1.
Remote sensing
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Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object and thus in contrast to on-site observation. It may be split into active remote sensing and passive remote sensing, passive sensors gather radiation that is emitted or reflected by the object or surrounding areas. Reflected sunlight is the most common source of radiation measured by passive sensors, examples of passive remote sensors include film photography, infrared, charge-coupled devices, and radiometers. Active collection, on the hand, emits energy in order to scan objects and areas whereupon a sensor then detects. RADAR and LiDAR are examples of remote sensing where the time delay between emission and return is measured, establishing the location, speed and direction of an object. Remote sensing makes it possible to data of dangerous or inaccessible areas. Remote sensing applications include monitoring deforestation in areas such as the Amazon Basin, glacial features in Arctic and Antarctic regions, military collection during the Cold War made use of stand-off collection of data about dangerous border areas. Remote sensing also replaces costly and slow data collection on the ground, the basis for multispectral collection and analysis is that of examined areas or objects that reflect or emit radiation that stand out from surrounding areas. For a summary of major remote sensing satellite systems see the overview table, conventional radar is mostly associated with aerial traffic control, early warning, and certain large scale meteorological data. Other types of active collection includes plasmas in the ionosphere, interferometric synthetic aperture radar is used to produce precise digital elevation models of large scale terrain. Laser and radar altimeters on satellites have provided a range of data. By measuring the bulges of water caused by gravity, they map features on the seafloor to a resolution of a mile or so, by measuring the height and wavelength of ocean waves, the altimeters measure wind speeds and direction, and surface ocean currents and directions. Ultrasound and radar tide gauges measure sea level, tides and wave direction in coastal, light detection and ranging is well known in examples of weapon ranging, laser illuminated homing of projectiles. Vegetation remote sensing is an application of LIDAR. Radiometers and photometers are the most common instrument in use, collecting reflected and emitted radiation in a range of frequencies. The most common are visible and infrared sensors, followed by microwave, gamma ray and rarely and they may also be used to detect the emission spectra of various chemicals, providing data on chemical concentrations in the atmosphere. Simultaneous multi-spectral platforms such as Landsat have been in use since the 1970s and these thematic mappers take images in multiple wavelengths of electro-magnetic radiation and are usually found on Earth observation satellites, including the Landsat program or the IKONOS satellite. Landsat images are used by agencies such as KYDOW to indicate water quality parameters including Secchi depth, chlorophyll a density
2.
Traffic enforcement camera
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It may be linked to an automated ticketing system. Vehicles owners are required by law to identify the driver of the vehicle. Some groups, such as the National Motorists Association in the USA, revenue-driven enforcement rather than the declared objectives. Other systems use a camera mounted on the bus, for example in London where they monitor Red routes on which stopping is not allowed for any purpose. Entry and Exit cameras determine the length of stay and provide alerts for unregistered or vehicles of concern via onscreen and this system was the first of several Sensor Dynamics based ANPR solutions. A red light camera is a camera that takes an image of a vehicle that goes through an intersection where the light is red. Speed enforcement cameras are used to monitor compliance with speed limits, other speed enforcement systems are also used which are not camera based. Fixed or mobile speed camera systems that measure the time taken by a vehicle to travel two or more fairly distant sites are called automatic number plate recognition cameras. These cameras time vehicles over a fixed distance, and then calculate the vehicles average speed for the journey. The name derives from the fact that the technology uses infrared cameras linked to a computer to read a vehicles registration number, in 2007, the Mountains Recreation and Conservation Authority, in California, installed the first stop sign cameras in the United States. The five cameras are located in parks such as Franklin Canyon Park. The operator, Redflex Traffic Systems Inc. is paid $20 per ticket, the fine listed on the citation is $100. In 2010, a class action lawsuit was filed against MRCA, automatic number plate recognition can be used for purposes unrelated to enforcement of traffic rules. In principle any agency or person with access to either from traffic cameras or cameras installed for other purposes can track the movement of vehicles for any purpose. In Australias SAFE-T-CAM system, ANPR technology is used to long distance truck drivers to detect avoidance of legally prescribed driver rest periods. In the UK an 80-year-old pensioner John Catt and his daughter Linda were stopped by City of London Police while driving in London and they had their vehicle searched under section 44 of the Terrorism Act 2000 and were threatened with arrest if they refused to answer questions. Critics point out that the Catts had been suspected of no crime, toll-booth cameras to identify vehicles proceeding through a toll booth without paying the toll Turn cameras at intersections where specific turns are prohibited on red. This type of camera is used in cities or heavy populated areas
3.
