Sonar is frequently used in marine vessels. Sonar uses sound propagation to communicate with or detect objects on or under the surface of water. Existing sonar techniques include active sonar, which includes emitting pulses of sound and listening for echoes.
However, the marine industry lacks existing active sonar systems that perform active sonar detection efficiently and effectively in the aft of a moving marine vessel.
In some embodiments, the methods (and systems) may generate, from the aft direction of a marine vessel, one or more pulses of sound. The methods (and systems) may receive, at the aft direction of a marine vessel, one or more echoes, in response to the generated one or more pulses of sound interacting with one or more physical objects. The methods (and systems) may perform an analysis on the received one or more echoes based upon the generated one or more pulses of sound.
According to some embodiments of the methods (and systems), the analysis may be performed based upon space-time Doppler filtering to detect range and direction of at least one of the one or more physical objects. The one or more physical objects may include game fish. The one or more physical objects may include a plurality of physical objects including one or more target objects and one or more reference objects.
According to some embodiments of the methods (and systems), the analysis may be based upon at least one of the size and location of at least one of the one or more physical objects. The analysis may include one or more of acoustic detection, localizing, tracking, and sizing of at least one of the one or more physical objects. The analysis may be based upon estimating depth of at least one of the one or more physical objects. According to some embodiments of the methods (and systems), the methods (and systems) may display live video of at least one of the one or more physical objects. The methods (and systems) may display at least one of depth and temperature of a dredge attached to the marine vessel. The methods (and systems) may generate the one or more pulses of sound from at least one of below and astride the marine vessel. The methods (and systems) may generate the one or more pulses of sound from first and second sound sources. The second sound source may be connected to a dredge connected to the marine vessel.
In some embodiments, the systems (and methods) may include at least one processor coupled to associated memory, the at least one processor configured to implement one or more of a generation module, a receiving module and/or a processing module. In some embodiments, the systems (and methods) may include the generation module configured to generate, from the aft direction of a marine vessel, one or more pulses of sound. In some embodiments, the systems (and methods) may include the receiving module configured to receive, at the aft direction of a marine vessel, one or more echoes, in response to the generated one or more pulses of sound interacting with one or more physical objects. In some embodiments, the systems (and methods) may include the processing module, configured to perform an analysis on the received one or more echoes based upon the generated one or more pulses of sound. According to some embodiments of the systems (and methods), the analysis may be performed based upon space-time Doppler filtering to detect range and direction of at least one of the one or more physical objects.
The foregoing will be apparent from the following more particular description of example embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments.
A description of example embodiments follows.
The teachings of all patents, published applications and references cited herein are incorporated by reference in their entirety.
Some embodiments are directed to an AFT-Looking Sonar, which may include sonar mounted to a marine craft (preferred is a surface craft, but it may be otherwise), aimed in the aft-direction. Sonar may be mounted on a vessel door, stern, or aft of a vessel, or in any other manner known to one skilled in the art. According to some embodiments, the stern and aft are at the back or tail portion of the vessel, and stern is outside or offboard, while the aft is inside or onboard. The purpose is to use active sonar to Detect, Localize, Track and/or Classify (DLTC) objects behind the marine craft. The target objects for this system may be a towed group of fishing lures that are deployed from the stern, along with the large fish that attack the lure(s). In marine parlance these are called fishing dredges.
In the art, there are at least two kinds of dredges:
1. those that drag the bottom to catch (scoop up) shellfish, and
2. the other kinds that stay in the water column or near the surface and have lures and fishing hooks attached. Some embodiments may use active sonar to detect, localize, track and/or classify (DLTC) objects on the second kind of dredge, and the speeds are usually from 1 to 5 knots.
Examples existing in the art of underwater videos showing a dredge being towed at low speed, and being chased by some very large predatory game fish. Other example videos known in the art show how dredges are deployed from a boat.
As illustrated in
The one or more physical objects may include predatory game fish. The analysis may be based upon the size of at least one of the one or more physical objects. The analysis is based upon the location of at least one of the one or more physical objects.
