`Workman et al.
`
`Ill 11111111111111111111
`
`US005790472A
`[llJ Patent Number:
`[45] Date of Patent:
`
`5,790,472
`Aug. 4, 1998
`
`[54] ADAPTIVE CONTROL OF MARINE SEISMIC
`STREAMERS
`
`[75]
`
`Inventors: Ricky L. Workman; Ronald Edward
`Chambers. both of Houston. Tex.
`
`[73] Assignee: Westem Atlas International, Inc .•
`Houston. Tex.
`
`[21] Appl. No.: 771,849
`
`[22] Filed:
`
`Dec. 20, 1996
`
`6
`
`··-··················································· G01V 1/38
`Int. CI.
`[51]
`£521 u.s. c1. ................................................. 367n9; 367/16
`[58] Field of Search .................................. 367116. 19. 20.
`367/106. 130. 17; 114/253
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`3,931,608
`4,033,278
`4,037,780
`4,187,492
`4,404,664
`4,463,701
`4,729,333
`4,809,005
`4,890,568
`4,912,682
`5,031,159
`
`111976 Cole ...................................... 340f7 PC
`7/1977 Waters .................................... 1441245
`5/1978 Itria et al. ................................... 340n
`211980 Delignieres ............................... 367119
`9/1983 Zachariadis ............................... 367/19
`8/1984 Pickett et al ............................ 114/245
`3/1988 Kirby et al ............................. 1141244
`211989 Counselman ............................ 3421352
`111990 Dolengowski .......................... 1141246
`3/1990 Norton, Jr. et al ....................... 367/19
`7/1991 Rouquette ............................... 367/130
`
`5,353,223 10/1994 Norton et al. .. ........................ 364/421
`5,443,027
`8/1995 Owsley et al ........................... 114/244
`5,532,975
`7/1996 Elholm ...................................... 367/16
`
`OTHER PUBUCATIONS
`
`M. Schoenberger and J. F. Misfud, "Hydrophone Streamer
`Noise", Geophysics. vol. 39. No. 6, pp. 781-793.
`Franklyn K Levin in "Short Note: The Effect of Binning on
`Data from a Feathered Streamer''. Geophysics, vol. 49. No.
`8. pp. 1386-1387.
`Mamdouh R. Gadallah, "Reservoir Seismology". Pennwell.
`1994. pp. 209-237.
`Manin et al .• "Recent Developments in Source and Streamer
`Positioning" First Break. vol. 6. pp. 183-188, Jun. 1981.
`
`Primary Examiner-Ian J. Lobo
`Attome;; Agent, or Firnr-James Randall Allen; Charles R.
`Schweppe
`
`[57]
`
`ABSTRACT
`
`A method for controlling the position and shape of marine
`seismic streamer cables, whereby a plurality of real time
`signals from a marine seismic data acquisition system and a
`plurality of threshold parameters from an input device are
`received. The real time signals are compared to the threshold
`parameters to determine if the streamer cables should be
`repositioned. The streamer cables are repositioned when the
`real time signals exceed the threshold parameters.
`
`10 Claims, 3 Drawing Sheets
`
`01
`
`~
`
`14
`
`15
`
`14
`
`1
`
`ION 1004
`
`
`
`~
`
`s,
`11
`("C
`t:r'
`Cfj
`
`1-'
`
`00
`\C
`\C
`1-'
`'"
`~
`~
`>
`
`14
`
`15
`
`US. Patent
`
`Aug. 4, 1998
`
`Sheet 1 of 3
`
`5,790,472
`
`14
`
`14
`
`14
`
`
`
`14
`
`
`
`
`
`14
`
`15
`
`
`
`14
`
`~ 14
`
`01
`
`l
`
`Fig.
`
`2
`
`
`
`05 Marine seismic data acquisition system
`
`----,
`
`40
`
`/
`
`control
`streamer
`
`~--~--~~rrni~I~2
`
`1.6 II
`I
`I
`I
`I
`I
`I
`I
`I
`I
`!
`
`_ ______ _j
`I
`I
`I
`I
`I
`I
`
`controller
`cable
`streamer
`
`18
`
`system
`recording
`data
`seismic
`
`---
`
`system
`binning ~
`
`...--------
`
`~----
`
`seis~~r·
`
`30
`
`10
`
`system
`
`20
`
`systern
`positioning
`vessel
`
`L __ _
`I
`I
`I
`I
`i
`
`I
`I
`I
`I
`I
`I
`I
`1
`
`~---------------------
`
`Fig. 2
`
`3
`
`
`
`No
`
`wab!~_noise threshold?
