TSS440 Online OOS Procedures-Rev3

DeepOcean Subsea Services Ltd. Doc. Reference UK.SUR.WP.003 8 Whiting Road Tel +44 (0)1603 622 088 Revision A3 The Norwich Business Park Fax +44 (0)1603 624 774

Date September 2008 Norwich, NR4 6DN Email [email protected] United Kingdom

DeepOcean Ltd/B.V. Online Procedures

Out of Straightness Surveys with TSS440 Pipetracker

UK.SUR.WP.003 – Rev. 3 September 2008

Title: DeepOcean Online Procedures

Subject: OOS with TSS440 Procedures

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DeepOcean Online Procedures OOS with TSS440 Procedures – September 2008

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Revision Sheet DeepOcean Project Reference Number Client Reference Number UK.SUR.WP.003 Project Location/Vessel

A3 Sept 2008 Incorporation of DigiQuartz Driver JTu RCo A2 Sept 2008 JTu RGr A1 May 2007 JTu RGr

Revision Date Revision Description Prepared QC Check Approved



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CONTENTS 1 Introduction..............................................................................................5

2 Equipment ................................................................................................6 2.1 DVL..................................................................................................................... 6

2.1.1 DVL-Qinsy Database Setup ....................................................................................6 2.1.2 DVL Calibration........................................................................................................7

2.1.2.1 Qinsy Dead Reckoning Calibration Module (from Qinsy Knowledge Base).........7 2.1.3 Qinsy Online Setup for DVL..................................................................................11

2.1.3.1 Computation Setup ...........................................................................................11 2.1.3.2 Prediction Setup................................................................................................12 2.1.3.3 Kalman Filter and DVL Weighting .....................................................................13 2.1.3.4 Examples of DVL Integrated Tracks..................................................................13

3 Parascientific Digiquartz Pressure Unit...............................................15 3.1.1 Basic Principles.....................................................................................................15 3.1.2 Barometric Pressure .............................................................................................15

3.1.2.1 Interface of Barometer ......................................................................................15 3.1.3 Calibrated Digiquartz Unit.....................................................................................16

3.1.3.1 Interface of Digiquartz .......................................................................................16 3.1.4 Local Gravity..........................................................................................................17 3.1.5 Mean Density Profile .............................................................................................18 3.1.6 Digiquartz Online check........................................................................................19

4 Seaking SONV3 Bathymetric Unit ........................................................20 4.1.1 Basic Principles.....................................................................................................20

4.1.1.1 Barometric Pressure .........................................................................................20 4.1.1.2 Calibrated Offset ...............................................................................................20 4.1.1.3 Local Gravity .....................................................................................................20 4.1.1.4 Output String.....................................................................................................20

4.1.2 Deepocean Bathymetric Sensor Setup................................................................21 4.1.2.1 Pre-Dive and Post Dive Seaking Procedure......................................................22

4.1.3 Seaking Bathymetric Online Procedure ..............................................................23 4.1.3.1 Atmospheric Pressure.......................................................................................23

5 Static Noise Test....................................................................................24

6 Effects of Speed on Bathymetric Units................................................24

7 TSS440 Pipetracker ...............................................................................25 7.1 TSS440 – QINSy Setup (Multi-beam Echo sounder driver) ........................26 7.2 TSS440 – QINSy Setup (Miscellaneous System).........................................28



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List of Figures Figure 2.1.1a – DVL Qinsy Database Setup ....................................................................................................6 Figure 2.1.3.1a Computation Setup ...............................................................................................................11 Figure 2.13b Filtering Setup...........................................................................................................................11 Figure 2.1.3.2 Prediction Setup......................................................................................................................12 Figure 2.1.3.3 DVL Weighting........................................................................................................................13 Figure 2.1.3.4a Online Track Comparison – SD 5..........................................................................................14 Figure 2.1.3.4b Online Track Comparison – SD 25........................................................................................14