As illustrated in
As illustrated in
Computer control 202 (including but not limited to any reference to “computer control” herein) may provide or control wave parameters to the signal generator 206 such as modulation, bandwidth, start and end frequency, pulse duration, pulse repetition frequency (PRF), amplitude, duty cycle, as well as calculate, filter, estimate and use noise estimates, and/or detection parameters. Preferred frequencies may be ultrasonic (greater than 20 kHz) for small wavelengths and narrow beams but less than 1 MHz to have useful range in marine environments. The signal 210 output from the signal generator 206 may be multiplexed 214a on its way to one or more amplifiers 218. The one or more amplifiers may output one or more electrical pulses 222 that may pass through 226 a multiplexer 214b and be transducted into sound by N-channel acoustic arrays 230 that may perform tuning 236 on the electrical pulses 226. The one or more N-channel acoustic arrays 230 (including but not limited to any reference to “arrays” herein) may output one or more signals 238 (susceptible to random acoustic noise 240 and random EMI noise 252) that may be mixed to baseband 244 and analog filtered 248, the filtered output 254 being forwarded to pre-amplifiers 256. Electromagnetic interference (EMI) 252 can occur anywhere in the signal path but it is shown between transducer array 230 and preamps 256. The output 258 of the preamplifier 256 may pass through analog filters 260 before being received 262 by one or more analog-to-digital converters (ADC, element 264). In
The acoustic array 230 may be used to generate output acoustic pulses 276 to one or more physical objects 284, and an acoustic echo 280 may be received based upon interaction with the one or more physical objects 284. Sizing, or determining a size of the one or more physical objects 284, may be achieved based upon the magnitude of the received echo 280.
Although not shown in
As illustrated in
The additional sound sensor 382 provides multiple advantages. The additional sound sensor 382 is advantageous in that it is less influenced by movement (pitch, heave, yaw etc.) of the vessel 370. As such, the additional sound sensor 382 is a more stable device for the transmission and reception of sonar pulses. The additional sound sensor 382 may be advantageous in heavy sea conditions or for smaller vessels 370 for fishing. In addition, the additional sound sensor 382 also provides the opportunity for sensor data fusion (a boat-mounted sensor 380 and a towed sensor 382) which can reduce false alarms and clutter by having two sensor systems (boat sensor 380, towed sensor 382) that look at the same target (game fish) 310 from two different ranges, with two different potential Doppler shifted echoes. Yet further, the towed sensor 382 is further away from the vessel 370 (in depth) than the wake and prop wash (which buoyantly moves upwards with time) 378, so the towed sensor 382 may be more immune to clutter echoes of the wake and prop wash 378.
The additional sound transducer sensor 382 may be implemented as any of a single transducer, an acoustic split-beam sensor, and an acoustic phased array, or any combination thereof. The same signal processing chain (of
The additional sound transducer sensor 382 of
In some embodiments, wires 366 may be comprised of one or more electrical conductors that may include but are not limited to including copper material. In some embodiments, wires 366 may be comprised of optical fibers. In some embodiments, wires 366 may be comprised of optical fibers and one or more electrical conductors. The boat electronics 368 may include one or more electrical-to-optical (EO) or optical-to-electrical (OE) converters as transmitters or receivers. Wires 366 may be used to implement a portion of or all of the signal flow shown herein in
The boat electronics 368 may transmit data or signals along the wires 366 to one or more devices, receive data or signals along the wires 366 from one or more devices, and provide power along the wires 366 to the one or more devices. The signals may include echo data time series. The one or more devices may include but are not limited to include one or more transducers 380 (sensor, source, or both sensor and source), additional sound sensors 382, cameras 330, and dredges 308. As such, the wires 366 may be unidirectional, bidirectional, or multiplexed with any of power, data, and fiber connections.
In addition to the dredge 308 being equipped with acoustic targets, the dredge 308 may also be equipped with one or more temperature and depth sensor(s) 332, and the data 362 sent back to the boat electronics 368 by wires 366. This may allow the boat electronics 368 to display both the dredge depth 306a and temperature to the user, as well as to speed-up the boat 370, or to slow down the boat 370, so that the slightly negatively buoyant dredge rises or sinks, thus performing depth-wise station keeping along a thermocline temperature defined by the user. These may be useful because game fish 310 often feed along certain thermocline regions, because smaller fish 390 congregate on them.
In some embodiments, methods or systems may add target depth estimation by the use of split aperture (e.g., split beam) techniques. The aft-looking phased array 380 may have beams 386 formed by a processor (located in the transducer 380 or electronics 368), and the two-way range may provide azimuth angle and range to isolated targets (e.g., an attacking game fish 310). In addition, target depth 306b may be estimated by phase methods using an array of receive elements segmented vertically. These elements could be part of the existing phased array 380 (also 230 of
In some embodiments, methods or systems may add a camera 330, either for natural light video or laser electro-optic (EO) illumination, or both, the camera 330 being added to the sound head (where the transducer 380 is located) or to the dredge 308 (a towed lure spread). The camera 330 may provide (e.g., display) live video if the targets 310 are close enough to be seen, and the camera 330 may be powered by energy from the boat 370, via cable 358, and the video data may be sent back to the boat 370 by wires 366.
