Archive for 'Gps'

What is GPS? The acronym stands for Global Positioning System. It is the new “Polaris” that aids in navigating, positioning and tracking with the use of a satellite-controlled system that broadcasts signals to the equipment on the ground. With receivers hand carried by users, GPS determines the exact location of a vehicle, person or assets and other things useful and valuable to which it is attached and records the position at regular intervals. It is a powerful tracking system that has provided the world with diverse applications for the military and civilian users.

What is GPS? The GPS is a space-based radionavigation system controlled and funded by the U.S. Department of Defense and operated by the U.S. Military. This is the GPS Operational Constellation. The tracking system has space segments consisting of GPS satellites sending signals coming from space. There can be at least 24 operational satellites orbiting in 12 hours that recapitulate the same ground track as the earth turns underneath them. The GPS satellites then transmit the data in a very precise time reference plied by what is called “atomic clocks” onboard the satellite. These atomic clocks then passively transmit the navigation messages in specially coded signals, enabling the equipment on the ground called “receivers” to compute position, time, direction and velocity in three-dimensional locations known as latitude, longitude and altitude.

What is GPS? Your Most Reliable and Most Precise Assistant

The GPS was primarily for the use of the military. However, after the Korean Flight 007 in 1983 tragedy, which would have been prevented had its crew only had access to better navigational tools, President Ronald Reagan issued a directive which would guarantee that GPS signals be made available to the world for free or without restrictions. Though it was intended for civilians as well as military applications at first, from its design, civilian users would not be getting the same accuracy that the military could.

Going public, what is GPS serving the commercial market? GPS became the new powerful tool that improved efficient routing of vessels at sea. It has saved a ship’s navigator hours of celestial inference and calculation. GPS enhanced safety at sea made it possible to report precise position to rescuers in case of disasters.

What is GPS navigating the land? GPS also improved efficiency on land: delivery trucks can now receive GPS signals and easily transmit their position back to a central dispatcher; police and fire departments use GPS to efficiently dispatch their vehicles and reduced response time; GPS keeps motorists from getting lost by showing their position and intended route on dashboard displays; railroads now use GPS technology in replacing older maintenance-intensive mechanical signals.

What is GPS navigating the air? Long before the GPS, aircrafts typically fly from one waypoint to another and pilots on long-distance flights relied on navigational beacons situated across the country. The dawning of GPS supplemented existing navigational techniques for aircrafts inexpensively. With GPS navigating the air, airplanes can now fly a direct route to a destination that save significant amount in consumption of fuel and time, the methods of guiding planes to a safe landing in a poor weather or visibility has been improved and simplified and aided pilots with a precise position data to keep the plane on course.

What is GPS surveying, mapping the earth, managing the land and agriculture? GPS is used by surveyors and map makers for precision positioning; map locations of such facilities as telephone poles, sewer lines, and fire hydrants; map construction sites and property lines in minutes. In mapping the earth, GPS points have assigned codes in order to identify roads, streams, or other objects during data collection for analyses and comparison through a computer program called “Geographic Information Systems (GIS).”

GPS can be used in forestry, for mineral exploration, and wildlife habitat management to define positions of important assets precisely and identify their changes. In agriculture, a farm equipment with GPS receivers can provide precise position information and it also gives farmers great accuracy in the application of fertilizers and harvesting crops.

Agricultural GPS systems can be used to create crop yield maps during harvesting, making it easy for farmers to plan exactly how the fields should be used and fertilized for future crops.

So, what is GPS? It is a powerful navigational tool acting as your most reliable and most precise assistant that is transforming the way nations operate in space.

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Anyone who has used a great GPS system, including a great motorcycle GPS system, will know how user friendly and useful a good GPS can be. With modern GPS technology coming of age and modern digital mapping technology improving, a great motorcycle GPS can turn a ride into a pleasure.

