Fox

The fox is an especially popular animal in the Furry Fandom.
. The words "fox" or "foxy" have become synonymous slang in Western society for an individual (most often female) with sex appeal. China and France are also developing other satellite navigation systems. In Japanese folklore, the fox-like kitsune is a powerful animal spirit (Yōkai) that is highly mischievous and cunning. The European Union is developing Galileo as an alternative to GPS, planned to be in operation by 2010. In The Little Prince a fox indicates the true value of things like friendship. There are plans to restore GLONASS to full operation by 2008.

Some well-known stories involving foxes are found in Aesop's fables; another is the medieval story of Reynard. Russia operates an independent system called GLONASS (global navigation system), although with only twelve active satellites as of 2004, the system is of limited usefulness. In many cultures, the fox is a familiar animal of folklore, a symbol of cunning and trickery. There were also incidents of unintentional jamming, traced back to malfunctioning TV antenna preamplifiers. Stone carvings representing foxes have been found in the early settlement of Göbekli Tepe in eastern Turkey. According to the reference below, "IFR pilots should have a fallback plan in case of a GPS malfunction". The first example of the introduction of the fox into a new habitat by humans seems to be Neolithic Cyprus. And there has been at least one well-documented case of unintentional jamming; if similar, but stronger, signals were generated on purpose, they could interfere with aviation GPS receivers at a range of 50 km.

Historians believe foxes were being imported into non-native environments long before the colonial era. A detailed description of how to build a GPS jammer was posted on a hackers' site by an anonymous author. They have been successfully employed to control pests on fruit farms, leaving the fruit intact.[1]. Air Force conducted GPS jamming exercises in 2003. Foxes can be used for helpful environmental purposes as well. The U.S. On the other hand, many fox species are endangered. In either case, the jammers are attractive targets for anti-radiation missiles.

In some countries, such as Australia, with no strong competitors, imported foxes quickly devastate native wildlife and become a serious invasive pest. Some officials believe that jammers could be used to attract the precision-guided munitions towards noncombatant infrastructure, other officials believe that the jammers are completely ineffective. The former is used by foxes communicating over long distances, the latter in close quarters. invasion of Afghanistan. Fox noises can be divided, with a few exceptions, into two different groups: contact sounds and interaction sounds. government believes that such jammers were used occasionally during the U.S. These sounds grade into one another and span five octaves; each fox has its own characteristically individual voice. The U.S.

Fox families, however, keep in contact with a wide array of different sounds. GPS jammers are available, from Russia, and are about the size of a cigarette box. Foxes do not come together in chorus like wolves or coyotes do. A large part of modern munitions, the so-called "smart bombs" or precision-guided munitions, use GPS. Foxes include members of the following genera:. The increased accuracy comes mostly from being able to use both the L1 and L2 frequencies and thus better compensate for the varying signal delay in the ionosphere (see above). Foxes also gather a wide variety of other foods ranging from grasshoppers to fruit and berries. Military (and selected civilian) users still enjoy some technical advantages which can give quicker satellite lock and increased accuracy.

Using a pouncing technique practiced from an early age, they are usually able to kill their prey quickly. Authorized military units are still able to decrypt the corrected signals using a tamper-resistant hardware module called an SAASM, Selective Availability / Anti-Spoofing Module. They are solitary, opportunistic feeders that hunt live prey (especially rodents). The original SA system could only limit the accuracy of GPS signals world-wide, or not at all. Unlike many canids, foxes are not pack animals. The US military maintains the ability to use a more advanced version of Selective Availability, called "Selective Deniability", to reduce the accuracy of civilian GPS units in a specific area without affecting the rest of the world. For example, the Desert Fox has large ears and short fur, whereas the Arctic Fox has small ears and thick, insulating fur. [9].

Other physical characteristics vary according to their habitat. The military resisted for most of the 1990s, but SA was eventually turned off in 2000 following an announcement by then US President Bill Clinton, allowing all users to enjoy nearly the same level of access. Recognizable characteristics also include pointed muzzles and bushy tails. This would save the FAA millions of dollars every year in maintenance of their own, less accurate, radio navigation systems. With most species roughly the size of a domestic cat, foxes are smaller than other members of the family Canidae, such as wolves, jackals, and domestic dogs. In the 1990s the FAA started pressuring the military to turn off SA permanently. . During the Gulf War, the shortage of military GPS units and the wide availability of civilian ones among personnel resulted in disabling the Selective Availability.