Speed limit
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Road speed limits are used in most countries to set the maximum speed at which road vehicles may legally travel on particular stretches of road. Speed limits may be variable and in some places speeds are unlimited, Speed limits are normally indicated on a traffic sign. Speed limits are set by the legislative bodies of nations or provincial governments. The first maximum speed limit was the 10 mph limit introduced in the United Kingdom in 1861, the highest posted speed limit in the world is 140 km/h, which applies to some roads in Poland and Bulgaria, similarly Texas posts 85 mph on one 40-mile long toll road. However, some roads have no speed limit for certain classes of vehicles, best known are Germanys less congested Autobahns, where automobile drivers have no mandated maximum speed. Measurements from the German state of Brandenburg in 2006 showed average speeds of 142 km/h on a 6-lane section of autobahn in free-flowing conditions, rural roads on the Isle of Man and the Indian states of Andhra Pradesh, Maharashtra, and Telangana, also lack speed limits. Speed limits are set to attempt to cap road traffic speed. It is often done with an intention to improve traffic safety. Speed limits may also be set in an attempt to reduce the impact of road traffic. Some cities have reduced limits to as little as 30 km/h for both safety and efficiency reasons, however, it has also been shown that in some circumstances changing a speed limit has little effect on the average speed of cars. In situations where the road speed is considered too high by governments. For some classes of vehicle, speed limiters may be mandated to enforce compliance, since their introduction, speed limits have been opposed by some motoring advocacy groups. The United Kingdom Stage Carriage Act 1832 first introduced the offense of endangering the safety of a passenger or person by furious driving. The Locomotives on Highways Act 1896, which raised the limit to 14 mph is celebrated to this day by the annual London to Brighton Veteran Car Run. The first person to be convicted of speeding is believed to be Walter Arnold of East Peckham, Kent and he was fined 1 shilling plus costs. In Australia, during the early 20th century, there were reported for furious driving offences. One conviction in 1905 cited furiously driving 20 mph when passing a tram traveling at half that speed. Most jurisdictions use the metric speed unit of kilometers per hour for speed limits, while some, primarily the United States, Australia followed the United Kingdom system before changing to the metric system in the 1970s
4.
Radar gun
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A radar speed gun is a device used to measure the speed of moving objects. A radar speed gun is a Doppler radar unit that may be hand-held, vehicle-mounted or static. The radar speed gun was invented by John L. Barker Sr. and Ben Midlock, originally, Automatic Signal was approached by Grumman Aircraft Corporation to solve the specific problem of terrestrial landing gear damage on the now-legendary PBY Catalina amphibious aircraft. Barker and Midlock cobbled a Doppler radar unit from coffee cans soldered shut to make microwave resonators, the unit was installed at the end of the runway, and aimed directly upward to measure the sink rate of landing PBYs. After the war, Barker and Midlock tested radar on the Merritt Parkway, in 1947, the system was tested by the Connecticut State Police in Glastonbury, Connecticut, initially for traffic surveys and issuing warnings to drivers for excessive speed. Starting in February 1949, the police began to issue speeding tickets based on the speed recorded by the radar device. In 1948, radar was used in Garden City, New York. Speed guns use Doppler radar to perform speed measurements, Radar speed guns, like other types of radar, consist of a radio transmitter and receiver. They send out a signal in a narrow beam, then receive the same signal back after it bounces off the target object. From that difference, the radar speed gun can calculate the speed of the object from which the waves have been bounced. After the returning waves are received, a signal with a equal to this difference is created by mixing the received radio signal with a little of the transmitted signal. Since this type of speed gun measures the difference in speed between a target and the gun itself, the gun must be stationary in order to give a correct reading. Instead of comparing the frequency of the signal reflected from the target with the transmitted signal, the frequency difference between these two signals gives the true speed of the target vehicle. Modern radar speed guns normally operate at X, K, Ka, Radar guns that operate using the X band frequency range are becoming less common because they produce a strong and easily detectable beam. Also, most automatic doors utilize radio waves in the X band range, as a result, K band and Ka band are most commonly used by police agencies. For these reasons, hand-held radar typically includes an on-off trigger, Radar detectors are illegal in some areas. Traffic radar comes in many models, hand-held units are mostly battery powered, and for the most part are used as stationary speed enforcement tools. Stationary radar can be mounted in vehicles and may have one or two antennae
5.