What is GPS? For those who don’t know, GPS stands for Global Positioning System. It is a navigation and positioning technology pioneered by the US army, that has been taken to it’s ultimate and turned into a complete user friendly modern navigation solution. Whilst in the past GPS was really just the province of the military, the technology is now so good, and so cheap, that anyone needing the ultimate in navigation can afford it.

That includes motorcyclists, modern motorcycle GPS has also come of age.

Basically GPS works by cross referencing the signals from a number of satellites above the head of the user and using those references to plot the user’s position on the globe. It will only work where there are available satellites, so if you can’t pick up the signals your GPS won’t work.

Modern GPS is accurate, depending on the number of satellites available, to within less than a yard. So anyone seeking to navigate by use of a GPS system can obtain extremely accurate positioning. And this is now user friendly. In the past this information was only available as a longitude and latitude figure. This was only really useful to someone with the technical expertise to actually use this to plot the position on a map.

However now modern GPS, including high quality motorcycle GPS systems, can combine digital mapping technology with GPS positioning to produce an extremely user friendly outcome. Basically the position plotted by the GPS can be overlaid onto a digital map to show the GPS user, including the motorcyclist, their exact position on a digital map, and tell them how to get from where they are to where they want to go.

So motorcyclists can now buy dedicated motorcycle GPS systems that they can use as a total navigation system. There are various ways they can do this. It’s quite possible for the motorcycle rider, who may also, for example, be a keen hiker, to get a handheld portable GPS unit that can be taken anywhere, including mounted on a motorcycle. Download and install some maps that cover the area you want to navigate in and portable GPS can be used by just about anyone just about anywhere.

There are, however, some drawbacks using portable GPS for a motorcycle GPS system. When mounted on a motorcycle a GPS unit needs some special qualities. It needs to be vibration resistant, as a motorcycle has vibrations. It needs to be weather resistant as any equipment on a motorcycle will be out in the weather, including the rain. And it needs to be readable in all conditions, including direct sun.

And a motorbike rider needs to be able to program or use it whilst wearing heavy motorcycle gloves.

Luckily there are some excellent GPS manufacturers who have come to the rescue of the motorcyclist by manufacturing dedicated motorcycle GPS systems that combine all these features and more. The GPS mounts are designed to allow mounting without the problems of vibration, and the GPS units are vibration resistant, waterproof and can be read, and used, by the motorcyclist.

And even better, the best motorcycle GPS units can be used without the need for reading the screen. With bluetooth technology built in they can send directions by voice direct to the helmet of the motorbike rider, so the rider doesn’t need to take his eyes off the road.

Program in where you want to ride and it will take you there every turn, turn by turn. Ask it to and it will tell you all the places of interest along the way, like food or fuel stops, and accommodation. With the right extras it will even tell you in real time where the traffic jams are and how to ride around them. This saves you both time and fuel.

And along the way your motorcycle GPS unit may even allow you to play your favorite music or do the odd phone call or three.

And a good motorcycle GPS system should set you back less than $1000. It’s money extremely well spent for a motorcyclist who likes long, hassle free rides.

So if you ride a motorbike, and have a lazy $1000, you can’t do better than spending it on a quality motorcycle GPS system. It will repay you over and over.