`eed the maximum
`
`~s hydorphone noise
`
`/49
`
`hydrophone noise.
`of rnaximum allowable
`noise to the threshold parameter
`Compare real time hydrophone
`
`/48
`
`lit
`Yes
`
`No
`
`being recorded?
`Is seismic data
`
`/'"'" 4 7
`
`. ( Yes
`
`correction.
`
`45
`
`lit
`No
`
`I At risk position
`
`'
`
`correction .
`Calculate position I-/
`
`43
`
`Yes
`
`44
`
`t
`
`. t. 1·
`
`Jl' J~
`restart.
`and
`111 1a 1zel------'
`I
`
`jl'
`
`~41
`
`-
`
`vt2
`
`-
`
`,..
`"'
`
`-~
`
`..--No
`
`···----
`
`to threshold pararneters.
`-Compare real time signals
`...
`
`any threshold parameters?
`Does any signals exceed
`
`~ •
`
`•
`00
`0 •
`
`I
`
`-
`
`-
`
`-
`
`-
`
`-
`
`-· -
`
`------
`
`40 Streamer Control Processor
`
`___. __. .
`
`-----
`
`3
`
`It
`
`I
`I
`I
`I
`I
`I Fig.
`I
`I
`I
`I
`I
`I
`I
`I
`I
`device
`I
`to streamer I
`correction
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I terminal
`I from
`32
`I parameter
`s
`1Threshold
`I
`
`-
`
`""'
`...
`
`16
`
`Jl'
`
`"'
`.... controller.
`
`(~6
`
`-Send
`
`,..
`
`Signals 1 from 18
`
`10
`
`Signals l from 30
`l£08 s
`s·
`
`rom
`
`1 I f
`r-·-
`
`L
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`
`4
`
`
`
`5,790,472
`
`1
`ADAPTIVE CONTROL OF MARINE SEISMIC
`STREAMERS
`
`5
`
`lO
`
`BACKGROUND OF THE INVENITON
`1. Field of the Invention
`The present invention generally relates to an improved
`system for controlling the position and shape of marine
`seismic streamers.
`2. Description of the Related Art
`During a typical marine seismic survey a seismic vessel
`traverses programmed tracks towing arrays of seismic
`sources and seismic streamer cables. A seismic streamer
`cable normally contains a plurality of hydrophones which
`convert seismic pressure waves, initiated by the sources and 15
`reflected from the subsurface geologic formations. into
`electrical signals which are recorded on a marine seismic
`data acquisition system located on the vessel. Due to the
`increasing use of marine 3-D seismic data, multi-cable
`marine surveys are now commonplace. During a typical 20
`marine 3-D seismic survey. a vessel may tow as many as ten
`streamer cables, each cable ranging in length between three
`to eight kilometers. As reported by Gadallah in ''Reservoir
`Seismology" 1994. pp. 209-237. the goal of a normal
`marine 3-D seismic survey is to use these arrays of seismic 25
`sources and streamer cables to record a highly sampled grid
`of "bins" of subsurface seismic coverage.
`A natural consequence of towing such streamer cable
`configurations in a marine environment is that currents.
`wind. and wave action will deflect the streamer cables from 30
`their intended paths. Streamer cable drift is a continuing
`problem for marine seismic surveys. See, for example. U.S.
`Pat. No. 5.532,975. The ability to control the position and
`shape of the streamer cables is desirable for preventing the
`entanglement of the streamer cables and for avoiding colli- 35
`sions with offshore hazards such as marine drilling rigs and
`platforms. It is also desirable to have the ability to control
`the position and shape of the streamer cables during marine
`3-D seismic surveys because the 3-D seismic binning pro(cid:173)
`cess acquires subsurface seismic coverage by combining 40
`seismic data from different lines. The need for this ability is
`taught by Franklyn K. Levin in "Short Note: The effect of
`binning on data from a feathered streamer." Geophysics.
`Vol. 49. No.8. pp. 1386-1387.
