`
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`Page 1 of 1 1
`
`RAY-1005
`
`Aug- 11, 1964
`
`7
`
`H. E. LUSTIG ETALV
`RADIATION MAPPING SYSTEM
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`
`3,144,631
`
`Filed Jan. 9, 1962
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`Page 2 of 11
`
`RAY-1005
`
`Aug. 11, 1964
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`
`Filed Jan. 9, 1962
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`H. 5. LUSTIG ETAL
`RADIATION MAPPING SYSTEM
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`H. E. LUSTIG ETAL
`RADIATION MAPPING SYSTEM
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`Filed Jan. 9. 1962
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`3,144,631
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`Page 3 of 11
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`Page 4 of 11
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`Aug. 11, 1964
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`H. E. LUSTIG ETAL
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`RAY-1005
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`Page 5 of 11
`
`3,144,631
`Patented Aug. 11, 1964
`
`United States Patent Office
`
`1
`
`3,144,631
`RADIATION MAPPING SYSTEM
`Howard E. Lustig, Flushing, and Arthur L. Rossofi, Hunt-
`ington Station, N.Y., and Paul D. Frelich, Wellesley,
`and Harold K. Farr, Westwood, Mass, assignors to
`General Instrument Corporation, Newark, N.J., a cor-
`poration of New Jersey
`Filed Jan. 9, 1962, Ser. No. 165,173
`22 Claims.
`(Cl. 340—3)
`
`The present invention relates to a system for mapping
`an area from a mapping station moving thereover, the
`mapping station emitting radiations which are reflected
`from the area to be mapped and which are then detected
`by appropriate equipment carried by the mapping sta-
`tion. The invention is here specifically disclosed in con-
`junction with a shipborne system for mapping the contour
`of the sea bottom by means of sonar radiations, but the
`invention is not specifically limited thereto. Purely by
`way of example, it is equally applicable in many respects
`to an airborne radar ranging method for mapping the
`terrain over which the aircraft flies.
`Mapping of the ocean bottom through the use of sonar
`is not a new concept. However, the systems which have
`heretofore been employed for that purpose have inher-
`ently limited the use of such a method, either because of
`lack of accuracy and definition, because of extreme
`limitations on the speed at which the mapping vessel
`could move, or both.
`In addition, the nature of such
`systems has made it
`impractical
`to provide accurate
`compensation for such aberrational movements of the
`mapping station as changes in speed, changes in depth
`(in the case of submarines), roll, pitch and the like.
`to
`One proposal which has been made in the past
`solve at least some of these problems is to utilize a single
`relatively narrow sonar beam emanating from the map-
`ping station, that beam scanning from side to side over
`a given strip area of the sea bottom and being employed
`both for transmission of radiations and for reception of
`reflections from the sea bottom. Because of the rela-
`tively slow speed with which sound moves through water,
`this use of a single beam for transmission and reception
`of the appropriate radiations necessitates a relatively slow
`scan, the necessary scanning time increasing as the depth
`of the sea increases, and thus places prohibitive restric-
`tions on the speed at which the vessel can move in
`mapping an area of the sea bottom.
`By way of contrast the system of the present invention
`utilizes separate beams for transmission and reception
`respectively,
`thus dividing the burden of directivity be-
`tween the two beams and hence greatly simplifying design.
`Moreover,
`the construction and arrangement of these
`beams are such as to permit the vessel to move at reason-
`able cruising speed without any loss in map coverage.
`In addition,
`the arrangement of
`the individual trans
`mitting and receiving beams in the system of the present
`invention permits the ready compensation of the system
`for roll and pitch of the vessel.
`In the proposed system the transmitted beam is in
`the shape of a thin fan lying in a downwardly extending
`plane preferably perpendicular to the heading of the ship,
`the angular width of that fan beam being sufficiently
`greater than the area of the bottom which is to be mapped
`so as to take into account roll of the ship. Thus, there
`is no need to compensate the transmitted beam for ship
`roll. Means are provided, however, for compensating
`the transmitted beam for ship pitch,
`thereby ensuring
`that the transmitted beam is always directed in its desired
`direction, generally vertically oriented. This fan shaped
`beam, which may be 90° wide and 1" thick, illuminates
`a long narrow area of the ocean floor lying perpendicular
`to the ship’s heading, and as the ship progresses, suc-
`
`CI
`
`10
`
`15
`
`20
`
`25
`
`3O
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`7O
`
`2
`cessively narrow areas of the ocean floor are illuminated
`thereby, thus producing a substantially continuous map-
`ping coverage of a strip of the sea bottom.
