The Underwater Detecting Target Computer Science Essay

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This paper is aimed to underwater detecting target by using the application of sonar. Nowadays, the used of sonar more widely applied as example in order to detect, recognize and relocation of lost underwater target, to simulate the system ( detect noise).......

Actually, sonar system is use to obtained information about underwater targets and events by transmitting sound wave and observing the return echoes. Means that sonar detection is based on the propagation of wave between the target and detector. The more detail about this research will be discuss in literature review summary.

SONAR (sound navigation and ranging) systems have many similarities to RADAR and electro-optical systems. Again, detection is based on the propagation of waves between the target and detector. There are active sonar systems, where the wave propagates from the transmitter to the target and back to the receiver, analogous to pulse-echo radar. There are also passive sonar systems, where the target is the source of the energy which propagates to the receiver, analogous to passive infrared detection. Therefore, a great deal of what has been discussed about these systems will also apply to sonar. Sonar, however, differs fundamentally from radar and electro-optics because the energy is transferred by acoustics waves propagating in water. So we first begin by discussing the characteristics of acoustic waves.

Besides that, a sonar system used for obtaining information about underwater objects and events by transmitting sound waves and observing the returned echoes. However, the human ear has a restricted range of perception of sound, limited approximately to frequencies between 16 and 20 000 Hertz (cycles per second, abbreviated Hz). Sonar systems used in fisheries work produce ultrasounds, i.e. sounds with a frequency usually ranging from 20 000 to 500 000 Hz (i.e. 20 to 500 kHz) which are not detectable by the human ear. An apparatus used for the detection and investigation of underwater targets by means of transmitted sounds and returned echoes is called an active sonar system or simply a sonar system.

- a system that transmits vertically is called an "echosounder" (Figure la)

- a system that transmits horizontally is called a "sonar" (Figure 1b)

The functioning of both kinds of apparatus is the sane. Therefore When discussing the basic theory of acoustics the functioning of acoustic equipment in general we will use the term "sonar system", and when discussing the practical use of a particular kind of equipment we will use one of the customary names, for example "echosounder" or "sonar".

The detection, classification and localisation performance of sonar depends on the environment and the receiving equipment, as well as the transmitting equipment in active sonar or the target radiated noise in a passive sonar. Active sonar uses a sound transmitter and a receiver. When the two are in the same place it is monostatic operation. When the transmitter and receiver are separated it is bistatic operation. When more transmitters (or more receivers) are used, again spatially separated, it is multistatic operation. Most sonars are used monostatically with the same array often being used for transmission and reception. Active sonobuoy fields may be operated multistatically.

Compared to Passive sonar listens without transmitting. It is often employed in military settings, although it is also used in science applications, for example in detecting fish for presence/absence studies in various aquatic environments - see also passive acoustics and passive radar. In the very broadest usage, this term can encompass virtually any analytical technique involving remotely generated sound, though it is usually restricted to techniques applied in an aquatic environment.


According to the reference we get about the history of Sonar by Mary Bellis, we have found that sonar is a system that uses to transmitted and reflected underwater objects or measure the distances underwater. It has been used for submarine and mine detection, depth detection, commercial fishing, diving safety and communication at sea. The Sonar device will send out a subsurface sound wave and then listens for returning echoes, the sound data is relayed to the human operators by a loudspeaker or by being displayed on a monitor.

Lewis Nixon invented the very first Sonar type listening device in 1906, as a way of detecting icebergs. Interest in Sonar was increased during World War I when there was a need to be able to detect submarines. The first Sonar devices were passive listening devices-no signals were sent out. By 1918, both Britain and the U.S. had built active systems, in active Sonar signals are both sent out and then received back. Acoustic communication systems are Sonar devices where there is both a sound wave projector and receiver on both sides of the signal path. The invention of the acoustic transducer and efficient acoustic projectors made more advanced forms of Sonar possible.