Lidar
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Lidar is a surveying method that measures distance to a target by illuminating that target with a laser light. The name lidar, sometimes considered an acronym of Light Detection And Ranging, was originally a portmanteau of light, the technology is also used for control and navigation for some autonomous cars. Lidar sometimes is called laser scanning and 3D scanning, with terrestrial, airborne and its first applications came in meteorology, where the National Center for Atmospheric Research used it to measure clouds. The general public aware of the accuracy and usefulness of lidar systems in 1971 during the Apollo 15 mission. Although some sources treat the word lidar as an acronym, the term originated as a portmanteau of light, the first published mention of lidar, in 1963, makes this clear, Eventually the laser may provide an extremely sensitive detector of particular wavelengths from distant objects. Meanwhile, it is being used to study the moon by lidar, the Oxford English Dictionary supports this etymology. Currently no consensus exists on capitalization, reflecting uncertainty about whether or not lidar is an acronym, various publications refer to lidar as LIDAR, LiDAR, LIDaR, or Lidar. Lidar uses ultraviolet, visible, or near infrared light to image objects and it can target a wide range of materials, including non-metallic objects, rocks, rain, chemical compounds, aerosols, clouds and even single molecules. A narrow laser-beam can map physical features with high resolutions, for example. Lidar has been used extensively for research and meteorology. Lidar instruments fitted to aircraft and satellites carry out surveying and mapping – a recent example being the U. S. Geological Survey Experimental Advanced Airborne Research Lidar, NASA has identified lidar as a key technology for enabling autonomous precision safe landing of future robotic and crewed lunar-landing vehicles. Wavelengths vary to suit the target, from about 10 micrometers to the UV, typically light is reflected via backscattering, as opposed to pure reflection one might find with a mirror. Different types of scattering are used for different lidar applications, most commonly Rayleigh scattering, Mie scattering, Raman scattering, based on different kinds of backscattering, the lidar can be accordingly called Rayleigh Lidar, Mie Lidar, Raman Lidar, Na/Fe/K Fluorescence Lidar, and so on. Suitable combinations of wavelengths can allow for remote mapping of atmospheric contents by identifying wavelength-dependent changes in the intensity of the returned signal, in general there are two kinds of lidar detection schemes, incoherent or direct energy detection and coherent detection. In both coherent and incoherent lidar, there are two types of models, micropulse lidar systems and high energy systems. Micropulse systems utilizing intermittent bursts of energy have developed as a result of the amount of computer power available combined with advances in laser technology. They use considerably less energy in the laser, typically on the order of one microjoule, there are several major components to a lidar system, Laser — 600–1000 nm lasers are most common for non-scientific applications. They are inexpensive, but since they can be focused and easily absorbed by the eye, eye-safety is often a requirement for most applications
6.
