Ex. PGS 1010
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`EX. PGS 1010
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`

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`United States Patent [191
`Neeley
`
`[11]
`[45]
`
`4,231,111
`Oct. 28, 1980
`
`[54] MARINE CABLE LOCATION SYSTEM
`[75] Inventor: Walter P. Neeley, Irving, Tex.
`[73] Assignee: Mobil Oil Corporation, New York,
`N‘Y_
`
`4,086,632
`4/1978
`Lions ........................... .. 343/112 PT
`Primary Examiner-Stephen C. Buczinski
`Attorney’ Agent’ or ?rm-“C A‘ Huggett; w'nlam J‘
`Scherback
`
`[21] Appl. No.: 885,916
`[22] Filed:
`Man 13, 1978
`
`1
`[51] Int. Cl.~ ............................................. .. G01‘, 1/38
`[52] {15' Cl- """""""""""
`11096;‘ gig/215336
`
`[58] Field M Search """"""""" " 340/3 T’ 7 R’ 7 PC’
`' 340/155 DS; 114/244, 253; 367/19, 106, 130;
`
`V
`
`343/5 EM
`
`[56]
`
`,
`
`,
`
`References Cited
`Us PATENT DOCUMENTS
`3 840 845 “W974 B
`3,953,827
`4/1976 Moal et al.
`
`rown .............................. ..
`
`340/7 R
`..... .. 340/7 R
`
`ABSTRACT
`[57]
`A marine cable location system includes a plurality of
`magnetic compasses located at known spaced intervals
`along a cabk being towed by a marine vesseL These
`compass readings are recorded along with an onboard
`magnetic compass reading, an onboard gyrocompass
`reading, and satellite navigational information. From
`,
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`3
`these recordings, the X-Y coordinates of cable com
`.
`.
`.
`passes with respect to vessel heading are determined.
`These X-Y coordinates are recorded along with the
`vessel’s position and heading on magnetic tape and a
`cathode-ray tube so as to provide a visual display of the
`cable posmo“ “"th respect to the vessel‘
`
`-
`
`-
`
`-
`
`3,981,008
`4,068,208
`
`343/5 EM
`9/1976 Mann ............... ..
`1/1978
`Rice, Jr. et a]. ................... .. 340/7 R
`
`6 Claims, 5 Drawing Figures
`
`PA .a BCU ,_
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`TAPE
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`RADAR
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`(22
`R E C O R D E R /
`PRINTER
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`KEY BOARD
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`Ex. PGS 1010
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`U.S. Patent
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`Oct. 23, 1980
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`Ex. PGS 1010
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`

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`US. Patent 0a. 28, 1980
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`Sheet 2 of2
`C4
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`4,231,111
`F I G. 4
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`c
`v
`/ / °
`\ VESSEL HEADING
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`91% = OBSTACLE LOCATION
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`Ex. PGS 1010
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`1
`
`MARINE CABLE LOCATION SYSTEM
`
`BACKGROUND OF THE INVENTION
`This invention relates to seismic exploration and
`more particularly to marine exploration. In marine ex
`ploration, seismic energy is generated in the water and
`re?ections of such energy from subsurface interfaces
`are detected by a linear string of detectors or hydro-
`phones. The seismic energy sources and the detectors
`are towed through the water by means of cables extend
`ing from a marine vessel. Signals received by the detec
`tors are transferred to the vessel through the cable wir
`ing. In many instances, groups of detectors are com
`bined to form arrays within the cable, and the signals
`received by each such array are combined and trans
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`0
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`5
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`ferred'toethe vessel.
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`7' ~ ~ 7
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`7
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`4,231,111
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`directional turn. Under certain conditions the vessel
`could even turn sharply enough to cross the cable itself
`as it extends one or more miles behind the vessel.
`It is therefore a speci?c aspect of the present inven
`tion to provide a system for visually displaying the
`position of a towed cable for use by the towing vessel’s
`operator. A plurality of sensors are located at select
`points along the towed cable to provide signals repre
`sentative of the heading of tangents to the cable at such
`select points. A sensor located onboard the vessel pro
`vides a signal representative of the heading of the vessel
`itself. A navigational system onboard the vessel pro
`vides signals identifying the X-Y coordinate of the ves
`sel. The heading signals from the cable sensors and the
`vessel sensor along with the vessel’s X-Y coordinate
`signal from the navigational system are used to deter
`mine the X-Y coordinates for the cablesensors. A visual
`display having a matrix of display squares records the
`X-Y coordinates of the vessel and the cable sensors.