`Streamer positioning devices are well known in the art. 45
`Apparatus. such as those disclosed in U.S. Pat. Nos. 5.532,
`975, 4,729,333, and 4.463.701. have been devised for
`attachment to the front end of streamer cables for the
`purpose of maintaining them at a lateral offset to the
`pathway of the towing vessel. Steerable tail buoys. as so
`described in U.S. Pat. No. 4.890.568, have also been
`designed for controlling the position of the tail end of towed
`seismic streamer cables. The prior art also discloses streamer
`positioning devices that may be attached externally to the
`streamer cables. For example. devices to control the lateral 55
`positioning of streamer cables by using camber-adjustable
`hydrofoils or angled wings are disclosed in U.S. Pat. Nos.
`4,033,278 and 5.443.027. U.S. Pat No. 3,931,608 describes
`an apparatus. typically known as a "bird", to control the
`vertical positioning of streamer cables with diving planes 60
`and a preset depth control means.
`The use of streamer positioning devices comes at the price
`of introducing increased noise onto the seismic streamer and
`hence into the hydrophones. The areas of greatest noise are
`from those hydrophones which are adjacent to externally 65
`attached streamer positioning devices, such as depth con(cid:173)
`trolling birds. This problem has been descnbed by Schoe-
`
`2
`nberger and Misfud. "Hydrophone Streamer Noise"
`Geophysics, Vol. 39. No.6. pp. 782-784. It is well known
`in the art that noise limits the resolution of a seismic survey.
`Consequently. a maximum allowable hydrophone noise
`level is typically established for each marine seismic sur(cid:173)
`veying project. When this noise level is exceeded. seismic
`acquisition is usually suspended. resulting in lost time and
`additional cost. Data acquired under such conditions may
`need to be reshot.
`Location sensing devices and methods for determining the
`positions of the seismic sources and seismic streamer cables
`are also well known in the art. For example, both a Global
`Positioning System. as described in U.S. Pat. No. 4.809.005.
`and a network of acoustic elements. as described in U.S. Pat.
`No. 4.912.682 may be deployed on the vessel. streamer
`cables. and tail buoy. These devices and methods may then
`be used to determine the real time position of the seismic
`sources and seismic streamer cables by computing a network
`solution to a Kalman filter. as disclosed by U.S. Pat. No.
`5.353.223.
`As is known to those familiar with the art of marine
`seismic surveying, during a typical survey a human operator
`monitors the survey's operational conditions. such as the
`extent of the subsurface seismic coverage. the adequacy of
`the separations between streamer cables, and the proximity
`of the streamer cables to obstructive hazards. When these
`conditions indicate the need to reposition the streamer
`cables, the operator may manually issue commands to the
`various individual streamer positioning devices in order to
`adjust the position and shape of the streamer cable. or order
`the helmsman to redirect the vessel, or suspend data acqui(cid:173)
`sition.
`While the prior art discloses a series of discrete devices
`for locating and controlling the positions of streamer cables.
`it does not teach any method or system wherein these
`individual devices are unified into a single system for
`controlling the position and shape of marine seismic
`streamer cables. Also. the prior art fails to disclose any
`method or system wherein the real time hydrophone noise
`on the streamer cables operates as a constraint on the control
`of the position and shape of marine seismic streamer cables.
`The present invention overcomes the limitations of the
`prior art by providing an improved system for controlling
`the position and shape of marine seismic streamer cables.
`SUMMARY OF THE INVENITON
`The present invention is an improved system for control(cid:173)
`ling the position and shape of marine seismic streamer
`cables. First, a plurality of real time signals from a marine
`seismic data acquisition system and a plurality of threshold
`parameters from an input device are received. Second. the
`real time signals are compared to the threshold parameters to
`determine if the streamer cables should be repositioned.
`Finally. the streamer cables are repositioned when the real
`time signals exceed the threshold parameters.
`BRIEF DESCRIPITON OF THE DRAWINGS
`FIG. 1 shows a generalized schematic of a marine seismic
`survey system.
`FIG. 2 shows a block diagram of a marine seismic data
`acquisition system in the improved system for controlling
`the position and shape of marine seismic streamer cables.
