GPS positions (incl. differential corrections) are subjected to a filtering algorithm (Kalman).
Data
Data values, delineated by "", selected by Eiva Survey Computer operator; in this case Depth (from Simrad EK60 Echo Sounder on board), and Gravity.

The last item in each line ("" 01) can be ignored.

Shot time stamp files


The airgun controller (GUNCO) provides a signal that indicates when the shot was fired.

Technically, it's a TTL-level signal, normally in a HIGH state (approx 5 Volt); a short pulse of approx 100ms duration will be emitted at every shot, with the falling edge indicating the nominal shot point. Yes, individual air guns may fire a certain amount of time before or after this nominal shot point, but if this deviation is too large - in our case +/- 2 ms off target - the GUNCO will provide av audio and visible warning that the shot should be discarded.

The signal is routed to a special GPS receiver (Ashtech model ProFlex Lite DG14) furnished with a trigger input line. The trigger can be specified at falling or trailing edge of a pulse. When a trigger occurs the units transmits a record of the time stamps on one of its serial ports.

Time stamp values are NOT provided in UTC format, but in the format that is used internally by the GPS system - so called "GPS time". The difference is that "leap seconds" are inserted at irregular intervals into the UTC timing in order to keep UTC in sync with Earth's rotation (which is gradually slowing down, but not in a linear fashion), whereas GPS time is based on atomic oscillations that are unaltered over time. As of 19 June 2016, GPS is ahead of UTC by 17 seconds.

 $PASHR,TTT,1,01:34:50.6736354*0A
 $PASHR,TTT,1,01:35:04.7150736*0D
 $PASHR,TTT,1,01:35:34.7395346*06
 $PASHR,TTT,1,01:36:04.7639513*03
 $PASHR,TTT,1,01:36:34.7883658*03
 $PASHR,TTT,1,01:37:04.8127920*09

Parameters are comma delimited. Record structure mimics NMEA GPS telegram format. Using first line as example, parameters are:

Field #1 - $PASHR
Telegram header. By convention, "P" stands for "proprietary" (meaning not covered by the standard). "ASH" = Ashtech, the name of the manufacturer.
Field #2 - TTT
Time tag identifier
Field #3 - 1
N/A
Field #4 - 01:34:50.6736354
Event time stamp, in GPS time. Seven fractional digits.
Field #5 - *0A
Telegram checksum (NMEA stryle).

Software for generating UKOOA P1/90 navdata file (in "GEOMAR" format)


All scripts are written in Python version 2.7. Download Python interpreter version 2.7 from here.

Example Python software files:

Example input files:

Example output files:

   DESCRIPTION:   
   Merges information from two sources: a) The navigation files from the EIVA Survey
   computer, which holds records of Shot point (SP) number, UTM coordinates, date,
   time, depth and other parameters and b) accurate GPS based timing of each shot.

   Sequence of processing steps:

   A] The script applies an offset to EASTING & NORTHING coordinates in EIVA navigation
      file, in order to adjust for distance between seismic source and position reference
      point. Offset adjustment it based on treating shot points as vectors: First the 
      difference vector between current and previous SP is calculated. This vector is
      divided by its own length, obtaining a unit length vector. The unit length vector
      is then multiplied by the offset distance, yielding a correction vector that is
      subtracted from current SP. First SP is treated differently though, as there is no
      previous SP in that case; instead, next SP is used to obtain correction vector. 
      Idea for improvement: Use Python libs "SciPy" and "Numpy" and perform interpolation as in this example.
   B] Collect corresponding GPS time stamp from the other file. Convert GPS time stamp to
      UTC. Check that timestamps in EIVA and GPS-file differs only by a user-defined
      amount.
   C] Generate UKOOA file.

   INPUT FILES:
    Must be in same directory as this script. Name of input files stated in Constant
    section.

   OUTPUT FILE:
    Will be placed in same directory as this script.

   UKOOA P1/90 HEADER, UTM ZONE, OFFSET DISTANCE:
    See 'Constant' section.