A group of foxes is a skulk. In order to improve the usefulness of GPS for civilian navigation, Differential GPS was used by many civilian GPS receivers to greatly improve accuracy. Male foxes are known as dogs, tods or reynard, females are referred to as vixens, and their young are called kits or cubs, as well as pups. The inaccuracy of the civilian signal was deliberately encoded so as not to change very quickly, for instance the entire eastern US area might read 30 m off, but 30 m off everywhere and in the same direction. Fox terminology is different from that used for most canids. SA typically added signal errors of up to about 10 m horizontally and 30 m vertically. The presence of foxes all over the globe has led to their appearance in the popular culture and folklore of many nations, tribes, and other cultural groups. Additional accuracy was available in the signal, but in an encrypted form that was only available to the United States military, its allies and a few others, mostly government users.

The animal most commonly called a fox in the Western world is the Red Fox (Vulpes vulpes), although different species of foxes can be found on almost every continent. When it was first deployed, GPS included a feature called Selective Availability (or SA) that introduced intentional errors of up to a hundred meters into the publicly available navigation signals, making it difficult to use for guiding long range missiles to precise targets. A fox is a member of any of 27 species of small omnivorous canids. The accuracy of GPS can be improved in a number of ways:. Fuse the Fusion Radio fox. The citation accompanying the presentation of the trophy honors the GPS Team "for the most significant development for safe and efficient navigation and surveillance of air and spacecraft since the introduction of radio navigation 50 years ago.". Phil Coates. Air Force, the Aerospace Corporation, Rockwell International Corporation, and IBM Federal Systems Company.

Fox McCloud from the Star Fox series of video games. This team consists of researchers from the Naval Research Laboratory, the U.S. Fox and his mate Vixen led The Animals of Farthing Wood. Collier Trophy, the most prestigious aviation award in the United States. Miles "Tails" Prower, from Sonic the Hedgehog. On February 10, 1993, the National Aeronautic Association selected the Global Positioning System Team as winners of the 1992 Robert J. Basil Brush, British television personality. Two GPS developers have received the National Academy of Engineering Charles Stark Draper prize year 2003:.

Vulpes (the ten species of "true" foxes, including the Red Fox (vulpis vulpis). Bartolomé Coll has recently developed the basic notions necessary for a fully relativistic theory of Positioning Systems [7]. Urocyon (Gray Fox and Island Fox). Whether relativity must be considered as a mere correction to a Newtonian GPS theory, or, rather, as the necessary foundation of a cleaner (and more fundamental) GPS theory, is currently under debate. Pseudalopex (four South American species, including the Culpeo). Neil Ashby presented a good account of how these relativistic corrections are applied, why, and their orders of magnitude, in Physics Today (May 2002) [6]. Otocyon (Bat-eared Fox). This offset is a practical demonstration of the theory of relativity in a real-world system; it is exactly that predicted by the theory, within the limits of accuracy of measurement.

Lycalopex (Hoary Fox). This amounts to a discrepancy of around 38 microseconds per day, which is corrected by electronics on each satellite. Fennecus (Fennec, or Desert Fox). The clocks on the satellites are also affected by both special and general relativity, which causes them to run at a slightly faster rate than do clocks on the Earth's surface. Dusicyon (Falkland Island Fox). Several frequencies make up the GPS electromagnetic spectrum:. Cerdocyon (Crab-eating Fox). Shorter multipath signals from ground reflections can often be very close to the direct signals, and can greatly reduce precision.

Alopex (Arctic Fox). For shorter delay multipath signals that result from reflections from the ground, special antenna features may be used such as a ground plane, or a choke ring antenna. A variety of receiver techniques, most notably Narrow Correlator spacing, have been developed to mitigate multipath errors. For long delay multipath signals, the receiver itself can filter the signals out. GPS signals can also be affected by multipath reflections of the radio signals off the ground and/or surrounding structures (buildings, canyon walls, etc).

Newer GPS receivers can compare the phase difference between the L1 and L2 frequencies to actually measure the atmospheric effects on the signals and apply precise corrections.^{[citation needed]}. Because ionospheric delay affects the speed of radio waves differently based on their frequencies, a second frequency band was added to help eliminate this type of error. Once the receiver's rough location is known, an internal mathematical model can be used to estimate and correct for the error. The effect is minimized when the satellite is directly overhead and becomes greater toward the horizon, as the satellite signals must travel through the greater "thickness" of the ionosphere as the angle increases.