`Reflected radiations are received by the mapping sta—
`tion in a plurality of closely spaced narrow downwardly
`extending fan-shaped beams the planes of which are
`preferably oriented substantially perpendicular
`to the
`transmitting beam, and hence substantially parallel to the
`fore-and-aft direction of the ship. Thus, each of the
`individual receiving beams will cover a thin narrow area
`of the ocean floor, the areas corresponding to adjacent
`receiving beams lying side by side on the ocean bottom
`and collectively being intersected by the transmitting
`beam. Since the receiving beams each cover areas which
`are longer in the fore—and-aft direction of the vessel than
`the thickness of the transmitting beam, forward move-
`ment of the ship does not interfere with reception, and
`in addition there is no need to compensate the receiving
`beams for pitch of the ship. Roll of the ship will, how-
`ever, move the areas sighted by each of the receiving
`beams laterally over the sea bottom, so that roll com-
`pensation is desirable.
`In the instant system this is
`accomplished by utilizing receiving beams which,
`in
`number and placement, cover a lateral distance on the
`ocean floor greater than that to be mapped. As the ship
`rolls only those beams are selected which cover
`the
`specific area of the ocean floor which is to be mapped;
`the other beams are unused insofar as the instantaneous
`production of the signal representing the contour of the
`ocean floor is concerned.
`the transmitting beam
`As here specifically disclosed,
`emanates from a transmitter comprising a plurality of
`individual transmitting elements arranged longitudinally
`on the ship’s hull, and the reflected radiation receiver
`comprises a plurality of
`individual
`receiver elements
`arranged laterally on the ship’s hull. Pitch control for
`the transmitting means is accomplished by controlling the
`phasing of the radiations emanating from each of the
`individual projector elements. As has been mentioned,
`roll compensation for the receiving means is accom-
`plished by selecting those of the individual receiver ele-
`ments which are associated with the appropriate receiv-
`ing beams corresponding to the area to be mapped.
`Since the ship's hull is usually curved, the laterally ar-
`ranged individual receiver elements, if they conform to
`the hull, would not be in a common plane.
`In order to
`compensate for such departure from a planar configura-
`tion, when it exists, the individual signals produced by
`the individual receiver elements have their relative phases
`adjusted so that,
`insofar as the display means is con-
`cerned, they are all at the same effective distance from a
`reference plane perpendicular to the direction of the
`desired receiving beam.
`Through the use of the present system an accurate
`representation of an appreciably wide area of the sea
`bottom can be produced and complete coverage of the
`sea bottom over
`that
`longitudinally projected area is
`possible with the ship moving at cruising speed or even
`at high speed, thus permitting extensive areas of the sea
`bottom to be continuously mapped in an accurate and
`effective manner.
`To the accomplishment of the above, and to such other
`objects as may hereinafter appear, the present invention
`relates to a system for mapping through the use of trans-
`mitted and reflected radiation as defined in the appended
`claims, and as described in this specification, taken to-
`gether with the accompanying drawings in which:
`FIG. 1 is a schematic View illustrating the scanning of
`a single narrow laterally oriented strip of the sea bottom;
`FIG. 2 is an idealized representation of one way in
`which the profile of the scanned strip of the sea bottom
`
`

`

`IJKLMNNO
`PQRSTUTVWTMM
`
`3,144,631
`
`3
`could be reproduced on the face of a cathode ray tube;
`FIG. 3 is a diagrammatic perspective View of the ori—
`entation of
`the respective transmitting and receiving
`beams;
`FIG. 4 is a diagrammatic plan View illustrating a typical
`location of the transmitting and receiving means on the
`ship’s hull, and also showing the location relative thereto
`of the areas on the sea bottom covered by the trans—
`mitted beam and a selected few of the receiving beams;
`FIG. 5 is a diagrammatic cross sectional view showing
`one location of the receiving means on the ship’s hull;
`FIG. 6 is a schematic View indicating the manner in
`which the projecting beam may be stabilized for pitch;
`FIG. 7 is a schematic View indicating the problem
`involved in the reception of reflected radiations by indi-
`vidual
`receiving elements located at different vertical
`heights; and
`FIG. 8 is a block diagram of the electronic systems
`ma
`involved in transmission and reception of the radiation.