   EXTERNAL LIBRARY USED:
    UTM to Lat/Long conversion - download library from:
       http://www.pygps.org/#LatLongUTMconversion  (no, link seems to be dead).
        LatLongUTMconversion.py download from local repository. 
        Should be replaced by pyproj module when time permits.
    Either:
    a) On Linux: Unpack it, and run "python setup.py install" as root.
       In order to build Python modules you must first install 'python-devel'.
    b) Windows/Linux: Put "LatLongUTMconversion.py" in the same directory as this file.


LOG SHEETS


DATA


OBS recording gain test 8 July 2016


Time stamps of some trial air gun shots 8 July 2016 - using primary time stamping system, in GPS time, which is 17 seconds ahead of UTC as of 14 July 2016.

$PASHR,TTT,6,13:31:52.7336251*08
$PASHR,TTT,6,13:32:52.7825148*09
$PASHR,TTT,6,13:33:52.8313595*0D
$PASHR,TTT,6,13:34:52.8802078*07
$PASHR,TTT,6,13:35:52.9290406*0B
$PASHR,TTT,6,13:36:52.9778899*01
$PASHR,TTT,6,13:37:53.0267688*0D
$PASHR,TTT,6,13:38:53.0756370*07
$PASHR,TTT,6,13:39:53.1244757*00
$PASHR,TTT,6,13:40:53.1732995*0A
$PASHR,TTT,6,13:41:53.2221656*0F
$PASHR,TTT,6,13:42:53.2709954*0E
$PASHR,TTT,6,13:43:53.3198715*0B

Profiles


LINE INFORMATION EIVA SURVEY COMPUTER GPS TIME STAMPS1)
(primary or secondary)
MINI-STREAMER UKOOA MicrOBS NAV FILES LOG SHEETS COMMENTS
ID SP INT [m] START
SP Date Time [UTC]
Easting / Northing (UTM Zone 32W)
END
SP Date Time [UTC]
Easting / Northing (UTM Zone 32W)
EVENT FILE2) 10 SECONDS LOG FILE RAW PROCESSED INFORMATION P1/90 FILES P1/90 QC FILES
P1 150 0079
09 July 2016
19:28:28
0680132.86 / 07496596.65
0336
10 July 2016
01:16:07
0713389.10 / 07475938.98
Link File A
File B
Primary Primary
  1ms/2.048s/8ch/SP=0079/FFID=973 / P1 log file / 951.SGY
Link Link Link - -
P2 150 0387
10 July 2016
03:14:14
0712767.53 / 07476359.55
0773
10 July 2016
10:48:57
0663567.40 / 07506884.25
Link Link Primary
Secondary
Primary
  1ms/4.096s/8ch/SP=0387/FFID=2078 / P2 log file / 2000.SGY
Link Link Link - -
P3 150 0775
10 July 2016
14:55:30
0648016.56 / 07516531.21
2356
11 July 2016
22:06:03
0446647.25 / 07641792.65
Link Link Primary
Secondary
Primary
  Two segments with different recording lengths:

    1ms/ 4.096s/8ch/SP=0775/FFID=3007 / P3-A log file / 3000.SGY
    1ms/10.240s/8ch/SP=1685/FFID=4000 / P3-B log file / 4000.SGY
Link Link Link - -

1) Primary time stamp system uses GPS time, 17 seconds ahead of UTC as of 14 July 2016. Secondary system time stamps in UTC.

2) Event file description:

  Event       Date         Time    Easting    Northing St.d.  Gyro      Dal    Dol      Kp    Object    Data

Raw gravity meter data


Directory with raw gravity meter data (you will normally use georeferenced data in table above, with 10s logging interval).

SCREENSHOTS


Click to enlarge.

Mini-streamer recording using Geometrics Geode. Time stamps window lower left.

Click to enlarge.

QC laptop.

TO-DO


  1. Order laptop power adapter, for Lenovo X300
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Page last modified on June 25, 2019, at 06:58 AM
Electronics workshop
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