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1 Introduction

This document details Deepocean UK / BV (hereafter referred to as DO) procedures for Out of Straightness surveys (hereafter referred to as OOS). It will concentrates on the general OOS procedures, with the use of the TSS440 pipetracker, and specific set up parameters for the Qinsy online software. Data quality for OOS should be of the highest quality, so all efforts should be made that the surveys are performed in good weather conditions and the survey equipment is working within its acceptable noise thresholds. The online surveyor should have a good awareness of the data that is being collected whilst surveying, and be able to interrupt operations if they believe that the data is of a poor quality. This data should be looked at immediately by the processing team who can analyse the data to confirm whether it is still within the specifications required. These procedures are written on the basis that all calibrations for DGPS, USBL and ROV motion sensors have already been undertaken and accepted. This document will focus on following equipment used in OOS

RDI Workhorse 1200 / 600 Doppler (hereafter referred to as DVL) DigiQuartz Pressure Unit Seaking SONV3 Bathymetric Unit (hereafter referred to as Seaking) TSS440 Pipetracker (hereafter referred to as TSS440)



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2 Equipment

This section will give detailed instructions on the setup of the DVL, Seaking and TSS440 and their interface and use within Qinsy.

2.1 DVL

The DVL is a critical part of OOS as it aids the USBL positioning enabling a reliable distance along the pipeline to be obtained online. When working correctly the ROV track should need very little smoothing. Excessive smoothing of the track stretches the data and can give a misrepresentation of the true top of pipeline versus KP. For that reason it is vital that the DVL is interfaced correctly within Qinsy and calibrated accordingly.

2.1.1 DVL-Qinsy Database Setup In the Qinsy database add the system type “Speed Log”. Then select the type of DVL that is to be interfaced. In the Qinsy database select the “RDI Doppler Bottom Track Speed (ASCII) (Active)” driver. Two observations need to be added to the DVL driver, one for speed and the other for direction. If the direction observation is of type “angle” (as it is for the RDI Workhorse), the rotation observation for the object, usually a gyro heading, as defined in the Controller object definition, is added to the angle data. If it is of type “bearing”, the direction will not be corrected.

Figure 2.1.1a – DVL Qinsy Database Setup



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Ensure that any angle C-O’s are set to zero and the scale factor is set to 1. 2.1.2 DVL Calibration

In order to obtain the best possible integrated ROV track the DVL needs to be calibrated for alignment and scale factor.

The DVL shall be interfaced to the Qinsy online navigation software. In conjunction with the Qinsy procedures for DVL calibration, the DVL shall be calibrated with reference to pipe tally data over a section of pipeline not less than 200 metres in length.

Enter the correct sound velocity of the water into the DVL unit. The Qinsy Dead Reckoning calibration routine will calculate its own scale factor and Angular

misalignment of the Doppler. The raw Doppler and Hipap tracks can be plotted in either Qinsy Line Database manager or

AutoCAD. The total distance of these tracks can be compared with that from the pipe tally data. The difference in total length can be used to calculate the scale factor to be applied to the Doppler. This should be used to confirm the results of the automatic calibration performed by Qinsy.

2.1.2.1 Qinsy Dead Reckoning Calibration Module (from Qinsy Knowledge Base) The purpose of this calibration module is to compare a node position from a QINSy computation with the position obtained by using speed and direction observations only. Usually the latter observations are output data from a Doppler velocity log. Two types of results are computed: so-called “integrated” (C-O) value (offset bias) for the Course Over Ground and (C/O) value (scale factor) for the Speed Over Ground, as well as COG (C-O) and SOG (C/O) values calculated from “start to stop” positions. Each time that the selected node position from the selected computation is updated, the position of the calibration node is computed using the previously computed Dead Reckoning position and the latest speed and direction observations. The first Dead Reckoning position is equal to the first node position from the computation after the calibration has been started, but after that, only comparisons are made.

Online Qinsy Controller – When online in Qinsy, click on the computation setup which is found in the Qinsy controller. The following is then needed.

Position Filters Setup – Do not use the speed and direction observations in the filtering of the ROV object in the calibration computation. Allow the position filter enough time to initialize properly before actually starting the calibration.

Definitions Setup – To start the Dead Reckoning Calibration and setup definitions, click on the “options menu” and then calibrations.



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Select computation and node for the reference position fixes i.e. ROV COG. Select external value to use for COG (direction observation-DVL Angle) and external value to use for SOG (speed observation-DVL Speed). Enter the a priori corrections to be used for the external observations. Define the observation period for calibration.

