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Archive for the ‘Maps Waypoints’ Category

There’s nothing like cruising the open road on a motorcycle. My friends and I especially like journeying back roads where the scenery makes me glad I’m a biker. We seek out the roads less traveled and these days we’ve found infinite paths available to us thanks to my GPS maps. You have to know more about it by reading the article below.

I have a Nuvi 350 – an old model when I bought it a year and a half ago, but it’s still going strong. It’s a nice waterproof model that I mount on my motorcycle for easier touring. And the GPS maps are fantastic.

Now here’s the exciting thing. My Nuvi lets me plan routes on my computer and upload them as GPS maps. Very nice when I want to plan out a nice ride using info from other riders. The Nuvi’s are point-to-point devices, although I can put a single waypoint in either (stop at the grocery on the way to work, for example). The higher end Nuvi units now have multiple waypoint routing, so you could fake a planned ride by just putting in waypoints at any of the big intersections on a planned ride.

The only drawback I’ve found is that sometimes roads change names in towns and back roads and the name you’re given may not be the same as the name the GPS map uses at that time. But with the GPS itself I don’t have to worry that I’ll get lost. I can just “map” my way back or find an alternative route home.

 

By Michael Webster: Syndicated Investigative Reporter. May 17, 2010 at 4:30 PM PDT

1st part in a multiple part series.

 

Americans on the American side of the U.S. Mexican border are in much danger today from newly trained Mexican drug traffickers, who according to the highest level of the Mexican military reveals that Mexican Drug Cartels (MDC’s) are currently training Mexican smugglers in the art of military tactic’s. These trainees often referred to by many as coyotes are very important to the drug trade. These coyotes are believed to be responsible for the tons of illegal drugs being clandestinely smuggled into the United States from Mexico on a daily bases. As a result of this new level of training it is putting many average Americans in crave danger and right here at home.

A high ranking Mexican Army commander who insists on remaining anonymous has told the U.S. Border Fire Report that Mexican coyotes are now being trained by the Mexican Drug Cartel known as the Los Zetas and are operating in the deserts of Arizona. These highly trained former Mexican Army solders who themselves went through some of the best and latest U.S. Army training at the American tax payers expense now are passing this training onto the front line drug smugglers that guide these drug loads and human beings into the states mainly through our southern border with Mexico. They’re known as “Los Zetas

 

 See video’s at: http://www.secureborderintel.org/TusconSector-armedescorts.html 

This new breed of coyote now operate as a fine tuned military unit. I was able to make contact and talk with one of these new Zetas coyote smugglers. The deal was, if I would agree to not take any photo’s or know his real name he would talk with me.

So I’ll call him Juan. Juan told me that he had been guiding people into the USA for years and said he made a  good living for him and his family of 7 kids and a wife. He said he was approached a couple of years ago by a Los Zetas officer who offered him military training and lots more money. Juan said that he picked 5 of his best workers who over the years had help him with his guiding business and they all went to a Zetas’s camp for 9 weeks of training. He says ” that he now makes much more money” he went on to say with this new training and man power he’s able to bring many more people and loads of drugs into the US via the U.S. Mexican border. He said that where he once was paid 100 U.S. dollars per person  (Illegal Alien) and 500 per pack mule (drug carrier) He now makes much more than that.

He confided that he and many others now as Los Zetas’s operatives run five (5) man armed squads who lead both people who want to come to America and drug smuggling mules across the Arizona desert. ” One of the members of his team runs point, two or more on each side of the group when possible or otherwise imbedded within the middle range of the group. Another brings up the rear as a tail gunner each carrying an AK 47 and the tail gunner packing a M-60 machine gun and or a 12 gouge riot shot gun. The groups range in size from 4 or five to a hundred or more per trip.

 

He, told me “that the weapons are used to guarantee the success of the operation”. He said “there are many dangers I and my men can face in route, me and my men have used our weapons to protect the group against Rattle Snakes and even Bear attacks” 06/08/09 - 10 second video – bear on trail.  But later he admitted that the main reason for having the weapons is to protect the drugs, mainly from competing drug gangs who from time to time they encounter. According to him many of the roaming gangs are looking for a fast and easy load of drugs, But also there are competing drug cartel gangs who are also trained and will try to take our loads and who want to operate on our turf. “But now we are much better prepared to deal with this and other threats that we may have to face on every trip.” I asked, if and when he encounters American law enforcement would he and his men fire their weapons at them? He told me that that was not likely to happen because the routes he uses are not paroled by American authorities. He claims that this is possible because some high U.S. Government people is paid by the Zetas to not be in the area at certain times during his operations. He said ” we take additional precautions to prevent that from happening”. “We post our own people all along the route to I 8 and near the transfer points on the highway mile markers. We place our spotters on high ground and fly ultralight aircraft, both have communication equipment, radio’s and through away cell phones. They are paid to watch for authorities and intruders, such as gangs, dangerous animals, American tourist, hikers, campers and all others who may be in the area.”