`FIG. 3 shows a :flow chart illustrating certain steps of a
`streamer control processor
`DESCRIPITON OF THE PREFERRED
`EMBODIMENT
`FIG. 1 illustrates a generalized schematic of a type of
`marine seismic survey system 01. This system 01 has a
`
`5
`
`
`
`5,790,472
`
`3
`vesselll. a plurality of seismic sources 12 and a plurality of
`streamer cables 13 under tow behind the vessel 11, and a
`marine seismic data acquisition system OS, which is onboard
`the vesselll and connected to the seismic sources 12 and the
`streamer cables 13. The seismic sources 12 generate seismic
`pressure waves. Hydrophones (not shown) in the streamer
`cable 13 receive pressure wave signals and send them to the
`marine seismic data acquisition system OS. The marine
`seismic data acquisition system IS records pressure wave
`signals received from the streamer cable 13. controls the
`seismic sources 12 and the streamer cables 13. and monitors
`the seismic sources 12. the streamer cables 13. and the
`acquisition of subsurface seismic coverage.
`As known to those skilled in the art. streamer positioning
`devices 14. for example birds and tail buoys. may be
`attached to the exterior of the streamer cables 13 for adjust(cid:173)
`ing the vertical and lateral positions of the streamer cables
`13. The streamer cables 13 include electrical or optical
`cables for connecting the streamer positioning devices 14 to
`individual control and logging systems. for each type of
`device, in the marine seismic data acquisition system IS.
`Typically. location sensing devices 1S may be used for
`observing the position of the streamer cables 13 and seismic
`sources 12. The marine seismic data acquisition system OS
`uses these position observations to determine the position of
`the streamer cables 13 and seismic sources 12. As known to
`those skilled in the art. the location sensing devices 15 are
`connected to the marine seismic data acquisition system OS
`by electrical or optical cables within the streamer cables 13
`or by radio transmitter means.
`Referring now to HG. 2. the interrelationship of the
`devices in the marine seismic data acquisition system OS of
`the preferred embodiment of the present invention is shown.
`As known to those skilled in the art. components of the
`marine seismic data acquisition system OS. on the vesselll.
`may include a vessel positioning system 2t for determining
`the position of the vesselll by satellite navigation, a seismic
`data recording system 18 for recording signals received from
`hydrophones in the streamer cables 13. a seismic binning
`system 3t for determining the subsurface seismic coverage
`during the seismic survey. a network solution system 11 for
`determining the position of the streamer cables 13 and
`seismic sources 12. and a streamer cable controller 16 for
`controlling the streamer positioning devices 14. (For clarity.
`only one streamer cable 13 and one seismic source 12 are
`shown in HG. 2).
`Typically, the network solution system 10 implements a
`Kalman filter solution on the signals it receives from the
`vessel positioning system 2t and location sensing devices
`1S. The network solution system 10 outputs real time
`streamer cable shapes. streamer cable positions. and
`streamer cable separations. The seismic binning system 30
`receives these real time signals from the network solution
`system 10, and utilizes them to determine and output real
`time subsurface seismic coverage. The seismic data record(cid:173)
`ing system 18 is connected to the streamer cables 13 and
`may output real time signals indicating whether or not the
`streamer cables 13 are recording seismic data and real time
`signals of hydrophone noise on the streamer cable 13.
`In the present embodiment of the invention. the marine
`seismic data acquisition system OS also includes a streamer
`control processor 4t for deciding when the streamer cables
`13 should be repositioned and for calculating a position
`correction to reposition the streamer cables 13. Also in the
`present embodiment of the invention. threshold parameters
`are established for determining when the streamer cables
`should be repositioned. Threshold parameters may include a
`plurality of values for: minimum allowable separations
`between streamer cables 13. minimum allowable subsurface
`
`4
`seismic coverage. maximum allowable hydrophone noise
`levels. and minimum allowable separations between any
`streamer cable 13 and any obstructive hazard. A terminal 32
`for entering threshold parameters is connected to the
`5 streamer control processor 41. Threshold parameters may be
`entered into the streamer control processor 40 before or
`contemporaneously with the acquisition of a marine seismic
`survey.
`The streamer control processor 40 is connected to the
`network solution system 10. the seismic binning system 31.
`10 the streamer positioning control devices 14. and the seismic
`data recording system 18 and receives the real time signal
`outputs of these systems. The streamer control processor 4t
`evaluates these real time signals and the threshold param(cid:173)
`eters from the terminal 32 to determine when the streamer
`15 cables 13 need to be repositioned and to calculate the
`position correction required to keep the streamer cables 13
`within the threshold parameters. The streamer control pro(cid:173)
`cessor 4t is connected to the streamer device controller 16.