`In one aspect of the invention the vessel sensor and
`the cable sensors are magnetic compasses producing
`signals representing headings with respect to a direction
`of magnetic north. In this aspect, there is also included
`a gyrocompass onboard the vessel for producing a sig
`nal representative of the true north heading of the ves
`sel. The magnetic variations of the vessel compass and
`the cable compasses from true north of the vessel’s
`heading are determined in identifying the X-Y coordi
`nates of the select points along the cable. These X-Y
`coordinates are displayed in a plus X direction off the
`stern of the vessel and a plus Y direction off the star
`board of the vessel.
`In a further aspect, the X-Y coordinates of obstacles
`in the path of the cable as it is being towed are identi
`?ed. These X-Y coordinates are entered into the matrix
`of squares of the visual display along with the X-Y
`coordinates of the vessel and of the select points along
`the towed cable as illustrated in FIG. 3.
`
`One method for determining the instantaneous posi
`tion of each detector or array of detectors along the
`cable as the cable is towed through the water is dis
`closed in US. Pat. No. 3,953,827 to Le Moal et al. A
`plurality of detectors or hydrophones are distributed
`along a towed cable. The position of each detector is
`determined by the interpolation of values of the angle of
`the tangents to the cable with a ?xed and known direc
`tion, such as magnetic north, at a plurality of measuring
`points. At each measuring point along the cable there is
`located preferably a magnetic compass. There is also
`provided means for coding and transmitting the mea
`sured values by means of electronic pulses to a central
`station. Such means includes a multiplex device. The
`position of each measuring point is determined by as
`similating that part of the towed cable located between
`compasses to an arc of a circle, the length of which is
`known from the constructionv of the cable, while the
`angular value of the arc is determined from the differ
`ences between the angles measured by the compasses
`between the tangent to the cable and the ?xed and
`known direction. The positions of the detectors along
`the cable are then determined by interpolation between
`the positions of the compasses along the cable.
`SUMMARY OF THE INVENTION
`In accordance with the present invention there is
`provided a system for determining the position in X-Y
`45
`coordinate a plurality of points along a cable towed by
`a marine vessel and for visually displaying such points
`for use by the vessel’s operator in steering the vessel
`past other vessels or obstacles.
`In the development of marine exploration, the seismic
`detector cables have become quite long, extending for
`one mile, two miles, or even farther behind the marine
`vessel. Such lengths can cause problems in accurately
`determining the position and con?guration of the cable
`as it is towed through the water since it is unlikely that
`cables of such lengths will extend in a straight line be
`hind the towing vessel or even be con?gured in the
`shape of a single arc of curvature. Rather, the cable may
`have one or more inflection points in its curvature and
`may extend laterally to one or even both sides of the
`towing vessel simultaneously as illustrated in FIG. 1.
`One of the primary concerns in towing such a long
`and curved cable is in the steering of the towing vessel
`past other marine vessels or obstacles such as drilling
`towers, etc., in such a way that the projected path of the
`cable does not intersect such other vessels or obstacles.
`This is true not only when the vessel passes such obsta
`cle in a straight line but also when the vessel is in a
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`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 illustrates a seismic exploration system em
`ploying a marine vessel and towed seismic cable.
`FIG. 2 illustrates seismic recording equipment em
`ployed with the marine exploration system of FIG. 1.
`FIG. 3 illustrates a visual display of cable-positioning
`data determined by the recording equipment of FIG. 2.
`FIG. 4 illustrates the geometric con?guration utilized
`in determining cable compass X-Y coordinates.
`FIG. 5 represents a truth table for locating the bear
`ing of the farthest compass from the vessel.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`In seismic marine exploration, the marine vessel 10 of
`FIG. 1 tows a seismic detector cable 11 along a line of
`exploration. Such a cable 11 conventionally employs a
`plurality of detectors, or hydrophones, (not shown)
`spaced along its length for receiving seismic re?ections
`from the subsurface layer below the ocean floor. The
`cable also employs a plurality of magnetic heading sen
`sors 12 equally spaced along its length, ?ve such sensors
`being illustrated in FIG. 1. Each sensor provides a sig
`nal representing the magnetic heading or direction of
`the tangent to that particular point of the cable. By
`knowing the heading of the tangents to the cable at such
`plurality of points along the cable and the distances
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`Ex. PGS 1010
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`4,231,111
`3
`between each of such points, the location of the cable
`ters of interrogator 13 to the external header unit of the
`along its entire length can be estimated.
`?eld recorder 17.