One of biggest problems for GPS accuracy is that changing atmospheric conditions change the speed of the GPS signals unpredictably as they pass through the ionosphere. The receiver is able to determine exactly when the signals were received by adjusting its internal clock (and therefore the spheres' radii) so that the spheres intersect near one point. Fortunately, even the relatively simple clock within the receiver provides an accurate comparison of the timing of the signals from the different satellites. One complication is that GPS receivers do not have atomic clocks, so the precise time is not known when the signals arrive.

In practice, GPS calculations are more complex for several reasons. Once the location and distance of each satellite is known, the receiver should theoretically be located at the intersection of four imaginary spheres, one around each satellite, with a radius equal to the time delay between the satellite and the receiver multiplied by the speed of the radio signals. Each satellite uses a different sequence, which lets them share the same radio frequencies, using Code Division Multiple Access, while still allowing receivers to identify each satellite. In order to measure the delay, the satellite sends a repeating 1,023 bit long pseudo random sequence; the receiver knows the seed of the sequence, constructs an identical sequence and shifts it until the two sequences match.

The receiver calculates the orbit of each satellite based on information encoded in their radio signals, and measures the distance to each satellite, called a pseudorange, based on the time delay from when the satellite signals were sent until they were received. GPS receivers calculate their current position (latitude, longitude, elevation), and the precise time, using the process of trilateration after measuring the distance to at least four satellites by comparing the satellites' coded time signal transmissions. Each satellite repeatedly broadcasts its own orbital elements, and a precise time-code. They regularly synchronize the atomic clocks onboard each satellite, and send updates to the satellites of their observed position in orbit.

Ground-based observatories around the world monitor the flight paths of the GPS satellites. [5]. The orbits are designed so at least four satellites are always within line of sight from almost any place on earth. Each satellite circles the Earth twice each day at an altitude of 20,200 kilometres (12,600 miles).

The GPS system is made up of a satellite constellation of 24 working satellites and three spares in intermediate circular orbits, in 6 orbital planes. The oldest GPS satellite still in operation was launched in February 1989. The most recent launch was in September 2005. [4].

The first modern Block-II satellite was launched in February 1989, and a complete constellation of 24 satellites was in orbit by 1993. By 1985, ten more experimental Block-I satellites had been launched to validate the concept. In 1983, after Soviet jet interceptors shot down the civilian airliner KAL 007 in restricted Soviet airspace, killing all 269 people on board, Ronald Reagan announced that the GPS system would be made available for civilian uses once it was completed. The GPS satellites were initially manufactured by Rockwell and now manufactured by Lockheed Martin.

The first experimental Block-I GPS satellite was launched in February 1978 [3]. It was only a small leap of logic to realize that the converse was also true; if the satellite's position was known then they could identify their own position on Earth. They realized that since they knew their exact location on the globe, they could pinpoint where the satellite was along its orbit by measuring the Doppler distortion. They discovered that, due to the Doppler effect, the frequency of the signal being transmitted by Sputnik was higher as the satellite approached, and lower as it continued away from them.

Kershner were monitoring Sputnik's radio transmissions. Richard B. scientists led by Dr. A team of U.S.

The inspiration for the GPS system came when the Soviets launched the first Sputnik in 1957. However, this is usually corrected on the display within 15 minutes once the UTC offset message is received for the first time. New GPS units will initially show the incorrect time after achieving a GPS lock for the first time. Receivers thus apply a clock-correction offset (which is periodically transmitted along with the other data) in order to display UTC correctly, and optionally adjust for a local time zone.

Today, GPS time is 14 seconds ahead [2] of UTC, because it does not follow leap seconds. The atomic clocks on the satellites are set to "GPS time", which is the number of seconds since 00:00:00 UTC, January 6, 1980. For instance, when deploying sensors (for seismology or other monitoring application), GPS may be used to provide each recording apparatus with some precise time source, so that the time of events may be recorded accurately. Many synchronization systems use GPS as a source of accurate time, hence one of the most common applications of this use is that of GPS as a reference clock for time code generators or NTP clocks.