Embodiments are capable of detecting, localizing and/or tracking dredges using acoustic transducers mounted near or to the stern of a boat. The acoustic array used for this is an N-channel phased array 330. It is oriented so that it can steer beams from port to aft to starboard (or the converse) by electronic means known in the art of beamforming, and that vertical steering (in depth) can be accomplished by interferometry from two or more vertically-spaced transducers as part of the array assembly. Phased array may also be used to perform 3D beamforming, an expensive method known in the art. Range 312 (of
Embodiments are capable of detecting, localizing and/or tracking dredges using ordinary high-Q transducers, however wideband or broadband transducers that use chirp and other broadband waveforms may have improved performance. Detecting, localizing and/or tracking may be performed with a single transducer assembly (with multiple elements for beamforming), or from a transducer system having both a wide-angle transmit transducer and a phased array receiver transducer. The transmit transducer can be mounted in the same package as the receiver array, but they also could be mounted in separate packages, which may cost more but there is a slight system performance advantage to doing so.
Transducers 380 are below the waterline when in use. Depending on the stern 374 of the boat 370, the transducers 380 may be mounted to the stern if they are far enough from the prop and exhaust wash 378, but the preferred embodiment is on a retractable linkage that allows deployment at a depth 306c lower than the one or more propellers or other propulsers. The retraction means may be pole-type, or multibar linkage, or any other robust system for electrically, manually, pneumatically or hydraulically raising and lowering the one or more transducers. The one or more transducers 380 may also have a controlled pitch adjustment at the end of the linkage for system fine depression and elevation tuning as a function of the vessel's trim and speed.
In some embodiments, the dredge 308 is deployed at a depth (or location) 306a below, astride, or both below and astride the vessel 370. In some embodiments, the transducer 380 is deployed at a depth (or location) 306c below, astride, or both below and astride the vessel 370. In some embodiments, the transducer 380 is deployed at a depth (or location) 306c below, astride, or both below and astride at least one of the prop wash and exhaust in the water 302, thereby improving acoustic visibility of clean water 302 aftward and improving system capability. In contrast, existing approaches have indiscriminant mounting to the transom 374 without regard for where the prop wash exhaust are, resulting in reduced system capability.
Some embodiments may retract the wet-end components (e.g., transducer or transducers 380, pole 388, arms, articulation means, and other wet-end components known to one skilled in the art) either upwards towards the surface, or upwards and completely out of the water 302, resulting in lower hydrodynamic drag on the wet-end components. In some embodiments, the wet-end components may be retracted while the vessel 370 is transiting to or from a fishing area. Some embodiments may include a corresponding pole 388 or articulation mechanism as part of a system.
The very dynamic wake and/or exhaust created by the boat 370 may be a challenge, and so are surface waves behind the boat 370, both of which may be remedied by the present disclosure. Bottom echoes may also be challenging if the water is shallow enough. But the present disclosure can overcome bottom echoes by using Doppler filtering, because the dredge 308 targets may have zero or near-zero Doppler with respect to the boat 370, and the wakes, exhaust, bottom and/or waves are almost entirely negatively Doppler-shifted, while the game fish 310 that are desired to be caught may be at zero Doppler while they are hunting and then positive Doppler shift when they attack the dredge 308.
In some embodiments, the boat 370 may include a display showing the dredge targets (a known number), the target depth(s), very little wake, very little exhaust plume, very little bottom echoes, few surface wave echoes, and when they arrive game fish 310 attacking the dredge 308. The display may include a sector image showing, for example, the 120° sector behind the boat 370, and out to a distance of ˜150 m, and from near horizontal to perhaps 45° downward.
Some embodiments may add acoustic enhancement targets onto the dredge 308 to improve their acoustic visibility, while also not interfering with the lures. The game fish 310 may be uncooperative but they are also very dynamic and have reasonable acoustic target strengths, so they can also be identified and imaged at the periphery of the sector-scene, as they move towards the dredge 308 which is closer to the center of the display.
In stark contrast to the present disclosure, at present there is no existing approach that provides real-time situational awareness of the fishing gear behind the boat, at ranges too long for optical methods (camera). Existing approaches have asserted that the boat wake may make situational awareness at ranges too long for optical methods unlikely to work from a boat-mounted sonar. However, successful experiments performed on some embodiments have shown that such methods do work (in accordance with the systems and methods of some embodiments herein) as demonstrated with data. Also in stark contrast to the present disclosure, existing approaches also do not use lure-type fishing dredges with sonar.