The word Sonar is an American term first used in World War II, it is an acronym for SOund, NAvigation and Ranging. The British also call Sonar, ASDICS, which stands for Anti-Submarine Detection Investigation Committee. Later developments of Sonar included the echo sounder, or depth detector, rapid-scanning Sonar, side-scan Sonar and WPESS (within-pulseectronic-sector-scanning) Sonar.

Sonar Image (Underwater Detecting Target and Recognition) by Norfarahana Binti Mat Jali

The first journal is a review of 3D-sonar image formatting and shape recognition techniques which are aimed to carry out the actual image formation approach by exploiting each beam signal (reduce the destructive noise influence due to environment impacts). This technique includes computationally efficiency, robust against noise and allows the application of 2D image processing.

3D-sonar use the simulation of high resolution in the underwater to simulate the scenes, object shapes and AUV movements as well as wave propagation and ambient noise. However, it still under consideration of single-ping and linear movement. For measurement simulation, it performs due to the beam former angular resolution and coverage and the result means the geometry target will be modelled as spherical shape.

For image formation, interpolation of a couple signals will be considered depending on its distance to the grid point. The developed underwater sonar performance simulation

techniques relative fast sonar performance predictions and future system specifications

are required.

For the second journal, its more concern of detect the target by multiple disparate sonar platform. This techniques involve the steps of detect, isolate and represent information among the multiple data then extract the mapping vector and correlation sum from the data sample.

This technique begin with a sonar will be place in the area target in order to get the sonar imagery with fusion across multiple algorithms. Then one type of filter will be applied to the three different sonar images which varying in frequency and bandwidth. For the final state, the decision of individual detector and classifier are fused by using an optimal set with a nonlinear log-likelihood test.

By using this method, it will allow to do the simulation among two sonar images in order to get the real detection target consider to multi-sonar will lead to the higher level coherence.

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The journal "Extraction and organization of metadata feature for underwater target recognition by sonar echoes" is discuss about the feature extraction method that used to recognize the target in the underwater world automatically. By this method, it will increase the rate of recognizing.

In this journal, a model of 2-dimensional metadata was designed which is consists of two elements where consists the temporal and frequency feature. Metadata actually is a descriptive data of the data and composed in two parts. After the basic signal was analysed, the features will be available. When the higher dimensions obtained, it will give the bad system performance.

The high recognized rate can be achieve by put the temporal and the frequency feature into account synthetically. After calculation and comparison, in the temporal and frequency domain, the audio fingerprint is improved and used in the extraction of the sonar echo simultaneously. According to Dalian, a model of 2-dimensional metadata can be defined as:

{Sonar fingerprint = audio fingerprint, zero cross rate (ZCR)}

The journal " False Alarm Reduction by LS-SVM for Manmade Object Detection from Sidescan Sonar Images, is discuss about the automatic manmade object detection from sidescan image which is important for automatic mine countermeasure. In purpose to make a high detection rate, the pattern of the recognition technique of support vector machines (SVM) is used. The advantages of SVM are:

Reduce the false detection

Have open stuctures

Can adjust the parameters

According to Ning Ma and Chin Swee Chia, in order to find the high detection rate, the 2 features are suggested. They are the shadow and highlight matching and the other is the intensity difference between the highlight and its surroundings.

By applying the LS-SVM, the false detection reduction is achieved around 50% and 80% of the correct detections can be maintain.