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GPS principles

The basic principle of GPS navigation system to measure the known location of the satellite to the user the distance between the receiver and then integrated multi-satellite data can know the exact location of the receiver. To achieve this purpose, the satellite’s position can be based on-board clock time recorded in the satellite ephemeris identified. The user to the satellite’s distance from the satellite signal transmitted through the records to the user the experience of time, and then multiplied by the speed of light received (due to the interference of the atmosphere ionosphere, this distance is not the user and the real distance between the satellites, but pseudorange (PR): When the GPS satellites to work, it will continue to use 1 and 0 binary symbol composed of pseudo-random number (PN for short) launched navigation message. GPS pseudo-code system uses a total of two, namely civilian C / A code and the military of the P (Y) code. C / A code frequency 1.023MHz, repeat cycle of a millisecond, the code distance one microsecond, equivalent to 300m; P code frequency of 10.23MHz, repeat the cycle of 266.4 days, Code spacing of 0.1 microseconds, equivalent to 30m. The P code Y code is formed on the basis of confidentiality better performance. navigation message includes satellite ephemeris, work status, clock corrections, ionospheric delay correction, atmospheric refraction correction and other information. It is in the solution from the satellite signal modulation up to 50b / s modulation in the carrier frequency on the launch. navigation data included in each of the main frame 5 sub-frames per frame size 6s. the first three frames of all 10 code; repeat every 30 seconds, updated hourly. After the two were 15000b. navigation message in the contents of the main remote codes, code conversion, the first data blocks 1,2,3, including the most important was ephemeris data. When the user receives the navigation data, the extraction of the satellite time and do it with their own clock compared satellite and the user will be aware of the distance, and then use the navigation data in the satellite ephemeris data, calculate the location of the satellite launch when the message the user in WGS-84 geodetic coordinate system position, velocity and other information can be learned.
GPS satellite navigation system can be seen part of the role is to constantly launch navigation message. However, users accept the machine using the onboard clock with the clock can not always synchronized, so in addition to the user’s three-dimensional coordinates x, y, z, but also introduce a ?t is the time between the satellite and receiver differential as unknown, then four equations out of these four unknown solution. So if you want to know the location of the receiver, at least four satellites can receive the signal.
GPS receiver can receive the exact timing can be used to nanosecond time information; for forecasting the next few months in which broad locations satellite ephemeris; used to calculate the required positioning satellite coordinates of the broadcast ephemeris a precision of several meters to tens of meters (each satellite is different at any time change); and GPS system information, such as satellite status.
GPS receiver of the code can be measured from the satellite to the receiver, as with the receiver clock error of satellite and atmospheric propagation errors, it is called pseudorange. 0A code measured on the pseudo-range as UA code pseudorange, the accuracy is about 20 meters, measured on the P code pseudo-range as P code pseudo-range, precision is about 2 meters.
GPS receiver to receive satellite signals, decode or use other technology, the information on modulation in the carrier removed, you can restore the carrier. Strictly speaking, the carrier phase should be known as the carrier beat phase, which is received by the Doppler frequency shift effects of the satellite signal carrier phase and the receiver local oscillation signal phase difference. Generally determined by the receiver clock time measurement epoch, to keep track of the satellite signal, you can record changes in the value of the phase, but the start time of observation and satellite receiver initial phase of the oscillator is not known, since epoch beginning phase integer not know about that ambiguity, only as a parameter in the Data Processing Solution. Phase observations are accurate to the millimeter, but only solved ambiguity, only the relative positioning, and continuous observation for some time to use the phase observations, and to achieve better than the meter-level positioning accuracy of only phase observations can be used.
By positioning mode, GPS positioning into a single point positioning and relative positioning (differential positioning). Single point positioning is only one receiver according to the observation data to determine the way the receiver position, it can only use pseudorange measurements can be used for rough travel, etc. navigation. Relative positioning (differential position) is based on two or more receivers of observational data to determine the relative position between the observation points the way, both can be used pseudorange phase measurements can be applied, geodetic or engineering survey shall be phase observations using the relative positioning.
In the GPS observables includes satellite and receiver clock error, atmospheric propagation delay, multipath effects, etc. error, even when in the position calculation by the satellite broadcast ephemeris error, and during most of the public when the relative positioning error was offset or reduced, thus positioning accuracy will be greatly enhanced, dual-frequency receiver can view the two frequency ionospheric measurement error of the atmosphere to offset a major part in the high precision, when the distance between the receiver (there is significant difference between the atmosphere ) should be used in dual-frequency receiver.