Observations - Press “Start” button to start the calibration. Press “Stop” button if calibration is to be ended before the observation period is over or when the end of a replay database is reached before the period is over.

In the upper list box, the following data is displayed: count, time of position update, latest COG value, latest SOG value, difference in Easting and difference in Northing between Dead Reckoning position and position from Qinsy adjustment, (C-O) for COG and (C/O) for SOG from last position increment. In the lower list box, the cumulative statistics (mean and SD) of the above mentioned data is displayed.



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Results - Apart from the start and stop positions for both the adjustment position fixes and the Dead Reckoning results (start coordinates are obviously the same) the “integrated” as well as “start to stop” calibration results are displayed on the last sheet of the Dead Reckoning calibration. The “integrated” values are obtained from all intermediate position differences (but are not just the mean of these results). The “start to stop” values are computed from the differences between the start (first) and stop (last) positions.

If the adjustment positions are along a straight line and not jumping back and forth, the “integrated” values will be the same as the “start to stop” values. If the adjustment position fixes are jumping, then the “integrated” results will not be very good. However, if the actual motion followed a bended path and the adjustment fixes were not jumpy, “integrated” values will be better than the “start to stop” results.

Use the “Save” button to dump the calibration results and the intermediate positions to file. The result file lists both the adjustment position fixes and the computed Dead Reckoning positions (in columns). The file can be used to display and/or plot the adjustment position fixes and Dead Reckoning tracks.

The “Print” button can be used to send the results and the observations to a printer (or text file). Print only the first page if only a summary page is wanted. The other pages contain the complete list with observations and intermediate COG (C-O) and SOG (C/O) values. Be sure to check the paper size.

The C-O value for the COG needs to be entered in the database as a C-O on the angle. The C-O value for the SOG needs to be entered database as a factor on the speed.



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Check Results - The Dead Reckoning calibration result file can be imported into a survey lines database using the Line Database Manager in the Qinsy program group. Open a new or existing line database (pro file), and select the “Import File” dialog. The Dead Reckoning results file is an ASCII text file with fixed columns.

The adjustment position fixes and Dead Reckoning tracks are best imported as “routes” and

can be shown in a Navigation Display and in Qinsy Mapping to create track plots. This routine can be replayed to check the calibration results. It can also be used to display the individual DVL track. If the user turns on the filter settings in replay it can also be used to see the integrated DVL / USBL track.



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2.1.3 Qinsy Online Setup for DVL By default Qinsy will not use the DVL in any of its computations. There will normally be a computation for each navigation system. Depending upon the clients requirements, the online surveyor will need to create a further computation(s) to utilise the DVL and compare to the raw Hipap generated position.

2.1.3.1 Computation Setup Create a new computation and name it appropriately i.e. “Integrated DVL”

Figure 2.1.3.1a Computation Setup Enable all systems like a normal computation. Click on the ROV object and the following screen should appear.

Figure 2.13b Filtering Setup

1. Filter Parameters – From the drop down menu select the “Kalman – 1D Constant Velocity” filter and choose a “Low” setting. The processors should replay some files to see which filter settings provide the best results, but this is a good starting point.

2. Extended Settings – Tick the speed and course observations. 3. Speed Parameters – For the “Course Value” select the angle observation from the DVL.

For the “Speed Value” select the speed observation from the DVL. Set the Speed threshold to a value which the ROV is never going to achieve to eliminate any spikes in speed data.

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3

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2.1.3.2 Prediction Setup It is also possible in Qinsy to enable prediction of the ROV track. This can be useful if the USBL is intermittent or if the client wishes to see a DVL only track. On the follow screen example the settings are explained.

Figure 2.1.3.2 Prediction Setup

1. COG / SOG Computation Parameters – select the “Angle” observation from the DVL for the “COG Value” and the “Speed” observation from the DVL for the “SOG Value”.

I have been informed by QPS that they now recommend that for COG/SOG Computation parameters to use the pull down option “Kalman Filter”. I recently replayed a file and did what they said and got exactly the same results. So from now on use “Kalman Filter”.