`
`General Description
`
`This invention will be here specifically disclosed as
`embodied in a mapping system carried by a surface ves-
`sel 2, designed to map the bottom of the sea, generally
`represented at 4, and using sonar radiations to accom-
`plish that result.
`It will be understood that the vessel 2
`could be a submarine (in which case computation of the
`depth of the floor 4 below sea level, generally designated
`6, would have to take into account the depth of the sub-
`marine at the time that the mapping operation is per-
`formed), and that in its broader aspects, a comparable
`type of mapping operation could be carried out utilizing
`other types of radiated energy, for the mapping of other
`types of areas, and with other types of movable map-
`ping stations (e.g. airborne radar mapping of the exposed
`surface of the earth).
`As schematically represented in FIGS. 1 and 2, a dis-
`play representation of the profile of a narrow area of
`the sea bed can be produced on the screen 8 of a cathode
`ray tube or the like. Taking the situation shown in FIG.
`1, Where the ship 2 is shown at position 0 and is assumed
`to be moving out of the plane of the paper, the ship 0
`scans the sea bottom 4 by means of transmitted radia—
`tions (usually sonar radiations for undersea work), and
`detects radiations reflected therefrom,
`identifying those
`radiations in terms of range r (time delay between trans-
`mission and reception) and lateral location (angular rela-
`tionship a of the reflected radiation relative to a fixed
`standard, usually the vertical). Thus radiation reflected
`from the point P in FIG. 1 will be detected by the sonar
`equipment on the ship 2 and the location of the point
`P can be accurately determined by trigonometric com-
`putations. An analog of the actual situation as repre-
`Sented in FIG.
`1 can be created in known manner on
`the cathode ray tube screen 8, as indicated in FIG. 2,
`thus producing on the face of that screen a visible trace
`4’ which will correspond to the profile of the area 4
`of the sea bottom then being scanned.
`It is assumed that the area of the sea bottom 4 to
`be mapped extends laterally between points A and B,
`subtending an angle of 60" at point 0.
`If only that 60°
`angle is scanned,
`then roll of the ship will cause the
`points A and B tomove laterally over the sea bottom,
`thus mapping an area different from that which should
`be mapped. Accordingly, the profile actually illuminated
`by the transmitted radiation is shown as extending between
`points C and D, subtending an angle of 90° at point 0.
`In this manner the 60° portion centered on the vertical
`3 is always illuminated as long as the ship’s roll does
`not exceed 15° in either direction.
`In accordance with the present invention as here spe-
`cifically disclosed, and as shown particularly in FIGS. 3
`and 4, the sonar energy emanating from the ship 2 is
`transmitted in the form of a thin fan beam 5A lying in a
`substantially vertical plane perpendicular to the heading
`
`10
`
`15
`
`20
`
`25
`
`4O
`
`45
`
`55
`
`60
`
`65
`
`70
`
`75
`
`4
`of the ship. This beam, which is 90" wide (for reasons
`indicated above and illustrated in FIG. 1) and which may
`be approximately 1°
`thick,
`illuminates a long narrow
`area of the ocean floor, as indicated at 5B in FIGS. 3
`and 4, this area 5B extending perpendicular to the ship’s
`heading. As the ship progresses,
`this illuminated strip
`SB sweeps out into an area determined by the speed
`and direction of movement of the ship 2. To form the
`transmitting beam,
`the transmitter 10 may be located
`on the ship’s hull at a position such as is illustrated in
`FIG. 4, and may be composed of a plurality of individual
`transmitter elements 10a arranged longitudinally on the
`hull as indicated.
`For receiving transmitted radiations which are reflected
`from the sea bottom or other terrain being mapped, a
`plurality of individual fan-shaped receiving beams, gen-
`erally designated 12, are employed. The planes of these
`beams are oriented substantially perpendicular to the
`transmitted beam 5A, that is to say,
`they are narrow
`(approximately 1°) widthwise of the ship 2 and are long
`(extending 7° to either side of the nominal vertical axis
`3 of the ship 2) in the fore-and-aft direction of the ship
`2. The beams 12 sight adjacent areas 14 on the sea
`bottom, the areas 14 intersecting the area SE at 16.