Relativity for the GPS provides the necessary amendments
Global Positioning System GPS satellite timing signals to provide latitude, longitude and altitude information, accurate distance measurement requires precise clock. Therefore, we must use precise GPS receivers relativistic effect.
Accuracy within 30 meters in GPS receiver means that it has made use of the relativistic effect. University of Washington physicist Clifford M. Will explained in detail, said: “If you do not take into account relativistic effects, satellite clock on the Earth’s clock is not synchronized.” Relativity that fast moving objects with the passage of time slower than static. Will calculated for each GPS satellite approximately 1.4 million kilometers per hour across the distance, which means its on-board atomic clocks on Earth every day the clock slower than 7 microseconds.
The gravitational force exerted on time more relativistic effects. About 2 million meters of altitude, GPS satellites by the gravitational pull by approximately one quarter of the ground. The result is that on-board clock speed of 45 microseconds per day, GPS should be included in a total deviation of 38 microseconds. Ashby explained: “If there is no satellite frequency compensation of 11 km per day will increase the error.” (This effect is in fact more complex, because the satellite along an eccentric orbit, sometimes closer from Earth, sometimes Also very near.)

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WAAS-Enabled GPS System



Jeff Sanders

Garmin GPS Navigation Systems

www.GpsFrontier.com

04/05/09



WAAS-Enabled GPS System

WAAS (Wide Area Augmentation System) was developed by the Federal Aviation Administration to augment the Global Positioning System to improve its accuracy, integrity, and availability. WAAS was originally intended to enable aircraft to rely on GPS for all phases of flight, including the precision approach to airport’s within its coverage area. The WAAS system typically provides better than 1.0 meters laterally and 1.5 meters vertically throughout most of the contiguous United States and large parts of Canada and Alaska. This accuracy is capable of provideing aircraft with the precision needed for safe approaches and inflight navigation for all weather conditions. Integrity of the WAAS information is no more than 3 seconds of bad data per year allowing the system to be considerd safe by the FAA for instrument flight rules.

Although orignally developed for aviation, WAAS is not just limited to the aviation industry, any GPS receiver that is capable of receiving the WAAS signal will be able to benefit from it’s correction data, making the GPS positioning more accurate. In fact a WAAS-enabled GPS receiver can even give you directions right down to the lane your car is traveling in (as long as the maping program supports “lane assist” directions). Because the Wide Area Augmentation System is quickly becoming standard in the GPS industry, most new GPS receivers today are WAAS-enabled. Just like with the conventinal GPS, the WAAS system doesn’t come with any extra cost or fees to use. All that is required is that the GPS receiver be WAAS-enabled so it can receive and decode the data then be able to apply corrections to it’s position. Currently the WAAS service is limited to the U.S.A., Canada, Alaska and Hawaii. Although independant from WAAS, Europe and Asia are working on their own supplemental GPS correction systems. Europe has the “Euro Geostationary Navigation Overlay Service” (EGNOS) and Japan is working on their “Multi-Functional Satellite Augmentation System” (MSAS) .



How The WAAS System Works

WAAS uses a network of approximately 25 ground based Wide-area Reference Stations (WRS) in North America and Hawaii, to measure small variations in GPS satellite signals in the western hemisphere. These precisely surveyed ground stations monitor and collect information on the GPS signals and send their data to the three Wide-area Master Stations (WMS). The WMS’s generate two different sets of corrections: fast and slow. The fast corrections are for errors that are changing rapidly and are a primary concern to the GPS satellites instantaneous positions and clock errors. These corrections are user position independent, which means they can be applied instantly by any receiver in the WAAS broadcasting area. The slow corrections are for long-term ephemeric and clock error estimates and ionospheric delay information.