2. Prediction Parameters – If client specifications allow prediction of position then this can be enabled. If the computation loses the USBL signal it will then predict the track of the ROV based upon the DVL data only. The maximum prediction age may be determined by the project procedures.

The prediction function can also be used to show a DVL only track. This can be done by creating another computation and setting the “Stop prediction at age” to a high value i.e. 3600 seconds. Let the system build some history before the ROV moves off and then un-tick the HIPAP system from within the computation. Qinsy should now be using only the DVL data for the ROV track.

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2.1.3.3 Kalman Filter and DVL Weighting To adjust the weighting of the DVL within the Kalman filter the standard deviation of the USBL system needs to be altered.

Figure 2.1.3.3 DVL Weighting

The default SD for the USBL is 1. If the USBL data is poor, this SD value can be increased. The Kalman filter will then weight the DVL more strongly in its calculation. The processors offline should test a few files to find the optimum settings for the filter.

2.1.3.4 Examples of DVL Integrated Tracks In the online navigation display the online surveyor needs to display 2 ROV objects and trails. One of the ROV’s will be using raw USBL only and the other will be the DVL Integrated track.

Standard Deviation



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Figure 2.1.3.4a Online Track Comparison – SD 5

In the example shown above the blue ROV and trail is computed using only raw USBL data. The yellow ROV and trail has been computed using a low Kalman filter and a SD setting on the USBL of 5.

Figure 2.1.3.4b Online Track Comparison – SD 25

In the example shown above, the yellow track has more influence from the DVL because the SD setting on USBL was set to 25. The drift away from the blue track is possibly that the C-O for the heading of the DVL is slightly incorrect. But the example does show the effect of changing the SD to weight the Kalman filter in favour of the DVL.



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3 Parascientific Digiquartz Pressure Unit

The digiquartz pressure unit outputs pressure to QINSy. Deepocean instructed QPS to develop software that would decode the pressure output from the unit and convert it to depth using a Simplified Method or the Unesco pressure to depth formulas.

3.1.1 Basic Principles The basic principle of the bathy operation is that to get accurate and repeatable depth readings, we need the following:

An accurate barometric pressure reading at sea-level A calibrated offset figure from the calibration certificate The local gravity (as calculated from the latitude at work site) The mean density of the water column

3.1.2 Barometric Pressure

Ideally a calibrated digital barometer will be interfaced to the QINSy online navigation system. If this is not the case then a atmospheric pressure can be entered manually.

3.1.2.1 Interface of Barometer The barometer should be interfaced as an “Underwater Sensor” on the vessel. (A little confusing)

Note, it is on the Vessel Volantis

Check that Units are correct

If output is mbar then scalefactor needs to be entered



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If no barometer is interfaced, the user will have the option to enter the atmospheric pressure manually. The advantage of an interfaced barometer is that the calculated depth will be correct with the most up to date atmospheric pressure.

3.1.3 Calibrated Digiquartz Unit The Parascientific Digiquartz should only be used if it has a valid calibration certificate. The sensor should ideally be mounted vertically with the pressure sensor at the top. Read the user manual to determine the reference point of the unit. This reference point is where the offsets in relationship to the ROV should be measured.

3.1.3.1 Interface of Digiquartz The digiquartz should be installed as an “Underwater Sensor” and located on the ROV.

Choose Barometer

here



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A generic driver should be written to decode the pressure output from the digiquartz. Care should be made about the units.

When online in QINSy the digiquartz will visible on the height tab of the computation setup.

3.1.4 Local Gravity The local gravity of the location will be computed by QINSy using position from the interfaced GPS units.

Units are entered here.

C-O from Calibration Certificate

Select Digiquartz here



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3.1.5 Mean Density Profile As part of the development of the digiquartz driver QINSy can now calculate a density profile if it is supplied with the correct information from a CTD profile.

The import routine is not perfect yet because the above example is the only input method that will calculate depth and density from the other information. All columns need to be filled in even it is filled in with zeros. If it is not possible to enter a CTD profile and a third party piece of software has calculated a mean density, it can be entered on the height settings tab.