`If, as indicated in FIG. 1, a 60° width in scanning
`may be desired, sixty receiving beams 12, each of 1"
`Width, would then be required. However, if this were
`‘ all
`that were done, roll of the ship 2 would laterally
`translate the beams 12, so that not all of them would
`30
`intersect with the strip SB at the proper points 16.
`In
`order to eliminate this disadvantage, the beams 12 should
`collectively subtend at point 0 a lateral angle greater
`than 60°, such as 90° (thus involving the use of ninety
`receiving beams 12 each 1° wide). This will permit a
`roll of the ship 15° in either direction, as indicated in
`FIG. 1, while at the same time providing the desired
`number
`(e.g. 60) of individual receiving beams 12 to
`intersect the illuminated area 5B.
`Means 48 are provided to select those sixty receiving
`beams 12 which intersect the area 5B between the points
`A and B at any given moment, and to use the energy
`derived from those selected beams 12 to produce the dis-
`play analog 4’.
`The receiver array, generally designated 18, may be
`located on the ship 2 in a manner indicated in FIG. 4,
`arranged laterally relative to the length of the ship.
`Because the length of the beams 12 (measured in the
`fore-and-aft direction of the ship 2) is greater than the
`corresponding dimension of the transmitted beam 5A,
`pitch of the ship 2, within limits, will not have any ad-
`verse effect upon the operation of the system insofar as
`reception is concerned, since, as may clearly be seen from
`FIG. 3, considerable longitudinal movement of the areas
`14 is permissible without destroying their intersection with
`the area 5B.
`
`The manner in which the analog display 4’ is used may
`be varied widely. A series of such display analogs may
`be photographed or otherwise reproduced, and appropri-
`ate maps synthesized therefrom. Alternatively, and as is
`preferred, the display analogs 4’ may be used to produce
`a contour map representation directly, in a manner such
`as is.disclosed, in the copending application of Howard E.
`Lustig and Arthur L. Rossofl, Serial Number 165,064,
`entitled, “Contour Mapping System,” filed on January
`14, 1962, now abandoned, and assigned to the assignee
`of this invention. However, the precise manner in which
`the display analog 4’ is used forms no part of the present
`invention.
`Transmitter
`
`The physically fixed transmitter 10 is formed of a
`plurality of individual transmitting elements 10a which
`may be placed on the bottom of the hull 2 and aligned
`parallel to the longitudinal axis of the ship. One hundred
`and eight individual elements 10a may be employed, each
`having a radiating area ,2” wide and 2%” long in the
`RAY-1005
`
`Page 6 of 11
`
`
`
`

`

`XYZ[\]]^
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`
`Hence, the rotation angle of the output shaft 34 of a
`pitch servo 36 can be represented as ¢1=(27ra/>\)
`0,
`which is just proportional to the pitch angle 0, therefore
`the pitch servo 36 can drive the first resolver 32 directly
`and successive resolvers 32 through gear ratios having
`simple integral values 2, 3,
`.
`.
`. 18 (corresponding to 11)
`(see FIG. 6). As a practical matter it is preferable to
`use the higher speed shaft,
`(p18, rather than oi, as the
`input pitch signal and then to gear down to all the other
`channels. The number 18 is one—half the total number
`of channels. The remaining 18 channels (numbered 0,
`—1, —2,
`.
`.
`. —17) can be driven from the same shafts
`by reversing the leads on one of the quadrature com-
`ponent inputs to the resolvers. The number zero chan—
`nel is electrically energized without phasing.
`Receiver
`
`The receiver array 18 which is used to sense the re-
`turn echo determines the directivity of the sonar system
`in the athwartship direction.
`It is capable of defining a
`thin fan beam 12 which is about 1° wide in this direction
`and 14° wide in the fore-and-aft direction. Phasing net—
`works simultaneously generate 90 such (preformed)
`beams, spaced at intervals of 1" along the length of the
`strip 5B illuminated by each transmitted pulse.
`The location of the array is determined by the require-
`ment, on the one hand, that it be near enough to the cen-
`ter of the ship to permit the use of a large array and, on
`the other hand, that it be far enough forward to avoid
`excessive engine noise. FIG. 5 shows a suggested in-
`stallation.