In addition, another novel aspect of the present disclosure is aft-looking imaging sonar. Existing approaches use downward-looking and forward-looking sonar imaging, but not aft-looking from the combined use of wideband sonar, phased array, vertical interferometry, and/or electro optic (EO) imaging.
Introduction
Some embodiments may include a system for the AFT acoustic detection, localization, tracking and classification of predatory marine game fish 310 (tuna, sailfish, billfish e.g.), as well as detection, localization, tracking of a towed lure spread (dredge), from a marine vessel (usually a boat). The system may use a combination of energy detection, Doppler detection and filtering (surface-, bottom-, and wake-turbulence clutter), and target TMA (Time Motion Analysis) to extract fish parameters (detection, location and depth, speed, direction vector, and aspect-corrected size estimate) and cueing of accessory narrow field-of-view optical (vision, lidar or very high frequency acoustic) imagers.
Sound attenuation varies with frequency: approximately f2 attenuation. The acoustic frequency for optimum system performance may be influenced by attenuation, but it also varies by the need for small acoustic wavelengths to obtain fine spatial resolution. These two factors are inversely related, so this becomes an engineering system tradeoff
Embodiments are capable of operating near 160 kHz for convenience because of commercially-available small circa 150 kHz linear 8-element phased transducer array usually used for swath sonar imaging that is small enough to be mounted on a pole from the transom 374 and aimed aft-wards and below the waterline. Embodiments are capable of using a commercial sounder (a combined amplifier, processor and display) with this transducer to obtain aft-looking sonar echoes. Such commercial systems are intended for downward and swath imaging during forward boat movement, within a typical angular sector of ±60° from nadir. Herein, nadir is defined as the direction pointing directly below a particular location. Some embodiments have instead rotated the transducer array so that it looks aft, with a wide port-aft-starboard field-of-view.
Some embodiments may include an electro-optical (EO) laser scanner range-finder. According to some embodiments, such an EO laser scanner may work better than a camera provided good optical clarity, and may allow acoustic-cueing and real-time optical display of fish species.
Some embodiments preferably use a field-of-view to ±45° from directly aft, because these are directions that are more aft than they are port or starboard. As configured by some commercial swath systems, and using the phased array transducer 380, some embodiments can obtain echoes beyond 300 m range, so a higher frequency may be used in a dredge fishing detection system because there is no need to look aft that far. A max range of approximately 100 m may be adequate, which means the frequency could be increased, or the power reduced (from 1 kW), or both. This means there a considerable increase in frequency could be made, so long as the power handling ability is acceptable.
Some embodiments may allow dual-band or tri-band frequency systems. According to some embodiments, the band around 150 kHz may be used to obtain coarse low-resolution at longer ranges, and higher resolution at the third harmonic band centered at 450 kHz for regions closer to the boat. Examples would be the dual-frequency and tri-frequency bar piezoelectric ceramics where the lowest-, mid- and highest-frequencies are respectively from the length-mode that couples into thickness motion, the width-mode that couples into thickness motion, and of course the thickness mode. Likewise, the fundamental radial mode for a disk piezoelectric ceramic couples into the thickness direction for a low frequency, as well as having an odd-harmonic series of thickness modes that are already aligned to radiate sound effectively. That also means that small segments of ceramics can be aligned into the footprint of a preferred shape to create the one or more beamwidths of choice for each vibration mode, thereby allowing the use of many small low-cost ceramic parts, in place of high-cost single bars or disks.
Dredges are commercially made and sold for sport fishing. These are umbrella-like spreads of boat-towed fishing lures 320 designed to mimic a school of bait fish 390. The dredges 308 do not have, however, any deliberately-affixed acoustic targets because they are not used in concert with a purpose-built aft-looking acoustic system. In some embodiments, by adding one or more acoustic reference targets 320 to the dredge, the dredge may be more easily detected and localized from an aft-looking sonar, and then seen on the sonar display. According to some embodiments, because these acoustic reference targets 320 are of known physical size, their acoustic target strength (TS), is precisely known a priori and used as an in-situ known reference with which the echo of a predatory game fish, that attacks the dredge lures 320, may be compared. Tracking and speed estimates, along with the aspect-dependent echo strength, allows for an estimate of the broadside acoustic target strength (TS) thereby estimating the maximum fish size and length.