Select / manual or

Active Profile



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3.1.6 Digiquartz Online check

As the digiquartz unit is outputting pressure, it is a good idea to check all the calculations are being performed correctly. With QINSy in online mode, create a Observation Physics display.

Add the observation for the digiquartz pressure and the pseudo observation for digiquartz depth. If the unit is on deck, then the calculated depth should read very close to zero and the pressure should be very similar to that of the barometer. DO-NOT Tare the digiquartz as this is taken care of in the QINSy software. Once the digiquartz is in the water it would be wise to double check everything is working correctly by completing the “digiquartz driver log” in the Operational Online_Form_Pack_ROV.xls.



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4 Seaking SONV3 Bathymetric Unit

The Seaking contains a Parascientific Digiquartz pressure unit. The topside of the Seaking will convert these raw pressure readings to a depth as long as the following basic principles are followed. The Seaking bathy topside is calculating pressure to depth in a similar way to QINSy. The Seaking was used primarily on Deepocean UK projects before the development of the DigiQuartz driver within QINSy.

4.1.1 Basic Principles The basic principle of the bathy operation is that to get accurate and repeatable depth readings, we need the following:

An accurate barometric pressure reading at sea-level A calibrated offset figure from the calibration certificate The local gravity (as calculated from the latitude at work site) The mean density of the water column The output string set to “WINSON RAW”

4.1.1.1 Barometric Pressure A digital barometer for the purpose of supplying an accurate sea-level pressure before every dive must be used. Do not depend on the analogue sensor on the bridge.

4.1.1.2 Calibrated Offset Each Seaking bathy unit comes with 2 calibrated offsets, for a port-up and port-down configuration. It is recommended that we orientate the vertically sensor in a port-up configuration as this is how the sensor is originally calibrated (more later).

4.1.1.3 Local Gravity The local latitude at the work-site is entered in to the top side.

4.1.1.4 Output String

The output string sent to QINSy to be “WINSON RAW” as this will not include any offset figures and will be just the raw depth reading at the level of the sensor. Other output strings such as “WINSON PROC” which does include the bathy and altimeter offsets applied in the top unit (these are used by the ROV crew to give an accurate depth off bottom for the skids on their Tritech display). It will also include the “DQ Offset” (more on this shortly)



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4.1.2 Deepocean Bathymetric Sensor Setup

The bathy unit rarely gets the time to sufficiently warm up and in addition to this, it has frequently been standard practice to “zero” the sensor on deck, using the “DQ offset” facility. There are several issues here:

With the output set to WINSON RAW this “zeroing” will have no effect anyway However,

If the unit is not temperature-stable, the sensor will continue to “creep” after “zeroing” If this “zeroing” is performed with an offset in QINSy, this creep will have an effect If we use the sensor and barometer correctly we should not need zero the bathy.

It is also not common practice to wash the sensor down after a dive. There is a fresh water hose next to the ROV and there is no excuse for this not to form part of the post-dive procedure. I am aware that the ROV crew is reluctant to move the sensor as they are restricted on space and so forth but every effort should be made to construct a bracket to permit a vertical mounting. The difference between the “port-up” and “port-down” offset is over 1m. The difference between the horizontal and either port-up or port-down is unknown. Referring to p.16 of the Tritech Seanet System User Guide: “The digiquartz pressure sensor is a fluid-filled instrument. The weight of the fluid acting on the sensor’s diaphragm varies with the orientation of the sensor and this affects the pressure reading. The unit is calibrated with the pressure port inlet “up”. With an accurate Barometric Pressure applied and the Bathy mounted in the orientation as when it was calibrated, the depth output should be very close to zero when on deck”



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4.1.2.1 Pre-Dive and Post Dive Seaking Procedure

1. Have the Seaking bathy sensor mounted “port-up” 2. Measure and re-measure the vertical offsets from bathy port and altimeter to the CRP

and enter in to QINSY 3. Ensure that the Seaking output is set to “WINSION RAW” 4. Power the Seaking unit up 1-2 hours before diving. Make a note in the log of the time it

was powered on. Don’t wait until you are on site before asking the ROV crew to power up. This may not always be possible but make the best effort not to put the sensor in “cold”

5. Obtain the correct calibrated offset figure from the cal. cert and enter this in to QINSy. If the sensor is mounted any other way other than Vertical PORT up the sensor may still not read zero. Log data over a time period as long as possible to obtain the depth on deck. This can be entered as the variable C-O into Qinsy. This should only be done once prior as part of the mobilization procedure. The following pre-dive checks should then be followed.

