JPH0417398B2 - - Google Patents

Description

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a device for determining the position of a very long, elongated object submerged in water and towed by a ship, which device A plurality of measurement devices distributed along the object are used to measure its position in the water.

More particularly, the present invention relates to an apparatus for determining the location of an offshore seismic streamer, the apparatus comprising: a plurality of devices spaced along the length of the seismic streamer for measuring direction and depth; It consists of a connecting device placed inside this seismic windsock and for transmitting the measurements obtained to a central recording and processing system installed inside the ship.

Description of the Prior Art One known method for determining the true underwater position of a seismic streamer is formed from interconnected sections, each section including an array of seismic sensors and a transmission line. incorporating a direction measuring device such as a compass and a device for measuring hydrostatic pressure such as a pressure gauge or pressure gauge at regular intervals inside the
This allows us to know the direction of the earthquake streamer and its depth below the water surface at multiple locations, and as a result, determine its position behind the towboat.
The measurements obtained with these measuring devices are sent to a central recording and processing system located inside the ship.
The extracted seismic signals are recorded simultaneously, so that during the processing of the seismic records, the lateral drift of the seismic streamer relative to the direction of travel of the towing vessel can be taken into account, or the earthquake corresponding to the recording made You can define your profile. Such a device for determining the underwater position of seismic windsocks is described, for example, in French Patent No. 2 218 571.

These compasses should be located far away from the metal parts of the connections that interconnect the ends of the different sections of the windsock, as the readings from the compasses can be erroneous due to the presence of magnetic materials nearby. It is preferable to do so. In a first arrangement, these compasses are placed in the center of each section of the windsock and connected to the conductor. The case of each compass is inserted during installation into the external sheath of a windsock, for example, and is fixed in position, but expands to balance the hydrostatic pressure at the depth at which this sheath is operating, and As the diameter increases, for this reason the initial position is modified in an unpredictable manner and an uncertainty arises as to the true direction of the streamer section as measured by the compass.

There are also disadvantages in arranging the measuring devices within each section of the windsock. There are difficulties in accessing the interior of each section, and if, during use, there is a defect in the operation of the measuring device, the relevant windsock section must be completely replaced.

Additionally, if the measuring device includes pressure gauges, their arrangement within the sheath makes preliminary operation to test correct operation difficult. It must also be emphasized that since each section of the windsock must be compatible, the measuring device has to be integrated inside each section, which increases their price considerably, but especially for these This is true if the measuring device includes a compass.

According to a second arrangement method, the compass and other measuring devices are integrated into a rigid case inserted into each section of the streamer or between each section of the streamer.
Each case is made of non-magnetic material and its length is selected to be sufficient to avoid disturbances caused to the compass by the metal parts of the connections between the sections of the windsock. The positioning of the compass is more accurate in this case and the direction of the axis of the case is known with greater accuracy. Moreover, maintenance can be easily carried out by replacing defective sections. This arrangement has drawbacks, however. Other measuring devices such as pressure gauges are not accessible for direct testing performed during use. Such streamer sections or cases may be inserted if required, but if the number of sections or cases added is large, the overall length of the streamer increases greatly and the resulting overall streamer Modification of the distribution of seismic sensors along the line will result in changes in the obtained seismogram values.

In yet another arrangement, measurement instruments, such as depth sensors, are fixed on the outside of the flute at equal intervals along its entire length, and each for exchanging control and measurement signals with transmission lines inside the streamer. Associated with inductively coupled transmission devices are transformers whose windings are located on each side of the outer sheath of the windsock. Inductive connections require good magnetic coupling between the windings, which in turn requires precise positioning between the windings.

The present invention seeks to overcome these drawbacks of the prior art, and the technical problem to be solved is to set each measurement position of the windsock position at different positions along the windsock so that it can be easily attached and detached. The problem is how to place the windsock at a sufficient distance from the metal connections between the windsock sections.

SUMMARY OF THE INVENTION In order to solve this technical problem, a device for determining the position of a long elongate object (seismic windsock) according to the invention comprises a hollow body spaced along and outside said elongate object. , a measuring device for measuring the position of the elongated object within each of the hollow bodies and generating a signal indicative of the position;
a radio transmitting device located within each of the hollow bodies that emits radio waves modulated by the position signal; and a radio wave receiving device located within the elongated object that receives radio waves propagated through the water from the transmitting device. and a connection location for transferring the location data received by said radio wave receiving device to a central data recording and processing system.