`It consists of a narrow belt of individual re-
`ceiving elements 18a disposed across the underside of the
`hull. The belt is 18 inches wide in the fore-and-aft direc-
`
`RAY-1 005
`
`Page7of11
`
`3,144,631;
`
`6
`fathoms, and further, that the bottom is flat and is 3000
`fathoms down. Ship’s speeds up to
`22.1 X 3000/4000:l6.5 knots
`
`can then be used for full coverage of the bottom area.
`If the bottom were 1500 fathoms down, the ship could
`proceed either at up to 8.25 knots, or change the repeti-
`tion rate to correspond to 2000 fathom maximum depth
`and then proceed once more at 16.5 knots.
`In the limit-
`ing case, where the desired maximum depth coincides
`with the actual depth, a speed of 22.1 knots still yields
`100% coverage.
`In other words, with prior knowledge
`of the bottom, a pulse repetition rate can be selected
`which will allow the vessel to cruise at normal and even
`high speeds.
`The transmitted beam 5A is stabilized electronically
`so as to remain in the true vertical plane regardless of
`pitching of the ship. The beam steering necessary for
`stabilization is accomplished by the phasing scheme in-‘
`dicated in FIGS. 6 and 8. As here specifically disclosed,
`the 108 elements 10a in the transmitter array are divided
`into 36 groups of three elements each. Each group is
`powered by a separate driver 26. The actual phasing is
`accomplished with resolvers 32 operating at low power
`levels’. This method provides precise and smooth control
`of phase, and eliminates the problems associated with
`complex compensator plates and delay lines.
`If 0 is the angle of pitch, then the beam should be
`steered by an amount 9, and transmitter group number n
`(where It
`is counted from the center of the array 10)
`should introduce a phase shift
`(fin: (27rn‘a/A) Sin 9
`where a is the spacing between groups of elements (which
`may in practice amount to 8”) and )\. is the wave length
`of the radiations in water. The pitch in sea-state 3 or 4
`is about 135°. Hence, within the practical range of 0
`values, We can replace sin 0 by 0 with an error of less
`than 8 seconds of arc. The angle of rotation of resolver
`32 for transmitter group n is then
`gun: (271mm) 9=n¢1
`
`5
`direction of the axis of the array. The total length of
`the array may be 24 feet. For an operative frequency
`of 12 kc. this will produce a fan-shaped transmitting beam
`4A that subtends an angle (measured at the —3 db points)
`of approximately 1°
`in the fore—and-aft direction and
`90° in a direction perpendicular to the ship’s heading.
`Each of the transmitting units 10a may be actuated by
`circuitry (see FIG. 8) including an oscillator 20, ampli-
`fier 22, phasing circuits 24 and drivers 26.
`. The oscillator 20 is of the variable frequency type, and
`may be adjusted, as indicated at 28, to modify the fre-
`quency of the transmitted indications.
`It is desirable
`that this be done to compensate for variations in the speed
`of propagation of those radiations through the water as
`the temperature of the water varies, thereby maintaining
`the wavelength of the radiations in the water constant.
`A keying pulse 30 is used to initiate pulse transmission
`from the elements 10a at the proper repetition frequency
`and power level.
`The repetition frequency, and its relationship to the
`depth of the sea and the forward speed of the ship 2,
`may be appreciated from the following analysis:
`For any desired maximum depth, the interval between
`pulses will be determined by the maximum slant range
`involved, which occurs for the beam looking farthest to
`the side. Here,
`
`where
`
`Rmax=Dmax/COS 1i’max
`
`Dmax is the specified maximum depth to be mapped (ref-
`erence depth)
`311mm; is the maximum side looking angle to be used, and
`Rmax is the resulting maximum slant range.
`
`The resulting ping interval, which sets the pulse repetition
`rate, is:
`.
`Tp=2DmEx/c cos wmax=2Rmax/c
`where c is the velocity of sound.
`This time, within which all possible returns will come
`back from the bottom, affects the permissible forward
`speed of the ship. Consider the distance along the bot-
`tom subtended by the transmitted fan beam in the fore-
`and-aft direction. This distance is D6/cos 1//, where D
`is the actual depth, 0 is the fore-and-aft beam width (in
`radians), and 5b
`is the side looking angle. Note that
`D/cos tb=R is the slant range to the bottom. There
`exists some point at the bottom for which this slant range
`is a minimum.