According to some embodiments, the acoustic target(s) 320 may be made of differing sizes with, for example, large, medium and small using a sphere or spherical cap molded design with a surrounding hydrodynamic fairing. These strong artificial acoustic targets 320 can also be used as acoustic guide star, like the laser guide star used in adaptive optics, to help correct to sharpen acoustic images when used with phased array transducers and to correct for micro-multipath and the resulting phase aberrations that result.
According to some embodiments, game fish 310 may have acoustic target strengths, TSfish, that are largest at broadside, and are time-varying for approaching fish. Max Doppler roughly occurs when TS is frontal, and maximum TS when Doppler is near zero, and with a range of Doppler shifts and echo strengths during the complicated fish motion as it attacks the dredge 308. These can be used in a physics- and math-based model for the fish that can extract the most probable fish size and length.
Some embodiments may include size and frequency effects of the transducer 380: higher frequency provides narrower beam resolution; higher frequency also provides a larger frequency base for fish positive Doppler shift (up-Doppler) and fish Doppler bandwidth hence easier separation with down-Doppler clutter. Doppler shifts in the acoustic frequency occur because there is relative movement between the sonar on the moving boat 370, and the objects 320 the sound encounters.
The marine bottom, if close enough to have a measurable echo, may move away from the sonar so it has a down-Doppler shifted echo. The turbulent boat wake and prop wash 378 is a weak sound scatterer, but any echoes from it would be down-Doppler because they also move away from the boat 370. The dredge and dredge-mounted acoustic reference targets have close to, or identical to, zero-Doppler because they are held at a fixed distance from the boat during use. A game fish approaches the boat 370, initially from the sides or from aft 374, and eventually from aft 374 as they chase the dredge. So they might have an initial weak up-Doppler but will eventually have an up-Doppler echo. According to some embodiments, signal processing may be employed to sort out such issues. Such signal processing may include but is not limited to including Doppler filtering (FFT; filter into separate bands: down Doppler, zero Doppler, and up-Doppler; then IFFT) followed by range compression. In another embodiment, range compression for target detection may be accomplished in a parallel signal path than the Doppler filtering path.
There is a need to control the acoustic main and side lobes towards the surface and surface reverb. This is a matter of transducer and array system design, possibly using an asymmetric vertical beam pattern. In some embodiments, this allows a spatial reduction of clutter energy prior to Doppler spectral filtering. The vessel wake, and/or, the bubbly prop wash 378 from the boat 370, is the main source of acoustic clutter for an aft-looking system. In vessels used for fishing the boat size and boat speed are both usually small enough such that the acoustic transducer can send and receive acoustic waves beneath the wake and prop wash. At longer ranges from the boat, the prop wash will rise with the engine exhaust and that also helps allow the acoustic waves to pass beneath the wake and wash contrail. This allows acoustic visibility of the dredge lures, affixed dredge targets, and attacking game fish 310. Various means of affixing an aft-looking sonar are known in the prior art including transom mounting, stern scissors- and retraction-mounts, as well as hollow thru-hull fittings with retractable sensors 332. The acoustic sensors 332 may be monostatic (single transmit/receive) or bi- and multi-static (source and receiver(s) are separated). Source transmit may be all-at-once wide-angle illumination, and/or directed single narrow-angle beam. Receive is performed by a phased array of elements so that detection and tracking may be performed in 2D (range, azimuth), or in azimuth and elevation for a higher cost 3D system (range, azimuth, elevation).
According to some embodiments, in the up-Doppler data (which slightly overlaps zero Doppler) perform target tracking from ping-to-ping. Estimate fish trajectory, speed, body flexure (wiggle) rate (e.g., how fish 310 propel themselves), and body aspect versus time with respect to sonar. Using reference acoustic target echoes on dredge 308, estimate target strength (TS) of fish 310 versus time-varying body aspect so that broadside max fish TS and length may be estimated. Using very wideband up-Doppler echo data, perform range compression to extract fish cardinal anatomical features from principal echo envelope versus time. This may help species ID.
Biologic tissue is more non-linear than water, so nonlinear acoustic imaging can be useful in a marine environment. The method was pioneered in ultrasonic medical imaging in the 1990s but it relied on nonlinear path propagation. In marine acoustics the propagation path is still present, but the target is even more nonlinear than the water. This offers enhancements to the TS at a number of frequencies. In this case, time-varying broadband waveforms are used to reduce the likelihood that a fish echo may have a beam pattern null in the echo direction.