`In the preferred embodiment, each sensor 12 includes
`g In the ?eld recorder 17, the magnetic differences
`a magnetic compass 12a and a binary control unit 12b. A
`between the magnetic compass readings and the gyro
`Model 319 Magnetic Sensor supplied by Digicourse,
`compass reading are determined as indications of the
`Inc., is utilized for each magnetic compass 12a, and a
`magnetic variations of the compass readings from true
`Model 350 Binary Control Unit of Digicourse, Inc., is
`north of the vessel's heading. The compass readings are
`utilized for each binary control unit 12b. The readings
`then read out of the ?eld recorder 17 and into the cable
`of the compasses are multiplexed by the associated bi
`location computer 20 approximately one second before
`nary control units onto a single pair of wires running the
`each ?ring of the seismic acoustic source and the re
`length of the cable to the onboard cable location com
`cording of the resulting seismic re?ection data. Approx
`puting system as illustrated in FIG. 2. Each binary con
`imately 12 seconds are utilized between each such
`trol unit is addressed with its appropriate code number
`source ?ring.
`by the interrogator 13. A Model 290 Data Acquisition
`Following transfer of the corrected compass head
`Unit of Digicourse, Inc., is utilized for such interroga
`ings and the navigation information from the ?eld re
`tor. A start pulse from the cycle timer l4 initiates the
`corder 17, the computer 20 determines the X and Y
`multiplexing of the magnetic compass headings torinfor
`coordinates. of each-.compass, with plus X direction.
`mation registers in the interrogator 13. Also applied to
`being headed off the stern of the ship and plus Y being
`an information register in the interrogator 13 is the
`headed off the starboard of the ship. Also, the bearing
`heading from an onboard magnetic compass 15, such as
`and range of each compass with respect to the ship are
`the Model 101 Magnetic Sensor of Digicourse, Inc. The
`determined. Such determinations are based upon the
`compass heading in any one of the six information regis
`theory that when the tangent of a plurality of points
`ters can be visually displayed on the sensor display 16,
`along the cable (i.e., as indicated by the compass read
`such as a Model 102 Sensor Display of Digicourse, Inc.
`ings) is known and the distances between such points
`The information registers of the interrogator 13 trans
`along the cable are known, then the lengths and direc
`fer the compass headings to an external header unit in
`tions of the chords between such points can be deter
`the ?eld recorder 17. Such ?eld recorder is preferably
`mined, assuming the cable between such points is an arc
`the DFS IV digital ?eld recorder of Texas Instruments
`of a circle. These chords can then be stacked as a pre»
`Incorporated. Also applied to such external header unit
`diction of the cable’s position with respect to the ves
`is the true north reading from an onboard gyrocompass
`sel’s heading as the cable is towed through the water.
`18 and a satellite-positioning reading of latitude and
`Such stacking will also yield a single vector indicating
`longitude from the onboard navigational system 19. The
`the distance of the farthest cable compass from the
`?eld recorder 17 therefore contains all the information
`vessel and the bearing of such compass with respect to
`required by the cable location computer 20 to compute
`the vessel's bearing. Referring more particularly to
`cable position relative to the vessel’s gyroheading. Pref
`FIG. 4, there is illustrated an example con?guration for
`erably, the computer 20 is the Model 980B of Texas
`a towed cable with respect to vessel heading wherein:
`Instruments Incorporated. This computer converts the
`c0=vessel heading with respect to magnetic north,
`compass data into X and Y coordinates for recording on
`c,-=cable headings with respect to magnetic north at
`magnetic tape unit 24, plus X direction being headed off
`the select points of the cable compasses (i.e., c1—c5),
`the stern from the ship and plus Y being starboard from
`40
`,~=chord subtending the arc of curvature of the
`the ship. A simple plot of the ship coordinates and the
`cable between adjacent compasses (i.e., dO-d4),
`cable compasses appears on the cathode~ray tube dis?
`a,-.= angle between the chord d; and the tangent line
`play 21. The computer also provides the bearing and
`for the cable heading 0;,
`range of each compass with respect to the ship. A zero
`b,-= angle between a line pointing in the direction of
`degree (0°) reference is used for the gyroheading of the
`the vessel's heading and the chord d,~, and
`‘ship. Therefore, compass bearings will generally be
`s,-=cable arc length between adjacent compasses.
`around 180". Such bearing and range information are
`Each chord d,- de?ned in the above manner becomes a
`recorded on the recorder 22, preferably a Silent 730
`directed line segment with vector components X; and
`KSR Keyboard Recorder/Printer of Texas Instruments
`Y,-. Computation of the distance R and bearing 0 from
`Incorporated.
`the vessel to the last cable compass is as follows:
`Having generally described the invention in conjunc
`tion with the block schematic of FIG. 2, a more detailed
`description of the operation of the various units of F IG.
`2 will now be described in conjunction with the loca
`tion of the cable 11 during a towing operation.