`The time required for the ship to travel the forward
`distance subtended by the beam at this minimum slant
`range is given by
`
`[=0Rmin/V
`
`where v is the speed of the ship expressed in the same
`linear dimensions as Rmm.
`If the speed of the ship is
`such that t is equal to T1,, then 100% coverage of the bot—
`tom will result: that is, successive pings will illuminate
`areas that are adjacent.
`If the speed is such that t is
`greater than or less than TD, then overlapping or else less
`than 100% coverage of the bottom respectively, will re-
`sult.
`,
`-.
`.
`,
`f Therefore, at least 100% coverage will be guaranteed
`if the following conditions hold:
`
`i HRmin/ YZZDmax/C COS lz’rnax
`13y rearrangement, the following limitations on ship’s
`speed apply for 100% (or greater coverage).
`
`> VgceRtnin COS Wmax/ZDmax
`For 6=1°=.0174‘5 ‘radian,
`\l/maxz3002
`'
`knots,
`'
`-
`v<22.1 (Rmm/Dmax) knots
`
`and c=2922
`‘
`
`‘ This can be interpreted as follows: suppose the system
`repetition rate is set to cover a maximum depth of 4000
`
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`55
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`60
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`(i5
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`

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`
`3,144,631
`
`10
`58 are fed, Via matching transformers 62, to receivers 64.
`The receivers 64 amplify and detect the beam signals
`(usually the received pulse in each beam with the greatest
`amplitude) and pass them on to the scanning commutator
`66. The scanning commutator 66 periodically and rapid-
`ly samples in sequence the output of each receiver.
`Whenever a signal has been detected in any one re-
`ceiver the scanning commutator 65 transmits an impulse
`to video amplifier 68.
`Impulses from the video ampli-
`fier go to the grid of the cathode ray display tube, whose
`deflection system is in synchronism with the scanning
`commutator 66 to form the display analog 4’.
`Corrections
`
`In addition to corrections for pitch and roll as already
`described corrections may be made in any appropriate
`manner to compensate for such aberrational movements
`of the ship 2 as changes in speed, yaw, drift, heading
`and course changes, rapid lateral displacements, and in-
`correct navigational data. A preferred manner of ac-
`complishing some of these corrections, particularly when
`strip mapping and/or direct contour map generation is
`involved, are disclosed in the aforementioned copending
`patent application, Ser. No. 165,064, of Lustig and Ross-
`off. Compensation for changes in the depth of the arrays
`10 and 18 (such as accompany pitching of the ship 2,
`changes in its depth if it is a submarine, or changes in
`its altitude if it is an aircraft), and for variations in sound
`velocity in accordance with the depth of the water through
`which it passes can also be made.
`Conclusion
`
`9
`coming wave front can be used as a reference. Thus
`knowing d1, the relative phase delay in the water, (#1 can
`be determined.
`It will be a function of frequency and
`sound velocity and is given by
`(15,1411fo 360/c (degrees)
`
`is the element number, d, is measured in feet,
`where z'
`0 in feet per second, and f in cycles per second.
`Now let us define the phase shift made possible by the
`bridging resistors 40 at the output of the four phase
`preamplifier as 0,.
`For each element in the array, 0, is adjusted so that
`(#1 plus 01 is equal to a whole number of cycles. That is,
`¢,+o,=n360°
`
`where n is an integer. All the bridging resistors 40 are
`tied to a common summation point, at which a beam be-
`comes available, pointing in the particular direction for
`which the various 4:, were computed. Other bridging
`resistor sets can be computed for other angles of arrival
`and connected to the multiphase preamplifier outputs.
`From the equation given for 43,, it can be seen that the
`phase shift will vary when the local sound velocity varies.
`This could amount to :3.5% from the polar regions
`to the equatorial regions and, if left uncompensated, could
`seriously reduce and broaden the main lobe and bring
`up the side lobes. Fortunately, a corresponding percent-
`age change in the operating frequency compensates for
`the velocity change. Therefore, the outgoing frequency
`will be controlled by a calibrated variable frequency os-
`cillator 20. The frequency control dial indicator 28 will
`be calibrated directly in local sound velocity. A recessed
`trimmer 42, a 12 kc. crystal oscillator 44, and a zero beat
`indicator 46 will be used to check calibration.