`When the streamer cables 13 need to be repositioned. the
`position correction is used by the streamer device controller
`20 16 to adjust the streamer positioning devices 14 and repo(cid:173)
`sition the streamer cables 13.
`Referring now to HG. 3 and FIG. 2. the process steps of
`the streamer control processor 4t will now be described. At
`step 41. the streamer control processor 4t determines if the
`25 streamer cables 13 need to be repositioned by comparing the
`real time signals received from the network solution system
`lt. the seismic binning system 30, and the seismic data
`recording system 18 with the threshold parameters received
`from the terminal 32. At step 42. it is determined if any of
`30 the real time signals exceed any threshold parameter
`received from the terminal 32. At step 43. if any such
`threshold parameter is exceeded, a position correction is
`calculated that will reposition the streamer cables 13 back to
`within the threshold parameters. If no signal exceeds any
`threshold parameter. the streamer control processor 4t is
`35 initialized and restarted at step 44.
`Since streamer positioning devices 14 create noise on
`hydrophones in the streamer cable 13. the present invention
`controls the use of the position correction by determining
`when the hydrophone noise level should prevent the repo-
`40 sitioning of the streamer cable 13. Occasionally. towed
`streamer cables encounter "at risk" situations. For example,
`they face the possibility of becoming entangled with each
`other or of colliding with an obstructive hazard. When the
`streamer cables 13 are being repositioned to avoid such at
`45 risk situations the position correction should be imple(cid:173)
`mented without considering the hydrophone noise levels.
`At step 45. it is determined if the position correction is due
`to an at risk situation. If an at risk situation exists. at step 46
`the streamer position correction is sent to the streamer
`50 device controller Ui for adjusting the streamer positioning
`devices 14 to reposition the streamer cables 13. If an at risk
`situation does not exist, at step 47 it is determined if the
`streamer cables 13 are being used to record seismic data by
`evaluating the real time signals and recorder status from the
`seismic data recording system 18. If the streamers cables 13
`55 are not being used to record seismic data. at step 46 the
`streamer position correction is sent to the streamer device
`controller 16 for adjusting the streamer positioning devices
`14 to reposition the streamer cables 13.
`,It is well known in the art of marine seismic data
`60 acquisition that hydrophone noise limits the resolution of
`marine seismic surveys. The preferred embodiment of the
`present invention constrains the repositioning of the
`streamer cables 13 by evaluating the hydrophone noise level
`of the streamer cables 13 when the streamer cables 13 are
`65 being used to record seismic data.
`It is also well known in the art of marine seismic data
`acquisition that maximum allowable noise level thresholds
`
`6
`
`
`
`5,790,472
`
`35
`
`40
`
`5
`may be established for marine seismic surveys and, when
`these thresholds are exceeded. data acquisition may be
`suspended or the affected portions of the surveys may have
`to be reacquired. Maximum allowable noise thresholds may
`be chosen in several ways. A single noise threshold, which 5
`is applied across the entire frequency spectrum of the
`seismic survey, may be chosen as the maximum allowable
`noise threshold. A weighted noise threshold. which varies
`and is applied as a function of the frequency spectrum of the
`seismic survey. may be chosen as the maximum allowable
`noise threshold. Also. measurements of background noise 10
`may be made on hydrophones in the streamer cables 13 and
`used to determine either the single noise or weighted noise
`thresholds.
`At step 48. the control on the repositioning of the streamer
`cables 13. due to the level of hydrophone noise. is deter- 15
`mined by comparing the real time signals of hydrophone
`noise from the seismic data recording system 18 with the
`threshold parameters of maximum allowable hydrophone
`noise. At step 49. it is determined if the real time signals of
`hydrophone noise from the seismic data recording system 18
`exceed any threshold parameter of maximum allowable
`noise. If the real time hydrophone noise exceeds any thresh(cid:173)
`old parameter of maximum allowable noise. at step 44 the
`streamer control processor 40 is initialized and restarted. If
`the real time hydrophone noise does not exceed any thresh(cid:173)
`old parameter of maximum allowable hydrophone noise. at
`step 46 the streamer position correction is sent to the
`streamer device controller 16 for adjusting the streamer
`positioning devices 14 to reposition the streamer cables 13.