Some embodiments may use simultaneous (broadband) waveform transmit at frequencies f1 and f2 to exploit nonlinearity
Range Doppler Filtering:
According to some embodiments, and as illustrated collectively in
The resulting FFT data may generally fall into one of the following three regions, as illustrated in
1. Down Doppler clutter (
2. Zero Doppler (
3. Up Doppler (
In addition,
Range Doppler Filtering—Doppler Processing:
Doppler processing may be implemented using audio band hardware and/or signal processing. Some embodiments may implement Doppler processing using one or more of the approaches to follow. In the approaches to follow, the Doppler frequencies listed below are preferably after baseband into audio region.
1. Attacking Game Fish, also few, in discrete range bins, up Doppler:
For an attacking game fish, with V=+2.57 to 6 m/s (or larger), fDoppler shift=fo(1+V/ĉ)(1+V/ĉ)−fo=0 to +1200 Hz (or larger) (Doppler shift could be 0 Hz to 1200 Hz or higher depending on radial velocity of game fish), where V=separation_speed=|Vfish|−|Vdredge|=|Vfish|−|Vboat| because Vboat=Vdredge.
2. Gas bubbles and/or turbulence from prop wash and boat wake, and bottom echoes moving away from boat, occurs in many range bins, down Doppler:
For a gas bubble, the Doppler frequency shift is: fo(1−V/ĉ)(1−V/ĉ)−fo≈−2foV/ĉ=−682 Hz to −2300 Hz or larger Doppler shift is negative with forced prop convection. V=separation_speed=|Vboat|+|Vwake|.
Dredge targets are few, they occur in discrete range bins with very little change unless the dredge is moved; has approximately zero Doppler:
Zero Doppler because the distance to/from the dredge and boat is almost constant (i.e., no significant Doppler shift).
Next,
As illustrated in
As further illustrated in
Time Varied Gain=20 log10(voltage)+40 log10(R)+2 αR where voltage is measured by the beamformer, R is range, and a is the absorption coefficient of sound.
As illustrated in
As illustrated in
As further illustrated in
Next, one of three Doppler shift results, including but not limited to an Up Doppler shift 560, Zero Doppler shift 564, or Down Doppler shift 568 may be determined based upon the result 570 of Range Doppler Filtering. In addition, Up Doppler 560 is found from 570, and may use the Initial Fish TS estimate 524. Further, Zero Doppler 564 may also be determined from 570 and based upon a number, position, or size of artificial acoustic reference targets (also referred to as “target objects” herein) 580 that may be based upon computer control 536.
As illustrated in
As illustrated in
Reference Acoustic Targets:
As illustrated in
Some embodiments may employ one or more of the following features and/or considerations (and/or method steps and/or system components) in implementation of acoustic detection, localizing, tracking, and sizing of reference objects and/or target objects:
First, power amplifier behavior may be approximately known but not precisely (nominally to within 0.5 dB, or +/−5%). The amp may provide a powerful waveform to the sonar transducer array assembly. Transducer transmit response (TX) and receive response (RX) may also be approximately known, but may vary within as much as 3 dB for combined TX and RX values, especially from sample to sample. Careful calibration measurements can be made, but these may be costly and time consuming. These two things may place an uncertainty in the absolute acoustic echo level from a fish that can vary within 3-4 dB, assuming everything else is ideal and the fish is motionless.
Micro-multipath from the sonar, to the fish, and back can also cause weak fluctuations in the absolute acoustic echo level from 0.25 to 3 dB depending on water vorticity, unsteady water temperature, travel distance, and air bubbles. This is observed as very minor time-varying fading, so in the ocean it can be more of a problem. For these combined reasons, one or more reference acoustic targets (including but not limited to reference objects) may be affixed to the dredge.
The reference acoustic targets (including but not limited to reference objects) may be constructed of acoustic reflecting materials, such as air-filled plastics or metals, and of specific sizes so that they have a priori known acoustic targets strengths. The reference acoustic targets may be optionally coated for water intrusion resistance and drag reduction, and weighted to make them neutrally-buoyant when affixed to the dredge, and often disguised as lures.
According to some embodiments, for non-limiting example, an air-filled ping pong game ball may have a theoretical TS of −40 dB for α>>λ, where αis 19.5 mm radius, λ is the acoustic wavelength (λ=c/f), c is the sound speed and f is acoustic frequency. Spherical, partial-spherical, or hemispherical shapes may be well suited for use because the TS is approximately independent of the incident angle from the boat-mounted sonar.