This allows the data to be reported in real-time, using either web browser based tools or customized software. The recorded data can be stored within the tracking unit, or it may be transmitted to a central location, or internet-connected computer, using a cellular modem, 2-way radio, or satellite. A GPS tracking system uses GPS to determine the location of a vehicle, person, or pet and to record the position at regular intervals in order to create a track file or log of activities. On the other extreme, some airlines integrate GPS tracking of the aircraft into their aircraft's seat-back television entertainment systems, available even during takeoff and landing to all passengers.

Additionally, some airline companies disallow use of hand-held receivers for security reasons, such as unwillingness to let ordinary passengers track the flight route. Most airlines allow private use of ordinary GPS units on their flights, except during landing and take-off, like all other electronic devices. Geocaching often includes walking or hiking to natural locations, and is popular with both children and adults. Geocaching involves using a hand-held GPS unit to travel to a specific longitude and lattitude to search for objects deliberately hidden there by other Geocachers.

The availability of hand-held GPS receivers for a cost of about $90 and up (as of March 2005) has led to recreational applications including Geocaching. For information about navigation systems for the visually impaired, including MoBIC, Drishti, Brunel Navigation System for the Blind, NOPPA, BrailleNote GPS, and Trekker, refer to the main article GPS for the visually impaired. More costly and precise receivers are used by land surveyors to locate boundaries, structures, and survey markers, and for road construction. Low cost GPS receivers are often combined in a bundle with a PDA, car computer, or vehicle tracking system.

Glider pilots use the logged signal to verify their arrival at turnpoints in competitions. Hand-held GPS receivers can be used by mountain climbers and hikers. The system can also be used by computer controlled harvesters, mine trucks and other vehicles. GPS is used by people around the world as a navigation aid in cars, airplanes, and ships.

Commercial civilian GPS receivers are required to have limits on the velocities and altitudes at which they will report coordinates; this is to prevent them from being used to create improvised missiles. The satellites also carry nuclear detonation detectors, which form a major portion of the United States Nuclear Detonation Detection System. GPS allows accurate targeting of cruise missiles and precision-guided munitions (or "smart bombs"), as well as improved command and control of forces through improved locational awareness. .

Although the cost of maintaining the system is approximately US$400 million per year, including the replacement of aging satellites, GPS is available for free use in civilian applications as a public good. The satellite constellation is managed daily by the 2d Space Operations Squadron at Schriever Air Force Base. United States Department of Defense developed the system, officially named NAVSTAR GPS (Navigation Signal Timing and Ranging Global Positioning System). GPS accuracy can be improved further, to about 1 cm (half an inch) over short distances, using techniques such as Differential GPS (DGPS).

The Wide-Area Augmentation System (WAAS), available since August 2000, increases the accuracy of GPS signals to within 2 meters (6 ft) [1] for compatible receivers. GPS also provides an extremely precise time reference, required for some scientific research, including the study of earthquakes. Since GPS was declared fully operational in 1993, it has become a vital global utility, indispensible for modern navigation on land, sea, and air around the world, as well as an important tool for map-making, and land surveying. A constellation of more than two dozen GPS satellites broadcasts precise timing signals by radio to electronic GPS receivers which allow them to accurately determine their location (longitude, latitude, and altitude) in real time, day or night, in any weather.

The Global Positioning System, usually called GPS, is the Earth's only fully-functional satellite navigation system. GPS Anti-Jamming Protection. The hunt for an unintentional GPS jammer. GPS jamming.

noaa.gov Selective Availability Factsheet (pdf) or [10]. This is similar in principle to the combination of GPS and inertial navigation used in ships and aircraft, but less accurate and less expensive because it only fills in for short periods. Many automobile GPS systems combine the GPS unit with a gyroscope and speedometer pickup, allowing the computer to maintain a continuous navigation solution by dead reckoning when buildings, terrain, or tunnels block the satellite signals. This can be accomplished by using a combination of differential GPS (DGPS) correction data, transmitting GPS signal phase information and ambiguity resolution techniques via statistical tests—possibly with processing in real-time (real-time kinematic positioning, RTK).

This is done by resolving the number of cycles in which the signal is transmitted and received by the receiver. In this approach, accurate determination of range signal can be resolved to an accuracy of less than 10 centimetres. Relative Kinematic Positioning (RKP) is another approach for a precise GPS-based positioning system. Wide Area GPS Enhancement (WAGE) is an attempt to improve GPS accuracy by providing more accurate satellite clock and ephemeris (orbital) data to specially-equipped receivers.