`During seismic exploration operations, each seismic
`recording cycle is initiated at time zero by a ground
`signal of at least 40 milliseconds but not greater than 100
`milliseconds from the cycle timer 14. If, however, seis
`mic exploration operations are not being carried out, ‘
`the ground signal can be supplied to the interrogator 13.
`from the cable location computer 20. This ground signal
`is utilized by the interrogator 13 to successively address
`each binary control unit 12b for 100 milliseconds. It will
`therefore require 500 milliseconds to read the ?ve cable
`compasses 12a. The onboard magnetic compass is ready
`every 25 milliseconds. It requires 60 milliseconds to
`output the compass readings from the information regis
`
`Examination of the signs ZXi and EY; gives the bearing
`0 with respect to vessel heading as shown in the truth
`table of FIG. 5.
`A typical plot of such cable location with respect to
`the ship for the ?ve~compass cable of the preferred
`embodiment is illustrated in FIG. 3. Such plot is based
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`Ex. PGS 1010
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`4,231,111
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`on a matrix of display squares wherein the entire square
`in which a determined X-Y coordinate falls is bright
`ened on the face of the cathode-ray tube display 21.
`This ?ve-point plot of X-Y coordinates is updated prior
`to each seismic ?ring cycle or approximately every 12
`seconds. Should the vessel change its direction and
`position as indicated by the arrow 25 in FIG. 3, each
`compass position is changed to a new X-Y coordinate
`on the display matrix as indicated by the dashed lines.
`In addition to the visual display of the location of the
`marine vessel and its towed cable, various obstacles that
`lie in the path of the vessel and its cable, such as other
`vessels, drilling towers, etc., may also be displayed with
`their X-Y coordinates. Should the vessel’s radar 23
`identify a possible obstacle, the vessel’s operator may
`enter the obstacle’s X-Y coordinate into the display
`matrix by means ofthe input keyboard of the recorder/
`printer. The display square in which the obstacle’s X-Y
`coordinate falls is brightened on the face of the cathode
`ray tube display 21. For example, the square marked
`with an asterisk, *, in FIG. 3 indicates the position of an
`obstacle lying in a collision path with the cable.
`Various modi?cations may be made to the foregoing
`described embodiment of the present invention without
`departing from the scope and spirit of the present inven
`tion as set forth in the appended claims. For example, in
`lieu of the use of magnetic compasses for the cable
`sensors 12a, there may be employed encoding gyros,
`strain gauges, or even flow sensors connected in bridge
`circuits to detect such things as pressure or temperature
`unbalance across the cable. Also, navigational antennas
`may be located on cable support buoys for sending
`cable heading signals to the vessel. Further, various
`types of recording and display equipment may be em
`ployed on the vessel for indicating cable location.
`I claim:
`1. A system for visually displaying the position of a
`cable towed by a marine vessel, comprising:
`(a) means for providing navigational information
`signals indentifying the X-Y coordinate of said
`marine vessel,
`(b) a sensor located on said marine vessel for provid
`ing a signal representative of the heading of said
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`6
`marine vessel as it tows said cable through the
`water,
`(c) a plurality of sensors located at select points along
`said cable for providing signals representative of
`the heading of tangents to the cable at said select
`points,
`(d) means responsive to the signals from said cable
`sensors, from said marine vessel sensor, and from
`said navigational information means for determin
`ing the X-Y coordinate of each of said plurality of
`cable sensors,
`(e) a visual display having a matrix of display squares,
`(f) means for entering the X-Y position of said marine
`vessel along with the X-Y position of said plurality
`of selected cable points into the matrix of said vi
`sual display, whereby squares of the display matrix
`identi?ed with said entered X-Y positions are visu- .
`ally distinguishable from the remaining squares to
`display a locus of points de?ning the con?guration
`of the towed cable,
`(g) means for identifying the X-Y coordinates of ob
`stacles in the path of said cable as it is being towed
`by said marine vessel, and (h) means for entering
`the X-Y coordinates of said obstacles into the ma
`trix of said visual display to visually display a mark
`representing the position of the obstacle relative to
`the cable.
`2. The system of claim 1 wherein said cable sensors
`and said marine vessel sensor are magnetic compasses.
`3. The system of claim 2 further including a gyrocom
`pass on the marine vessel for producing a signal repre
`sentative of the true north heading of said marine vessel.
`4. The system of claim 3 further including means for
`determining the magnetic variations of the cable com
`passes and the marine vessel compass from the true
`north of said marine vessel’s heading.
`5. The system of claim 1 wherein the X-Y coordinates
`of said cable sensors are identi?ed as a plus X direction
`off the stern of the marine vessel and a plus Y direction
`off the starboard of the marine vessel.
`6. The system of claim 1 wherein said visual display is
`a cathode-ray tube.
`
`It
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`* * * *
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`Ex. PGS 1010