An echo from the reference target has an echo voltage (EV) value, in dB re μPa, from the sonar equation:
EV=TVR+20 log10(V)−40 log10(R)−2αR+TSmeas+RVR
TVR and RVS may be approximately known because they are characteristics of the sonar transducer, and V is the drive voltage from the amplifier. One-way range R is known from the two-way time of flight At and the sound speed c, R=c*Δt/2. Spherical spreading occurs twice, at 20 log10 (R) for each of the outgoing and echo directions. Water temperature may be precisely measured, and the sound speed may be accurately calculated from it. The absorption coefficient a may be known from accurate math models for acoustic loss, because the acoustic frequency f may be known. EV may be measured by signal processing, after adjusting for any gains in the preamp.
Because EV may be now known, the measured target strength, i.e. TSmeas, may be evaluated by manipulation and substitutions into the sonar equation:
TSmeas=EV−TVR−RVR−20 log10(V)+40 log10(R)+2αR
Since TSknown may be available a priori, this may lead to a correction:
Correction_dB=TSknown−TSmeas
This correction may compensates for the combined system unknowns (transducer, amp, propagation) and may then be applied to the received time series, thereby providing an initial correction to any observed fish target strength, TSfish. This does not provide a complete correction to the TSfish because the aspect dependence of the one or more fish (one or more target objects) with respect to the sonar may not be performed. For that correction to be made, the fish (target objects) are preferably tracked over time, over a number of j pings in
Fish TS: Aspect Dependence
Acoustic echoes from fish may be complex, because the fish (target objects) may have many scattering materials (tissue, cartilage, air bladders, bones) and many more geometric shapes.
Fish also may change their shape as they propel themselves, so the acoustic scattering geometry may vary during motion. Finally the incident direction (azimuthal and depression/elevation angles) and the frequency of the sound may further complicate the echo creation.
For the most part, fish echoes are strongest from the side, broadside, or lateral directions and smallest from either the front (anterior) or the back (posterior) directions. Schematically, the fish nose 706 points at 0° and the tail 712 points at 180° in a dorsal-ventral midsagittal plane of a TS plot, as illustrated in
According to some embodiments, the reference “Modeling the detection range of fish by echolocating bottlenose dolphins and harbor porpoises,” J. Acoust. Soc. Am 121 (6), June 2007 (incorporated herein by reference in its entirety) provides additional examples of Aspect dependence, in which the max TS is shown as 0 dB relative in each polar plot.
The reference “Discriminating Chinook salmon by echolocating orca,” J. Acoust. Soc. Am 128 (4), 2225-2232 (2010) (incorporated herein by reference in its entirety) provides further background regarding corresponding echo waveforms and polargrams as a function of both frequency and angle.
In addition, according to some embodiments,
1. The max TS of small fish 390 is −40 dB or smaller. These fish are considered bait-size (or bite size) fish 390 and undetected unless in a school.
2. A 1 ft (0.3048 m) fish (−32 dB max TS, −42 to −47 dB frontal) may be at the edge of detection.
3. Large fish (predators) max TS to be −25 or larger.
4. So we need to detect −35 to −40 dB, or greater, looking aft from the boat for −20 to −25 dB game fish.
Client computers/devices 50 may be configured with a computing module (located at one or more of elements 50, 60, and/or 70). In some embodiments, a user may access the computing module executing on the server computers 60 from a user device, such a mobile device, a personal computer, or any computing device known to one skilled in the art without limitation. According to some embodiments, the client devices 50 and server computers 60 may be distributed across a computing module.
Server computers 60 may be configured as the computing modules which communicate with client devices 50 for providing access to (and/or accessing) databases that include data associated with target objects and/or reference objects. The server computers 60 may not be separate server computers but part of cloud network 70. In some embodiments, the server computer (e.g., computing module) may enable users to determine location, size, or number of physical objects (including but not limited to target objects and/or reference objects) by allowing access to data located on the client 50, server 60, or network 70 (e.g., global computer network). The client (configuration module) 50 may communicate data representing the physical objects back to and/or from the server (computing module) 60. In some embodiments, the client 50 may include client applications or components executing on the client 50 for determining location, size, or number of physical objects, and the client 50 may communicate corresponding data to the server (e.g., computing module) 60.