A feature of this configuration is that the measuring device that measures the position of the windsock and generates a signal indicating the position is placed in a hollow body that is placed outside and along the windsock, and that the measurements obtained with the measuring device The value is sent by radio waves from the radio transmitter to the radio receiver located inside the windsock. That is, instead of relying on the principle of placing the measuring device inside the windsock to measure the position of the windsock, it is placed in a hollow body mounted outside the windsock close to the windsock sheath. .

In the present invention, with the above-described configuration, the measuring device is placed in a hollow body that can be easily attached to and detached from the windsock, so it is located at a position sufficiently far away from the metal connection between the windsock sections and not affected by the reception. The windsock section containing the device and the connecting device can be located in close proximity. Furthermore, since the hollow body is easy to attach and detach, the measuring device is easy to test and maintain, and is also easy to manufacture.

This elongated object is a digital seismic windsock and includes multiple acquisition devices, each of which multiplexes and collects signals received from multiple seismic sensors or groups of seismic sensors placed inside the flute. an interconnection device for transmitting the data supplied by the external measurement device to the acquisition device, in the case where these are digitized and transmitted sequentially via one or more lines to a central recording and processing system. Contains lines.

The advantage of such an arrangement is that the measuring device is always accessible, which makes it easier to adjust and calibrate, especially when it comes to compasses and pressure gauges. The receiving device of the transmitting device may be integrated systematically throughout each section of the windsock, whereas the generally more expensive measuring device is connected to each specific transmitting device and may be integrated more or less depending on the requirements. It may be installed in more or fewer sections. Adding measuring devices does not result in a modification of the overall length of the seismic flute since these measuring devices are mounted on the outer surface of the flute.

Furthermore, the use of radio wave transmission modulated by the signal to be transmitted allows a certain degree of freedom in the relative positioning of the corresponding transmitting and receiving parts of the different transmitting devices, which allows for adaptation to the windsock. It's convenient. Also, especially
If the transmitted data are digitized and encoded, a high degree of reliability and high accuracy can be obtained when transmitting the measured values obtained to the central system.

Adding the device of the invention to a windsock is rather easier if the windsock is of the digital type, and the measurement signal is transferred by means of local transmission lines to the acquisition device of the general system for transmitting seismic signals. Sent.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. (hereinafter referred to as a hollow body). These fixing devices consist of two sleeves 6, 7, each of which has a windsock section 5.
(FIG. 2) are formed from two shells 8, 9 arranged on each side of the sleeve and connected together by fixing screws 10, which sleeves are provided with longitudinal grooves 11.
is provided, and a tenon 12 integral with the hollow body 3 is provided in this groove.
are mated. The two sleeves 6, 7 are provided with an outer ring that is free to rotate relative to the seismic windsock, so that the axis of the hollow body remains in the vertical plane during rotational movements of the windsock about its longitudinal axis. You may choose to stay there.

A support member 42 is attached inside the hollow body 3, and a radio transmitting device 13 for transmitting the measuring devices 1, 2 and the signals generated by the measuring devices 1, 2 is attached to the supporting member 42.
is fixed. The battery of the accumulator 14 is also fixed to the support member 42 and supplies power to the measuring devices 1, 2 and the radio transmitting device 13. The antenna 15 is placed inside the seismic streamer near the location of the hollow body 3 and receives the signals transmitted by the radio transmitting device 13. The signal received by antenna 15 is transmitted by connecting member 16 to a nearby receiving device.

The transmitting device 13 includes, for example (FIG. 3) a switch 17, whose terminals are connected to the compass 1 and the pressure gauge 2, respectively, and whose common terminal is connected to a control and coding device 18. This device controls a switch 17 to alternately receive signals from one or the other of the measuring devices 1, 2, encode the received signals according to a particular code selected for transmission, and Give it an identification number.

The measuring devices are preferably of the digital type and are capable of transmitting the values they measure in the form of a series of encoded pulses. n
The angular value in degrees may be represented, for example, by a signal representing a series of n continuous pulses or a binary representation of this value.