Once these corrections are generated, the Master Stations sends them to two pairs of Ground Uplink Stations (GUS) that transmit the correction messages to a series of geostationary satellites that broadcast their correction data back to earth. Then WAAS-enabled GPS receivers use this information to make corrections to the original GPS signial, giving WAAS-enabled GPS receiver a more accurate position. GPS receiver’s use the information broadcast from each GPS satellite to determine their location and the current time. Depending on the GPS device, a GPS receiver only needs to receive a signal from 3-4 satellites (out of the 31 satellites currently transmiting a signal for civilan users) to be able to calculate it’s position. In addition to the GPS signal, a WAAS-enabled GPS receiver can also receive the geostationary WAAS satellite signal.

The two different types of correction messages from the WAAS system (fast and slow) are used by the GPS receiver in different ways. The fast type of correction data includes the corrected satellite position and clock data to determine its current location using normal GPS calculations. Once an approximate position fix is obtained the GPS receiver begins to use the slow corrections to improve its accuracy. Slow correction data Includes the ionospheric delay. When the GPS signal travels from the satellite to the receiver, it passes through the ionosphere. The receiver calculates the location where the signal pierced the ionosphere and, if it has received an ionospheric delay value for that location, it corrects for the error that the ionosphere created. Unlike the fast data, the slow data doesn’t need to be updated frequently because the ionosphere conditions don’t change rapidly. While the slow data can be updated every minute if necessary, they are only updated every two minutes and are considered valid for up to six minutes.



Limitations of the WAAS System

(1) The WAAS system is currently only available to United States and large parts of Canada and Alaska but there plans to expand the system to other countries and continents. (2) Because the WAAS broadcasting satellites are geostationary causes them to be less than 10° above the horizon for locations north of 71.4° latitude. This means aircraft in areas of Alaska or northern Canada may have difficulty maintaining a lock on the WAAS signal. (3) In order to calculate an ionospheric grid point’s delay, that point must be located between a satellite and a reference station. The low number of satellites and ground stations limit the number of points which can be calculated. (4) Aircraft conducting WAAS approaches must possess certified GPS receivers.

Jeff Sanders

Garmin GPS Navigation Systems

www.GpsFrontier.com

04/05/09


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GPS Navigation Systems have come a long way



Jeff Sanders

Garmin GPS Navigation Systems

http://www.GpsFrontier.com

04/05/09

GPS Navigation Systems have come a long way

Gps systems have come a long way since they were first designed for the US millitary. The first signal from NAVSTAR 1 was received on Feb. 22, 1978. NAVSTAR 1 was launched from Vandenberg Air Force Base in California and was the first of 24 satellites that make up the Global Positioning System (GPS). The first generation of satellites that make up the Global Positioning Systems 24 satellites were launched between Feb. 22, 1978 and Oct. 9, 1985. Since it First became operational the Global Positioning Systems has revolutionized the way America goes to war and provides a GPS system in which the world relies on for precise navigation.

The Global Positioning System’s constellation of orbiting satellites is managed by the United States Air Force 50th Space Wing. The unit is the host wing at Schriever Air Force Base, located in east Colorado Springs, Colorado. They are responsible for tracking and maintaining the command and control, warning, navigational, and communications satellites for Air Force Space Command as well as the Global Positioning System satellites. Full Operational Capability was declared by NAVSTAR in April 1995 (NAVSTAR is an acronym for NAVigation Satellite Timing and Ranging, and is the official U.S. Government name given to the GPS satellite system).

The US government granted the Global Positioning System available for civilian use in the late 1980s and with no subscription fees or setup charges to use the GPS system the civilian GPS market exploded, especially in the last decade. A new generation of sophisticated GPS satellites are replacing the older satellites and there are now 34 GPS satellites in orbit that provide combat capability for military applications and aircraft navigation aids. Civilian applications include ATM’s, bank and stock market transactions as well as power grid management. Currently 31 of the 34 GPS satellites in orbit transmit navigation and timing signals to civilian and military users around the world.