6. Obtain an accurate barometric reading from the digital barometer and enter into the Seaking topside computer, making a note in the log book also.

7. Ensure the correct local latitude is set

At this point, the on-deck bathy reading in QINSy should be a few cms either side of zero. If not, either the sensor is not temperature stable or there is a fault with the sensor (possibly clogged). The first course of action is to check to see if the port is clean.

Warning – if the ROV has recently been in the water, it is possible that the sensor will take some time to adjust back to zero –I suggest you plot this over time to get an idea of the recovery time (it is analogous to getting water in your ear after a swim and forms an exponential graph). If the ROV is to make only a brief return to deck, do not be alarmed if the subsequent off-deck bathy reading is not zero. This is why we use the calibrated vertical offset as a benchmark. Historically, surveyors have “chased” the zero value around by putting erroneous zero-offsets in to the unit with obvious consequences

8. Perform a CTD profile and enter the mean density figure in to the Seaking unit. 9. Make a note of the off-deck depth value. If, over a period of time, these values start to

increase, it is an indication that the sensor needs cleaning.



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10. Perform whatever tasks are required of the ROV and return to deck. 11. When on deck, record the time, the on-deck depth value and atmospheric pressure.

Observe the recovery period for future reference.

12. Wash the sensor with fresh water if it is not to be used imminently

4.1.3 Seaking Bathymetric Online Procedure If all the Pre-dive checks have been performed correctly, the unit is reading accurate depths.

4.1.3.1 Atmospheric Pressure Changes in atmospheric pressure throughout the ROV’s dive will affect the readings on the Seaking bathy unit. At present there are 3 options for dealing with atmospheric pressure.

1. Interface the digital barometer directly to the topside of the Seaking unit. If this is possible the sensor of the barometer should be installed outside of the vessel to reduce the affects of pressurised air-conditioned rooms. The interface should also be teed off into Qinsy as well so that there is a recorded file of atmospheric pressure. If this method is successful then the depths obtained from the Seaking will always be correct for atmospheric pressure.

2. Enter the correct atmospheric pressure into the topside of the Seaking unit just before the ROV goes off deck to start the dive. Record the pressure in the online logbook and set up an alert in Qinsy that will turn red if the pressure changes by more than 2mb at which point the new atmospheric pressure should be entered into the Seaking. This will result in 2cm shifts in the depth profile every time a new pressure is entered.

3. Enter the correct atmospheric pressure into the topside of the Seaking unit just before the ROV goes off deck to start the dive and record the pressure in the online logbook. Nothing more is then done with the pressure online and it will be taken care of in processing. The processors will take the pressure file recorded in the Qinsy database and will adjust the tide file by the variations in atmospheric pressure. This method removes responsibility from the online surveyor but adds work to the processing procedure.



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5 Static Noise Test

Before an OOS survey can be undertaken a static noise test of the Seaking needs to be performed. The purpose of the static noise test is to record the influence of surface swell upon the Seaking bathy unit sitting stationary on the seabed. The static noise can be performed at the same time as the TSS440 Background compensation is taking place. The online surveyor should log the bathy data for at least 5 minutes. A file should then be exported in Excel and the standard deviation of the data set should be calculated. If the standard deviation is greater than the procedures state for OOS surveys then the offshore project manager should be informed so that it can be advised that sea conditions are not favorable for an OOS survey.

6 Effects of Speed on Bathymetric Units

The speed at which the ROV travels has an effect on the noise seen in the bathymetric data as can be seen in the graph below.

The right hand side of the graph shows acceptable data, where as on the left the data has more noise, in this case caused by excessive speed. It is therefore important that the online surveyor creates a Time-Series Depth v Time graph in Qinsy online. A suitable time period and vertical scale should be in place, in order that the noise of the Bathy can be monitored online and cross-referenced to other time series graphs. Particular attention should be paid to the quality of this data, if the data is too noisy, then the survey will need to be re-run.