Doppler effect
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The Doppler effect is the change in frequency or wavelength of a wave for an observer moving relative to its source. It is named after the Austrian physicist Christian Doppler, who proposed it in 1842 in Prague, a common example of Doppler shift is the change of pitch heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer. Compared to the frequency, the received frequency is higher during the approach, identical at the instant of passing by. When the source of the waves is moving towards the observer, therefore, each wave takes slightly less time to reach the observer than the previous wave. Hence, the time between the arrival of successive wave crests at the observer is reduced, causing an increase in the frequency, while they are travelling, the distance between successive wave fronts is reduced, so the waves bunch together. The distance between wave fronts is then increased, so the waves spread out. For waves that propagate in a medium, such as sound waves, the total Doppler effect may therefore result from motion of the source, motion of the observer, or motion of the medium. Each of these effects is analyzed separately, for waves which do not require a medium, such as light or gravity in general relativity, only the relative difference in velocity between the observer and the source needs to be considered. Doppler first proposed this effect in 1842 in his treatise Über das farbige Licht der Doppelsterne und einiger anderer Gestirne des Himmels, the hypothesis was tested for sound waves by Buys Ballot in 1845. He confirmed that the pitch was higher than the emitted frequency when the sound source approached him. Hippolyte Fizeau discovered independently the same phenomenon on electromagnetic waves in 1848, in Britain, John Scott Russell made an experimental study of the Doppler effect. The frequency is decreased if either is moving away from the other, the above formula assumes that the source is either directly approaching or receding from the observer. If the source approaches the observer at an angle, the frequency that is first heard is higher than the objects emitted frequency. When the observer is close to the path of the object. When the observer is far from the path of the object, to understand what happens, consider the following analogy. Someone throws one ball every second at a man, assume that balls travel with constant velocity. If the thrower is stationary, the man will receive one every second. However, if the thrower is moving towards the man, he will receive balls more frequently because the balls will be spaced out
7.
Radar
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Radar is an object-detection system that uses radio waves to determine the range, angle, or velocity of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, Radio waves from the transmitter reflect off the object and return to the receiver, giving information about the objects location and speed. Radar was developed secretly for military use by several nations in the period before, the term RADAR was coined in 1940 by the United States Navy as an acronym for RAdio Detection And Ranging or RAdio Direction And Ranging. The term radar has since entered English and other languages as a common noun, high tech radar systems are associated with digital signal processing, machine learning and are capable of extracting useful information from very high noise levels. Other systems similar to make use of other parts of the electromagnetic spectrum. One example is lidar, which uses ultraviolet, visible, or near infrared light from lasers rather than radio waves, as early as 1886, German physicist Heinrich Hertz showed that radio waves could be reflected from solid objects. In 1895, Alexander Popov, an instructor at the Imperial Russian Navy school in Kronstadt. The next year, he added a spark-gap transmitter, in 1897, while testing this equipment for communicating between two ships in the Baltic Sea, he took note of an interference beat caused by the passage of a third vessel. In his report, Popov wrote that this phenomenon might be used for detecting objects, the German inventor Christian Hülsmeyer was the first to use radio waves to detect the presence of distant metallic objects. In 1904, he demonstrated the feasibility of detecting a ship in dense fog and he obtained a patent for his detection device in April 1904 and later a patent for a related amendment for estimating the distance to the ship. He also got a British patent on September 23,1904 for a radar system. It operated on a 50 cm wavelength and the radar signal was created via a spark-gap. In 1915, Robert Watson-Watt used radio technology to advance warning to airmen. Watson-Watt became an expert on the use of direction finding as part of his lightning experiments. As part of ongoing experiments, he asked the new boy, Arnold Frederic Wilkins, Wilkins made an extensive study of available units before selecting a receiver model from the General Post Office. Its instruction manual noted that there was fading when aircraft flew by, in 1922, A. Hoyt Taylor and Leo C. Taylor submitted a report, suggesting that this might be used to detect the presence of ships in low visibility, eight years later, Lawrence A. Australia, Canada, New Zealand, and South Africa followed prewar Great Britain, and Hungary had similar developments during the war. Hugon, began developing a radio apparatus, a part of which was installed on the liner Normandie in 1935
8.