The encoding in this case is the representation of the digital signals sent by each of the measuring devices in a BCD, ASCII, Gray code or other codes familiar to the expert. The identification number is, for example, a specific prefix that precedes each digital word.

Each encoded signal is then sent to a radio transmitter 19 associated with a transmitting antenna 20 . The frequency of the transmitted radio signal is selected to be extremely low (for example, on the order of 20 kHz). it is,
The digitized signal to be transmitted is modulated in response to forming a series of pulses. Modulation is, for example, changing the transmission frequency between two predetermined values f ₁ and f ₂ .

The receiving device 21 is connected to the antenna 15 by a connecting member 16 (FIG. 1), and includes a demodulator 22 that converts the frequency change of the received radio signal into a pulse signal. The demodulated signal is sent on the one hand to a common input of the switch 23 and on the other hand to a discriminator 24 which detects the identification number of the measuring device in each encoded series of transmitted pulses. A signal for controlling the switch 23 is generated. Depending on whether the received series of pulses relates to the compass 1 or to the pressure gauge 2, it is directed to a register 25 or to a register 26. The outputs of these two registers are connected to the inputs of two digital-to-analog converters (CNAs) 27, 28, respectively. The method of transmitting the analog voltages sent from the converters 27, 28 depends on the type of seismic windsock used.

The device of the invention may be combined, for example, with a digital seismic streamer, in which case the seismic streamer comprises a plurality of acquisition devices, each of which is received by a plurality of seismic sensors or a plurality of seismic sensor groups. Connecting the signals, digitizing them and transmitting them sequentially through one or more lines to a recording system, the acquisition devices being placed inside a rigid case inserted between the flute sections. Such a case is described, for example, in French Patent No. 2,471,088.

In the case shown in FIG. 3, the receiving device 2
1 is connected by a cable 29 to an auxiliary multiplexer 30 comprised in an acquisition device 31 located at one end of the windsock section, the other input of this multiplexer 30 also being connected to a central control and recording system. receive other analog signals to be sent to. The output terminal of the auxiliary multiplexer 30 is connected to one of the inputs of the main multiplexer 32, the other input receiving an analog signal sent from the seismic receiver RS. The output of the main multiplexer 32 is connected to the input of a digitizing and switching device 33 which communicates intermittently via one or more lines L with the central recording system.

A variation of the receiver described above is shown in FIG. 4, in which the output of demodulator 22 is connected directly to the input of a single digital-to-analog converter 34. The analog signal from this transducer 34 is activated by a switch 35 activated by the discriminator 24, depending on whether the decoded identification number relates to a direction measurement taken by a compass or to a depth measurement from a pressure gauge. and is sent to the first or second analog storage device 36, 37. Similarly, the outputs of analog storage devices 36, 37 are connected by cable 29 to local acquisition device 31.

The analog signal obtained at the output of the converter 27, 28 or 34 (in the embodiments of FIGS. 3 and 4) is reconverted into a digital signal by means of a local acquisition device 31 and a digital signal with which the device of the invention is combined. The digitization code selected for the type streamer is transmitted to the ship's central recording system. In this way, synchronization difficulties that appear when two different digitized codes have to be mutually aligned are avoided.

In the embodiment of FIG. 5, the encoding device 18 (FIG. 3)
This corresponds to the case where the encoding of the signal is carried out directly according to the code used to transmit the digitized seismic signals from different acquisition devices inserted over the entire length of the seismic windsock over the transmission line, and This corresponds to the case where a digital-to-analog conversion of the measurement signal generated by the compass or pressure gauge is not required. In this case, the output from the demodulator 22 is transmitted via a switch 23 controlled by a discriminator 24, depending on whether the decoded identification number is assigned to a compass or a pressure gauge. , are connected to the inputs of the first or second digital storage device 38, 39. The outputs of these two storage devices are connected directly to the two inputs of a switch 40 of the digitizing and switching device 33. The seismic receiver RS passes through the main multiplexer 32 and the digitizer 41, and then switches to this switch 4.
Connected to the other input of 0.

The device of the invention may also be combined with an analog seismic windsock, in which case the analog signals generated by different seismic sensors or groups of seismic sensors spaced along the length of the windsock are It is transmitted by a transmission line array to a recording system located on the towing vessel. In this case, the two transducers 27, 28 of each receiving device are connected to a particular line of this transmission line arrangement via a switching device (not shown) which is controlled by the recording system.