Sonar is the electronic system that can be categorized into three parts: the transducer array, the signal gathering and processing system and the display control system. The system need a large acoustic array with hundreds of sensors. Then its develops with a trend of modularization, standardization and serialization. The structure of sonar gathering and processing system can be mention by AD module and DSP module. The data will be flow from AD module to DSP module. The data structure of sonar gathering and processing system are combined together with P4 computer main board, primary AD board, Slave AD board, DA board, DSP board and communication board. Besides that sonar systems can provide massive power at modest cost. This system also provide instantaneous signal that have a dynamic range around 40-70 dB. However the other technology like BiCMOS provide the analogue/digital circuits with overall dynamic ranges up to 100 dB. But it is not fully developed because the present of this technology is expensive. However this system face some problems such as the design of the anti-alias filters to band limit the hydrophone signals before sampling, problem occur in the other pre-digitization circuits due to maintain the signal-to-noise ratio. To maintain a high performance data acquisition system for large aperture sonar there are some potential solutions that can be made. Some of the problems are transducer arrays are multi-channel sensors, rather than the one or two signal channels processed in most other applications, sonar bandwidths are low, signal dynamic range can be high, channel-to-channel gain and phase matching must be good, power dissipation needs to be minimized and size and cost are critical due to mechanical limitations and the number of channels in large aperture systems. Ideally one way to improve this system is by trade some analogue circuit complexity for an increase in the digital signal processing load. On the other hand, the sigma-delta conversion can be used by converting the circuits that can be designed without the need of complicated sample-and-hold circuits and anti-aliasing filters. However this advantages is complex, compact and low power implementation. For integrating a complete data acquisition systems the local voltage regulators, the hydrophone pre-amplifier, a low order anti-alias filter and circuits to serialize the converter output and to multiplex it onto a common highway must be combined and include together.(adapted from T. E. Curtis and A.B. Webb, Admiralty Research Establishment, Portland and Weimin Hou; Qingshan Tang; and Ruimei Zhao, Hebei University of Science and Technology, Shijiazhuang, 050018, China and Institute of Acoustics, Chinese Academy of Sciences, Beijing 100080, China).


With the increasing deployment of Autonomous Underwater Vehicles for mine countermeasures applications, the accurate detection and identification of underwater targets continues as a major issue. These systems can be highly dependent on the similarity of the test data to the training data, which includes the effect of the background region on which the target was located. Research carried out in developing mine-countermeasures MCM tools is generally split into Computer Aided Detection (CAD) to detect all possible mine-like objects, and Computer Aided Classification (CAC) models to classify whether the detected object is a mine or not. Typical sidescan systems used for mine countermeasures applications can provide a resolution of between 3cm and 10cm depending on operating range and frequency. New very high frequency systems, such as the Marine-Sonics 2.4MHz system offers resolution of lcm but is limited to operating ranges of less than about 6m.

False Alarm Reduction by LS-SVM for Manmade Object Detection from Sidescan Sonar Images

For automatic mine countermeasure the automatic manmade object detection from sidescan sonar image is a key for development of autonomous underwater vehicles. If the mine countermeasure system can find the target and destroy it without operator interfering a high detection rate and low false alarm rate are required. In our previous work, an algorithm for manmade object detection has been developed for after mission processing. The false alarm rate is more than 50%, which is too high for automatic mine countermeasure for to maintain a high detection rate for operator to further decision. In this work, to reduce false detections in our previous work we propose to use the pattern recognition technique of support vector machines (SVM) because of its open structure. To achieve the requirement of maintaining high detection rate it is possible to adjust the parameters. Of the correction of detections and the false detections and proposed to use 2 features to classify the false detection and correct detection. More than 50% of false detections have been reduced after applying the SVM, and above 80% correct detections are maintained.

Development of Underwater Security Sonar System

The underwater security sonar system are developed to guard oil plants, harbour, power plants, and LNG/Oil tankers for against underwater terror divers like attacking terrorist also for detected smuggling activities. Wharf security system are designed for detected activities underwater. It is to developing underwater acoustic surveillance system with sensor and integrated the cameras surveillance system can make this so perfect. Three type of intelligent acoustic scanning sonar systems capable of horizontally detecting and tracking targets in a far field are developed in three years and also compose two types of acoustic video cameras to see target as a high-resolution image with sector scanning sonar. Surveillance software and internet security communication for remote operation also developed and improved to control the underwater security sonar system. The performance when testing are great because the different of image of driving suit, shape boat, and fishing line can archived and observed. The software is uses as intelligently extract and locate suspected objects. The acoustic video camera is desired to improve the performance and resolution. It is necessary to improve the wharf surveillance system and to integrate the sensors.