Some embodiments of the system 1000 may include a computer system for determining location, size, or number of physical objects. The system 1000 may include a plurality of processors 84. The system 1000 may also include a memory 90. The memory 90 may include: (i) computer code instructions stored thereon; and/or (ii) data representing location, size, or number of physical objects. The data may include segments including portions of the location, size, or number of physical objects. The memory 90 may be operatively coupled to the plurality of processors 84 such that, when executed by the plurality of processors 84, the computer code instructions may cause the computer system 1000 to implement a computing module (the computing module being located on, in, or implemented by any of elements 50, 60, 70 of
According to some embodiments,
In one embodiment, the processor routines 92 and data 94 are a computer program product (generally referenced 92), including a computer readable medium (e.g., a removable storage medium such as one or more DVD-ROM's, CD-ROM's, diskettes, tapes, etc.) that provides at least a portion of the software instructions for the present disclosure. The computer program product 92 can be installed by any suitable software installation procedure, as is well known in the art. In another embodiment, at least a portion of the software instructions may also be downloaded over a cable, communication and/or wireless connection. Other embodiments may include a computer program propagated signal product 107 (of
In alternate embodiments, the propagated signal is an analog carrier wave or digital signal carried on the propagated medium. For example, the propagated signal may be a digitized signal propagated over a global network (e.g., the Internet), a telecommunications network, or other network. In one embodiment, the propagated signal is a signal that is transmitted over the propagation medium over a period of time, such as the instructions for a software application sent in packets over a network over a period of milliseconds, seconds, minutes, or longer. In another embodiment, the computer readable medium of computer program product 92 is a propagation medium that the computer system 50 may receive and read, such as by receiving the propagation medium and identifying a propagated signal embodied in the propagation medium, as described above for computer program propagated signal product.
Generally speaking, the term “carrier medium” or transient carrier encompasses the foregoing transient signals, propagated signals, propagated medium, storage medium and the like.
Some embodiments are successfully tested and capable of various results. As such, some embodiments are capable of handling Background Acoustic Clutter from Boat Prop Wash using a transducer.
In some embodiments, the following are included: (1) Grayscale map at 4 knots (2) Vessel looking aft approximately 200 ft (61 m), (3) approximately 90° sector view, and (4) no dredge.
In some embodiments, the transducer is pointed aft using narrow vertical beam(8°) but sidelobes intercept engine prop wash, so acoustic scattering is most visible in an image center. Some embodiments provide a vertical beam coverage wide enough to see the dredge and attacking gamefish, but narrow enough to not see the prop wash or surface clutter echoes. In some embodiments, downward pitch angle helps limit prop wash echoes and surface clutter at the expense of dredge acoustic coverage.
In some embodiments, a low-sidelobe 18° vertical beamwidth transducer acoustic image may show reduced engine prop wash, so acoustic scattering may be weakly visible in an image center. Some embodiments enable excellent wide vertical coverage with minimal prop wash and surface clutter.
Some embodiments may include weak intermittent surface clutter.
In some embodiments, the following are included: (1) Grayscale map at 4 knots (2) Vessel looking aft approximately 200 ft (61 m), (3) approximately 90° sector view, and (4) dredge with acoustic targets.
In an embodiment, a low-sidelobe 18° vertical beamwidth transducer acoustic image shows persistent (from frame to frame) strong acoustic target within a dashed ellipse in a display. Some embodiments may include a photo inset: a pre-deployment dredge with lures and acoustic targets.
Embodiments or aspects thereof may be implemented in the form of hardware (including but not limited to hardware circuitry), firmware, or software. If implemented in software, the software may be stored on any non-transient computer readable medium that is configured to enable a processor to load the software or subsets of instructions thereof. The processor then executes the instructions and is configured to operate or cause an apparatus to operate in a manner as described herein.
Further, hardware, firmware, software, routines, or instructions may be described herein as performing certain actions and/or functions of the data processors. However, it should be appreciated that such descriptions contained herein are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc.
It should be understood that the flow diagrams, block diagrams, and network diagrams may include more or fewer elements, be arranged differently, or be represented differently. But it further should be understood that certain implementations may dictate the block and network diagrams and the number of block and network diagrams illustrating the execution of the embodiments be implemented in a particular way.
Accordingly, further embodiments may also be implemented in a variety of computer architectures, physical, virtual, cloud computers, and/or some combination thereof, and, thus, the data processors described herein are intended for purposes of illustration only and not as a limitation of the embodiments.
While this disclosure has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the disclosure encompassed by the appended claims.
This application claims the benefit of U.S. Provisional Application No. 62/569,343 filed on Oct. 6, 2017. The entire teachings of the above application are incorporated herein by reference.
Filing Document | Filing Date | Country | Kind |
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PCT/US2018/054406 | 10/4/2018 | WO | 00 |
Number | Date | Country | |
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62569343 | Oct 2017 | US |