`Ninety preformed beams 12 will be formed for a total
`look of 45 ° to either side. A uniform beam spacing of
`1° from beam center to beam center will be employed.
`The first beam 12 that looks to the left will be depressed
`895° relative to the deck plane as will be the first beam
`12 that looks to the right. The second beam 1‘2, either
`right or left, will be depressed 885°,
`the third 87.5 °
`etc., until the 45th beam 12, which will be depressed
`45.5 °
`Signals from all 90 beams 12 are applied to the roll
`compensator 48 via matching transformers 50. The pur-
`pose of the roll compensator 48 is to select from the 90
`available preformed beams 12, those 60 beams 12 which,
`at any instant, are closest to the vertical.
`The roll compensator 48 may comprise a capacitor
`switch having a stator 52 and a rotor 54. The stator
`may comprise an insulating flat plate about 10 inches in
`diameter with 90 individual printed circuit sectors 56,
`each 3 degrees wide, distributed evenly over an arc of
`270 degrees. The rotor 54 will be similar, but will have
`60 printed sectors 53, each 3 degrees wide, covering a
`total arc of 180 degrees. The remaining 90 degrees of
`the stator and 180 degrees of the rotor surface will be at
`ground potential. The rotor may be mounted parallel
`to the stator at a separation of 001 inch.
`The angular scale factor of the compensator has been
`multiplied by 3 to utilize the available capacitance more
`fully. A given roll angle is thus compensated by turning
`the rotor 54 just 3 times as much. Rolls of :15 degrees
`will be compensated for in the present design by turning
`the compensator rotor 54 :45 degrees. Since the com~
`pensator rotor 54 never makes a complete revolution,
`slip rings will not be necessary. Sixty flexible leads are
`used to bring the rotor signals out. The rotor 54 is posi-
`tioned by a servo mechanism 60 driven by synchro sig-
`nals from the ship’s gyro system representing the ship’s
`roll. The capacitive commutator 48 is capable of con-
`necting an output proportionally to two adjacent beam
`inputs. This makes it possible to obtain continuous and
`smooth roll compensation.
`The beam signals applied to each of the rotor sectors
`
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`The system of the present invention can be used for
`continuous, effective and accurate mapping of terrain
`from a mapping station moving over that terrain at an
`appreciable speed. The design and manner of coopera-
`tion of the various parts greatly facilitates their con-
`struction and use, minimizes the power requirements of
`the system, simplifies some of
`the corrections which
`should be applied for the attainment of a proper degree
`of accuracy, and eliminates the need for certain correc-
`tions.
`The specific construction of the various elements in-
`volved, and the specific design of the several electrical
`circuit components, may be varied widely, and may take
`known forms. Accordingly they have been here disclosed
`schematically or in block diagram form.
`Although only a single embodiment of the present in-
`vention has been here specifically disclosed,
`it will be
`apparent that many variations may be made therein, all
`within the scope of the invention as defined in the fol-
`lowing claims.
`We claim:
`1. A system for mapping an area from a mapping sta-
`tion moving over said area which comprises means for
`transmitting a beam of energy from said station, said
`beam being wide in a first direction and narrow in a
`second direction at right angles to said first direction,
`means for receiving transmitted radiation reflected from
`said area in a plurality of adjacent individual receiving
`beams, said receiving beams being wide in said second
`direction, narrow in said first direction and arranged
`relative to one another in said second direction, and
`means for recording signals received in each receiving
`beam, said receiving means comprising an array of a
`plurality of individual
`transducing elements of greater
`number than the number of said beams, more than one of
`said elements being operatively associated with one an-
`other to produce reception in a given beam.
`2. The system of claim 1,
`in which said receiving
`means comprises a plurality of individual receiving ele-
`ments located in a non-planar array, and means opera-
`tively connected between said receiving elements and said
`recording means for compensating for the departure in
`positions of said receiving elements from a planar array.
`
`RAY-1005
`
`Page 9 of 11
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`Page 10 of 11
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`in which said receiving
`' 3. The system of claim 1,
`means comprises a plurality of individual receiving ele-
`ments located in a non-planar array, and means opera—
`tively connected between said receiving elements and said
`recording means for compensating for the departure in
`positions of said receiving elements from a planar array