Devising an Affordable Sonar System for Underwater 3-D Vision

The underwater optical vision is fine resolution for image but the range is limited than that acoustic sensor, but no 3-D. The design and evaluate of a 3-D acoustic image system are propose based on array planar of sensor. To design the 3-D imaging system, the real-time functioning and high resolution are essential but it's make the sonar system expensive and difficult because acoustic imaging has been limited. The a periodic sparse array are synthesized using stochastic near based on the simulated annealing algorithm and also compose more than 600 transducers. From two specific system configuration, which bandwidth of the transmitted and vary carrier frequency to generate images of good quality. For lower frequency, its make bigger range and field of view can do for surveying and object detection task. For higher frequency, is a better resolution.


The journal discuss about the "Simulation Technique of Radiated Noise from Underwater Target and Its Implementation of Simulator". The simulation of radiated noise is the key technique of testing passive sonar system and acoustical decoy. The radiated noise is composed of the machinery induced noise, propeller induced noise and hydrodynamic noise. The machinery induced noise is the radiated noise from various machinery vibration through hull when sailing. The propeller noise is the radiated noise from propeller that consist of the cavitation noise and blade rate noise. The hydrodynamic noise is formed the fluctuant seawater flow by the hull. The typical modelling method for the radiated noise mostly uses the line spectrum adds to the continuous spectrum. These modelling method is divided into four method which are, model and simulation of line spectrum, model and simulation of continuous spectrum, model of modulation envelope and the last is simulation of radiated noise.

The second journal is about "The simulation of short distance through signature multi-radiated sources of a ship". The ship-radiated noise at short distance is adopted to approach the continuous spectrum. The ship-radiated noise is an important characteristic to actualize the target detection, passive location and recognization. The ship-radiated can be use for long distance and short distance detection. For this section, it focus on short-distance detection. It is simulated based on the reconstruction of the ship-radiated noise and the simulating results are analyzed in the time and frequency domain. There are two types of simulation, the first simulation is for the continuos noise process and the second simulation is through signature of the ship-radiated noise. The ship-radiated noise arise from the source in every section of a ship, causes the noise produced and radiated by different component are distinct in frequency and time to reach the peak in diverse.

As the conclusion, the simulation model is important to produce the necessary data which approach the main characteristic of actual testing ship-radiated noise. From the simulation model, the techniques of detection and recognization can be study.



The "sonar" term is the means of microwave communication. The sonar system is used to detect and know the base of sea. Besides, it is used to find the obstacle between the way of traveling the submarine. Through this, it will avoid the accident in the sea and thus, this system is of great use of navigation purpose.

Sonar will be operates using sound wave and not by radio wave to detect the underwater objects. This is because, sound waves will be better in the application of radio waves underwater due to the loss of too much energy when they propagate in water.

Today, there are a lot of application of sonar in our lives, including determining the depth of the water, fishing, seabed mapping, and a variety of positions such things as pipelines, wellheads and shipwrecks. Sonar is also can be used to detemined the characteristics of the seabed sediment.

Sonar system is devided into two categories which are passive and active sonar. Passive sonar is the simplest category that consists of systems which is essentially do nothing but only listen for sound vibration in the water. In passive sonar systems target can be determined also from the direction in which the sound wave is detected, but detection coverage is much more difficult.

On the other hand, active sonar is more complicated and involve the projection of short pulses of sound that propagate through the water in a narrow beam at about 1500 m/s. The pulses are then reflected off the target may be on the beams.

In active sonar, the first rays of echolocation sent by electroacoustic tranducer that changes the signal power from a given period and the frequency of the voice signal transmitting into the water.