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7 TSS440 Pipetracker

Prior to performing a survey with the TSS440 a few routines must be followed.

On fitting the TSS coils to the vehicle, the system will be checked for excessive noise and if any noted, the coils will be re-positioned on the ROV. Once the coils are fitted it is preferred that boom arms and/or manipulator are not moved following the initial compensation.

Enter the Target Scaling factor. This should be supplied from the client who should have sent a piece of pipeline to TSS to determine the optimum scaling factor.

Perform background compensation; wait at least 20 minutes after the system is immersed into the water. (Please refer to TSS440 manual for complete background compensation procedures.

Select temperature band for seawater compensation. Move the ROV forwards 10m and settle on seabed, check all signal strengths fall to less

than 10 µV. Perform lift off test – raise the ROV slowly 5m off the seabed logging data in the TSS440 and

in Qinsy, the signal strengths should remain less than 10 µV. Do NOT perform a manual seawater compensation (refer to TSS440 manual for details on whether a manual seawater compensation is required), if the signal strengths exceed the 10 µV repeat the compensation and the lift off test again. If the result is the same make a record in the log book and proceed with the rest of the test.

Perform background noise test – survey a fictitious pipeline for 15 minutes with a speed of 1 m/s logging the background noise file.

During the survey, the following criteria should be adhered to.

The centre of the pipeline should be maintained within the frame dimensions and preferably within +/- 40 cms of the centre coil (this figure depends on the tests carried out at TSS. During the survey, the ROV pilot will have the signal strength in the form of a left/right indicator which should be carefully monitored. Any ROV position data outside the coils should be considered cautiously.

The Pipetracker data will be continuously recorded and the vertical top of pipe profile generated in real-time by adding the bathymetric pressure data of the stern mounted system. The relationship between top of sediment and natural seabed will be obtained from the MBES system and further related to MSL by using the bathymetric system. Tidal reduction using predicted tides will be applied.



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The survey speed should be a compromise between slow for adequate scan density and relatively fast to maintain good ROV stability. Normal speed will be between 400-700 m/hrs or as governed by ROV maintaining zero pitch.

7.1 TSS440 – QINSy Setup (Multi-beam Echo sounder driver)

In order to process the TSS440 data easily in QINSy validator the TSS440 needs to be treated as a multibeam echo sounder.

However, the TSS440 is not an echo sounder so on the next page of the database setup there is a couple of tick boxes that need ticking.

QINSy needs to be fooled that the beam data from the TSS440 is already corrected for Pitch and Roll. This is done by ticking the boxes above. If they are not ticked QINSy will pitch and roll correct the beam data which will be incorrect because the TSS440 is a pipetracker measuring magnetic fields which will be closest point of return to the centre coil.

These need to be ticked

The QINSy driver decodes 2 beams. Beam 1 represents the actual pipe line target computed from the VRT. Beam 2 represents the seafloor above or below the pipe. See Qinsy drivers manual for more detailed desciption



Ref.: UK.SUR.WP.003

Rev.: A3


Page 27 of 28

In the diagrams below it shows why Pitch and Roll correction would be wrong. Diagram 1 – ROV with no pitch.

Diagram 2 – ROV with exaggerated pitch for example.

So the above diagram shows the pipeline would be incorrectly positioned if the VRT was pitch corrected. The same principle applies to the roll. So please en-sure that the tick boxes are ticked.

ROV

Pipeline

TSS440

VRT

ROV

Pipeline

VRT with no pitch correction

VRT with pitch correction



Ref.: UK.SUR.WP.003

Rev.: A3


Page 28 of 28

7.2 TSS440 – QINSy Setup (Miscellaneous System)

The previous section describes the TSS440 being treated as an echo sounder. In this mode QINSy throws away all other parts of the data message. For this reason it is good practice to split the TSS440 data cable into 2 comports. On the second comport set up a miscellaneous driver to decode all the information sent from the pipetracker. Even though this data might never be looked at, it is better to have saved it than to never have recorded it.

A generic driver is used to decode the information and a copy of this driver is embedded in this document. !!Embed file once recievied from Advancer!!!

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TSS440 Online OOS Procedures-Rev3

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