Automatic number-plate recognition
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Automatic number plate recognition is a technology that uses optical character recognition on images to read vehicle registration plates. It can use existing closed-circuit television, road-rule enforcement cameras, or cameras specifically designed for the task, ANPR is used by police forces around the world for law enforcement purposes, including to check if a vehicle is registered or licensed. It is also used for toll collection on pay-per-use roads. Automatic number plate recognition can be used to store the images captured by the cameras as well as the text from the license plate, Systems commonly use infrared lighting to allow the camera to take the picture at any time of the day. ANPR technology must take into account plate variations from place to place, concerns about these systems have centered on privacy fears of government tracking citizens movements, misidentification, high error rates, and increased government spending. Critics have described it as a form of mass surveillance, prototype systems were working by 1979, and contracts were awarded to produce industrial systems, first at EMI Electronics, and then at Computer Recognition Systems in Wokingham, UK. Early trial systems were deployed on the A1 road and at the Dartford Tunnel, the first arrest through detection of a stolen car was made in 1981. However, ANPR did not become widely used until new developments in cheaper and easier to use software were pioneered during the 1990s, the collection of ANPR data for future use was documented in the early 2000s. The software aspect of the runs on standard home computer hardware. When done at the site, the information captured of the plate alphanumeric, date-time, lane identification. This information can easily be transmitted to a computer for further processing if necessary. In the other arrangement, there are large numbers of PCs used in a server farm to handle high workloads. Often in such systems, there is a requirement to forward images to the server. ANPR uses optical character recognition on images taken by cameras, some license plate arrangements use variations in font sizes and positioning—ANPR systems must be able to cope with such differences in order to be truly effective. More complicated systems can cope with international variants, though many programs are tailored to each country. The cameras used can be existing road-rule enforcement or closed-circuit television cameras, as well as mobile units, some systems use infrared cameras to take a clearer image of the plates. Further scaled-down components at more cost-effective price points led to a number of deployments by law enforcement agencies around the world. Despite their effectiveness, there are noteworthy challenges related with mobile ANPRs, one of the biggest is that the processor and the cameras must work fast enough to accommodate relative speeds of more than 100 mph, a likely scenario in the case of oncoming traffic
9.
Stereoscopy
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Stereoscopy is a technique for creating or enhancing the illusion of depth in an image by means of stereopsis for binocular vision. The word stereoscopy derives from Greek στερεός, meaning firm, solid, any stereoscopic image is called a stereogram. Originally, stereogram referred to a pair of images which could be viewed using a stereoscope. Most stereoscopic methods present two offset images separately to the left and right eye of the viewer and these two-dimensional images are then combined in the brain to give the perception of 3D depth. Stereoscopy creates the illusion of depth from given two-dimensional images. One of the functions that occur within the brain as it interprets what the eyes see is assessing the relative distances of objects from the viewer, the two images are then combined in the brain to give the perception of depth. Although the term 3D is ubiquitously used, the presentation of dual 2D images is distinctly different from displaying an image in three full dimensions. The most notable difference is that, in the case of 3D displays, holographic displays and volumetric display do not have this limitation. Just as it is not possible to recreate a full 3-dimensional sound field with just two speakers, it is an overstatement to call dual 2D images 3D. The accurate term stereoscopic is more cumbersome than the common misnomer 3D, although most stereoscopic displays do not qualify as real 3D display, all real 3D displays are also stereoscopic displays because they meet the lower criteria also. Most 3D displays use this method to convey images. It was first invented by Sir Charles Wheatstone in 1838, but if it be required to obtain the most faithful resemblances of real objects, shadowing and colouring may properly be employed to heighten the effects. Flowers, crystals, busts, vases, instruments of various kinds, Stereoscopy is used in photogrammetry and also for entertainment through the production of stereograms. Stereoscopy is useful in viewing images rendered from large data sets such as are produced by experimental data. Modern industrial three-dimensional photography may use 3D scanners to detect and record three-dimensional information, the three-dimensional depth information can be reconstructed from two images using a computer by correlating the pixels in the left and right images. Solving the Correspondence problem in the field of Computer Vision aims to create meaningful depth information from two images, anatomically, there are 3 levels of binocular vision required to view stereo images, Simultaneous perception Fusion Stereopsis These functions develop in early childhood. Some people who have strabismus disrupt the development of stereopsis, however orthoptics treatment can be used to improve binocular vision, a persons stereoacuity determines the minimum image disparity they can perceive as depth. It is believed that approximately 12% of people are unable to properly see 3D images, according to another experiment up to 30% of people have very weak stereoscopic vision preventing them from depth perception based on stereo disparity