`After the position correction is sent to the streamer device
`controller 16 at step 46. the streamer control processor 40 is
`initialized and restarted at step 44.
`What is claimed is:
`1: A s~ste~ for controlling the position and shape of
`manne selSlmc streamer cables. comprising the steps of:
`receiving a plurality of real time signals. including hydro-
`phone noise, from a marine seismic data acquisition
`system and a plurality of threshold parameters. includ(cid:173)
`ing maximum allowable hydrophone noise. from an
`input device;
`comparing the real time signals to the threshold param-
`eters to determine if the streamer cables should be
`repositioned; and
`repositioning the streamer cables when the real time
`hydrophone noise signal is within the maximum allow(cid:173)
`able hydrophone noise threshold and when the remain- 45
`ing real time signals exceed the threshold parameters.
`2. The system of claim 1. wherein the marine seismic data
`acquisition system further comprises:
`a network solution system;
`a seismic binning system; and
`a seismic data recording system.
`3. The system of claim 2, wherein the repositioning step
`further comprises the steps of:
`calculating a position correction that will keep the ss
`streamer cables within the threshold parameters; and
`sending the position correction to a streamer device
`controller for adjusting a plurality of streamer position(cid:173)
`ing devices.
`4. The system of claim 3, wherein the receiving step 60
`further comprises the steps of:
`receiving real time signals including streamer cable
`positions, streamer cable shapes. streamer cable
`separations, obstructive hazard positions. and subsur(cid:173)
`face seismic coverage; and
`receiving threshold parameters including minimum
`allowable separations between streamer cables, mini-
`
`6
`mum allowable separations between any streamer cable
`and an obstructive hazard. and minimum allowable
`subsurface seismic coverage;
`and the sending step further comprises the steps of:
`determining if the streamer cables are in an at risk
`situation; and
`sending the position correction to the streamer device
`controller when the streamer cables are at risk.
`S. The system of claim 4, wherein the receiving step
`further comprises the step of:
`receiving real time signals including recorded seismic
`data; and the sending step further comprises the steps
`of:
`determining if the streamer cables are in use for recording
`seismic data; and
`sending the position correction to the streamer device
`controller when the streamer cables are not in use for
`recording seismic data.
`6. The system of claim 1, wherein the threshold parameter
`20 of maximum allowable hydrophone noise is a single noise
`threshold which is applied across the entire frequency spec(cid:173)
`trum of the seismic survey.
`7. The system of claim 6, wherein the single noise
`threshold is determined from measurements of background
`25 noise made on the streamer cable.
`8. The system of claim 1. wherein the threshold parameter
`of maximum allowable hydrophone noise is a weighted
`noise threshold which varies and is applied as a function of
`the frequency spectrum of the seismic survey.
`9. The system of claim 8, wherein the weighted noise
`30 threshold is determined from measurements of background
`noise made on the streamer cable.
`10. A system for controlling the position and shape of
`marine seismic streamer cables, comprising the steps of:
`receiving a plurality of real time signals, including
`streamer cable positions. streamer cable shapes,
`streamer cable separations, obstructive hazard
`positions, subsurface seismic coverage. recorded seis(cid:173)
`mic data and hydrophone noise. from a marine seismic
`data acquisition system;
`receiving a plurality of threshold parameters. including
`minimum allowable separations between streamer
`cables. minimum allowable separations between any
`streamer cable and an obstructive hazard. minimum
`allowable subsurface seismic coverage and maximum
`allowable hydrophone noise, from an input device;
`calculating a position correction that will keep the
`streamer cables within the threshold parameters;
`determining if the streamer cables are in an at risk
`situation;
`sending the position correction to a streamer device
`~ontroll~ for adjusting a plurality of streamer position(cid:173)
`Ing deVIces when the streamer cables are in an at risk
`situation;
`determining if the streamer cables are in use for recording
`seismic data;
`sending the position correction to the streamer device
`controller when the streamer cables are not in use for
`recording seismic data;
`determining if the real time signals of hydrophone noise
`are within the threshold parameters of maximum allow(cid:173)
`able hydrophone noise; and
`sending the position correction to the streamer device
`controller when the real time hydrophone noise is
`within the maximum allowable hydrophone noise
`threshold.
`
`50
`
`65
`
`* * * * *
`
`7
`
`