Gps for civilian use

The civilian GPS system wasn’t always as it is today and the US military is still keeping the most accurate Global Positioning Systems available classified for national security. But GPS upgrades for two new civilian signals to enhanced user accuracy and reliability, particularly with respect to aviation safety were planned in 1998. Then on May 2, 2000 “Selective Availability” was discontinued as a result of the 1996 executive order, allowing users to receive a non-degraded GPS signal globally, and in 2004 QUALCOMM announced the successful tests of assisted GPS for mobile phones that led the way for the GPS aided cell phones that are widely used today.

In 2005, the first third generation GPS satellite was launched and began transmitting a second civilian signal for enhanced user performance. Then in September of 2007 the Air Force completed a four-phase transition of the Global Positioning Systems ground segment to it’s new Architecture Evolution Plan. The ground segment’s provide command and control of the satellites and generates the navigation message for satellites to broadcast to the users GPS device to calculate their earth’s position. The new Gps satellites include new high-powered, anti-jam military-code, along with other accuracy, reliability, and data integrity improvements for both civil and military users. This modernized version of the world’s greatest free utility was designed to ensure the US has the most precise and secure positioning, navigation and timing capability through 2030.

Europe and Russia develop their own GPS

In 2004 the United States signed an agreement with the European Community establishing cooperation with Europe’s planned Galileo system. Galileo is a global navigation satellite system (GNSS) that is currently being built by the European Union and is separate from but complimentary to the United States Global Positioning System. The European Union’s Galileo system should be operational by 2013. The European Community’s political aim is to provide an independent GPS system that the European nations can rely on in times of war or political disagreement, because both Russia or the USA could disable use of their national systems by others (through encryption).

The Russian GPS system GLONASS is a radio-based satellite navigation system that was developed by the former Soviet Union and now operated for the Russian government by the Russian Space Forces. Like the European GPS system the Russian GPS system also functions separate from but is complimentary to the United States Global Positioning System. Russia began launching satellites for their GPS system into space on October 12, 1982 and was completed in 1995. The system rapidly fell into disrepair fallowing the collapse of the Russian economy but in 2001 the Russian government began restoring the system with hopes of restoring global coverage by the end of 2009.

GPS Systems today

Depending on the GPS unit a GPS receiver only needs a signal from 3-4 satellites to calculate the units position and will work in any weather conditions, anywhere in the world, 24 hours a day. There are no subscription fees or set up fees like with a cell phone to operate GPS receivers and although some GPS receivers have extra features like real time traffic updates that will have a monthly charge, some GPS receivers like Garmins Nuvi “T” series come with free live traffic for the life of the unit. Today’s GPS is extremely accurate thanks to their parallel multi-channel design. Garmin’s 12 parallel channel receivers are very quick to lock onto satellites when first turned on and they maintain a strong lock even in dense foliage or city’s with tall buildings because they continuously track signals from up to 12 satellites at any given time. Even if a 12 parallel channel GPS receiver loses signals from 8 satellites at once it will still function properly.

WAAS (Wide Area Augmentation System) was developed by the Federal Aviation Administration to augment the Global Positioning System to improve its accuracy, integrity, and availability. WAAS was originally intended to enable aircraft to rely on GPS for all phases of flight, including the precision approach to airport’s within its coverage area. All though originally intended for aviation most GPS receivers today are WAAS-enabled including automotive, boating chartplotters and hand-held units. WAAS uses a network of ground based reference stations, in North America and Hawaii, to measure small variations in the GPS satellites’ signals. Measurements from these reference stations are routed to master stations and then they send correction messages to geostationary WAAS satellites. Those satellites then broadcast the correction messages back to Earth, where WAAS-enabled GPS receivers use the correction data while computing their positions to improve accuracy. WAAS enabled GPS receivers are accurate to within 3 meters and that make them the most accurate GPS receivers for civilian use on the market today. In fact a WAAS-enabled GPS receiver can even give you directions right down to the lane your car is traveling in (as long as the mapping program supports “lane assist” directions) and With no additional equipment or fees required to take advantage of WAAS-enabled GPS receivers they are becoming as common as cell phone’s.


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