CPGPS working to within 1% of perfect transition matching can achieve 3 mm ambiguity; in reality, CPGPS coupled with DGPS normally realizes 20-30 cm accuracy. The phase difference error in the normal GPS amounts to a 2-3 m ambiguity. CPGPS solves this problem by using the L1 carrier, which has a period 1/1000 that of the C/A bit width, to define the transition point instead. A successful correlation could be defined in a number of various places along the rising/falling edge of the pulse, which imparts timing errors.

The problem arises from the fact that the transition from 0-1 or 1-0 on the C/A signal is not instantaneous, it takes a non-zero amount of time, and thus the correlation (satellite-receiver sequence matching) operation is imperfect. This technique utilizes the 1.575 GHz L1 carrier wave to act as a sort of clock signal, resolving ambiguity caused by variations in the location of the pulse transition (logic 1-0 or 0-1) of the C/A PRN signal. A Carrier-Phase Enhancement (CPGPS). Exploitation of DGPS for Guidance Enhancement (EDGE) is an effort to integrate DGPS into precision guided munitions such as the Joint Direct Attack Munition (JDAM).

These correction data are typically useful for only about a thirty to fifty kilometer radius around the transmitter. But in this case, the correction data are transmitted from a local source, typically at an airport or another location where accurate positioning is needed. This is similar to WAAS, in that similar correction data are used. A Local Area Augmentation System (LAAS).

However, variants of the WAAS system are being developed in Europe (EGNOS, the Euro Geostationary Navigation Overlay Service), and Japan (MSAS, the Multi-Functional Satellite Augmentation System), which are virtually identical to WAAS. The current WAAS system only works for North America (where the reference stations are located), and due to the satellite location the system is only generally usable in the eastern and western coastal regions. Although only a few WAAS satellites are currently available as of 2004, it is hoped that eventually WAAS will provide sufficient reliability and accuracy that it can be used for critical applications such as GPS-based instrument approaches in aviation (landing an airplane in conditions of little or no visibility). This uses a series of ground reference stations to calculate GPS correction messages, which are uploaded to a series of additional satellites in geosynchronous orbit for transmission to GPS receivers, including information on ionospheric delays, individual satellite clock drift, and suchlike.

The Wide Area Augmentation System (WAAS). The "difference" is broadcast as a local FM signal, allowing many civilian GPS receivers to "fix" the signal for greatly improved accuracy. Differential GPS (DGPS) can improve the normal GPS accuracy of 4-20 meters to 1-3 meters.[8] DGPS uses a network of stationary GPS receivers to calculate the difference between their actual known position and the position as calculated by their received GPS signal. Bradford Parkinson, teacher of aeronautics and astronautics at Stanford University developed the system.

Ivan Getting, emeritus president of The Aerospace Corporation and engineer at the Massachusetts Institute of Technology established the basis for GPS, improving on the World War II land-based radio system called LORAN (Long-range Radio Aid to Navigation). The first Block IIF satellite that would provide this signal is set to be launched in 2007. This frequency falls into an internationally protected range for aeronautical navigation, promising little or no interference under all circumstances. L5 (1176.45 MHz):
Proposed for use as a civilian safety-of-life signal.

L4 (1841.40 MHz):
Being studied for additional ionospheric correction. L3 (1381.05 MHz):
Carries the signal for the GPS constellation's alternative role of detecting missile/rocket launches (supplementing Defense Support Program satellites), nuclear detonations, and other high-energy infrared events. Recognizing the civilian need for increased accuracy, "modernized" IIR-M (IIR-14 (M) and later) satellites carry a civilian signal interleaved with an improved military signal on both the L1 and L2 frequencies. In spite of not having the P(Y) code encryption key, several high-end GPS receiver manufacturers have developed techniques for utilizing this signal (in a round-about manner) to increase accuracy and remove error caused by the ionosphere.

The keys are changed on a daily basis. government and are generally provided only for military use. The encryption keys required to directly use the P(Y) code are tightly controlled by the U.S. L2 (1227.60 MHz):
Usually carries only the P(Y) code.

L1 (1575.42 MHz):
Carries a publicly usable coarse-acquisition (C/A) code as well as an encrypted precision P(Y) code. Precise time reference. GPS tracking. GPS on airplanes.

Geocaching. GPS for the visually impaired. Surveying. Navigation.

Military Applications.