Since the distortion of the shape of the moving seismic windsock and the resulting change in the measured values by the measuring device are relatively slow, each compass 1 or each The time lapse between two successive interrogations of the pressure gauge 2 (FIG. 3) may be selected to be relatively long (1 second or more).

Also within the scope and spirit of the invention, analog measuring devices and analog-to-digital converters
It could be used to convert the measurements into digital words, or an acoustic transmitting and receiving device could be used to transmit the results of the direction and depth measurements into the interior of the seismic windsock.

[Brief explanation of drawings]

1 shows the arrangement of the hollow body with the measuring device on the outer surface of the seismic streamer; FIG. 2 shows details of the sleeve surrounding the seismic streamer to which the hollow body is rigidly mounted; 3 is a diagram showing a transmitting device related to the measuring device in the first embodiment, FIG. 4 is a diagram showing a receiving device inside the seismic windsock related to the measuring device in the second embodiment, and FIG. FIG. 3 is a diagram showing a receiving device inside an earthquake windsock associated with a measuring device in a third embodiment. In the figure, {1... compass, 2... pressure gauge} measuring device, 3... hollow body, {4... sheath, 5
... Earthquake windsock section, 6, 7 ... Sleeve} Long and thin object, 13 ... Transmitting device, 21 ... Receiving device,
29...Cable (connection device).

Claims (1)

[Scope of Claims] 1. A device for determining the position of an extremely long and slender object, such as a seismic streamer towed by a ship, comprising: a hollow body disposed at intervals along and outside the elongated object; , a device located within each of the hollow bodies for measuring the position of the elongated object and generating a signal indicating the position; and a device located within each of the hollow bodies for emitting radio waves modulated by the position signal. a radio transmitting device located within the elongated object and receiving radio waves propagated through the water from the radio transmitting device; and a central data recorder for storing position data received by the radio transmitting device. A device for determining the position of an elongated object, consisting of a connecting device for transfer to a processing system. 2. The device according to claim 1, wherein the elongated object is a digital seismic windsock and includes a plurality of acquisition devices, each acquisition device including a plurality of seismic sensors or a plurality of seismic sensors disposed inside the windsock. multiplexes, digitizes, and sequentially transmits the signals received by the seismic sensor array to the central data recording and processing system through one or more wires; a device for determining the underwater position of an elongated object, the device comprising a line for transmitting a signal taken up by and corresponding to the measurement data to said acquisition device; 3. Apparatus according to claim 2, wherein each line of said internal connection device is connected to said acquisition device via a multiplexing device, for determining the underwater position of an elongated object. 4. The device according to claim 1 or 2, wherein the measuring device is associated with each transmitting device and includes several measuring devices, and the transmitting device is configured to measure values measured by the measuring device. a frequency modulated radio wave transmitter, and a frequency modulated radio wave transmitter for continuously directing the signal generated by the measuring device to an input of the control and encoding device. A device for determining the underwater position of an elongated object, the receiving device comprising a device for demodulating the received signal, an identification device, and a second switch operated by the identification device. 5. The device according to claim 4, wherein the measuring device comprises a compass and a pressure gauge, and the device determines the underwater position of an elongated object. 6. The device according to claim 4, wherein the output terminal of the second switch is connected to a digital storage device and a device for converting a digital signal into an analog signal, for determining the underwater position of an elongated object. Device. 7. The device according to claim 6, wherein the storage device includes two digital registers each connected to an output of the second switch,
The converting device also includes two digital-to-analog converters connected to the outputs of the two registers, respectively, for determining the underwater position of an elongated object. 8. The apparatus of claim 6, wherein the conversion device includes a digital-to-analog converter for converting the received signal into an analog signal, and the storage device is connected to the output of the second switch. Apparatus for determining the position of an elongated object in water, including two connected analog storage devices, the input of said second switch being connected to the output of said digital-to-analog converter. 9. Apparatus according to claim 4, wherein the output terminal of the second switch is connected to a digital storage device for determining the position of an elongated object in water. 10. The device according to claim 1, wherein the measuring device determines the underwater position of an elongated object, which is supported by the elongated object and is located inside a hollow body that is always held in a vertical position. device to do.