 

Arizona estimates that there are up to million tourist known as snow birds who migrate to Arizona to winter each year, spending upwards of $1 billion dollars. Many of those snow birds camp, play and recreate on and near the dangerous U.S. Mexican Border in southern Arizona. Just like birds flying south for the winter, human residents of cold climates desire to escape the cold climates for a life of leisure. Most are unaware of the many dangers that the Mexican smugglers pose to there safety. There are signs posted on much of the Government lands warning visitors to the dangers that they my face if encountered by these dangerous smugglers.  Juan, told me he is retiring, that he has made a lot of money in the last couple of years and he is going to leave his business to one of his younger associate operative from which he expects to receive payments from him for years to come. Juan is moving his family to Colorado to live the American dream.

  

The U.S. Drug Enforcement Administration (DEA) considers Los Zetas to be the most dangerous drug-trafficking organization in Mexico. Its members earned a reputation as super-gangsters adept at paramilitary-style ambushes and bold jailbreaks.

On the Texas-Mexico border, the Zetas are mythic, their crimes chronicled in the media and memorialized in narco-ballads.

They are the most feared, most emulated criminals in Mexico.

“They are a formidable criminal organization,” says Anthony Placido, the DEA’s chief of intelligence. “They’re heavily armed with .50-caliber sniper rifles and heavy and light military-grade ordnance.”

“They are every bit as ferocious and as capable as a military force as some of the rumors believe them to be,” Placido says.

Originally, there were 31 Zetas — elite army counter-narcotics commandos who defected to work as enforcers for the Gulf Cartel. The name came from their radio code, the letter Z.

But after the 2003 arrest of Gulf crime boss Osiel Cardenas, “the lion wised up and now controls the handler,” as one observer put it.

The Zetas have morphed into their own cartel. Their zone of influence ranges from the lower Texas border, south along the Atlantic and Caribbean coastal states of Mexico, through Chiapas and all the way into Guatemala, where they trans-ship South American cocaine to Mexico.

But their base remains the charmless industrial border cities in the Mexican state of Tamaulipas.

Nuevo Laredo, in Tamaulipas, is the most important trade border crossing in Latin America — and it is Zeta territory.

From 2004 to 2007, the Zetas fought a savage turf war — which included bazooka and grenade attacks — against interlopers from the Sinaloa Cartel and others.

Zetas are now operating along the U.S. Mexican border from the Gulf of Mexico to the Pacific Ocean.

These newly trained Zata solders are currently enjoying a free rain to enter this country unmolested by American authorities  throughout the American Southwest where American Indian reservations, U.S. Military lands, National Parks, Monuments and U.S. forest lands are being penetrated and used by these smugglers, particularly in south central and south eastern Arizona and along the southern New Mexico border with old Mexico.

There are many gaps in the border that are not being effectively protected by American law enforcement and that at least in part is the reason concerned Americans have in the past formed minute man groups, armed themselves and patrolled the U.S. Mexican border and attempted to divert human and drug trafficking. In the past U.S. Army troops and National Guard units where also placed on the border. The U.S. has increased the numbers of the U.S. Border Patrol and Homeland security have beefed up border checks of travelers entering and exiting our country at known check points along the more than 2000 mile border with Mexico. Even with the billions of dollars having been spend on drug interdiction over the years as part of the war on drugs, the war on drugs is a failure.

 People being smuggled into the U.S. in the truck loads: Most are from Mexico. Central America, South America and even from China and the Middle east. Photo by SBI. Go to:  http://www.secureborderintel.org/Camera1-016.html

judge James Gray of Orange County California who has studied and worked with drug issues for years says “tens of billions of tax payer dollars have been spent on the War On Drugs and that so called war on drugs has failed.”

According to long time border observer Glen Spencer “A massive number of people illegally enter the USA every day by simply walking unchallenged across our southern border.   In the 1952 miles of border from California to Texas they use literally thousands of trails and paths, ever changing their routes to avoid detection.   Cartel involvement has brought increased organizational skills to smuggling operations and, contrary to government claims, only a very small percentage are apprehended.   Accurate statistics are impossible to gather, but the true numbers are staggering, and the general public remains largely uninformed. “

Now there are new groups forming and establishing their own organizations to monitor the situation on our southern border, one of these groups call themselves “Concerned Citizens” I recently had the opportunity to visit this low profile group as they organized monitoring and listening posts east of Gila Bend Arizona on and near I 8 a major U.S. highway that they claim is a transfer point of illegal aliens and loads of drugs on that highways many marker posts where they contend loads of human and drugs enter the U.S. through drug trafficking corridors originating in Mexico.

According to the Concerned Citizens of Arizona they want to alert the public to a new citizen activist opportunity to help them observe and report the daily invasion across our southern border with Mexico.

Daniel Webster said “This is not a Minuteman or extremist group sponsored event – just a call to action by a group of “Concerned Citizens”.

If you and or your group is interested you can contact them through e-mail: dtfsdf@oco.net 

Concerned Citizens report that DHS Secretary Janet Napolitano and the other race baiting, ethnocentric anarchists want the people of America to believe the border is under “operational control”. Nothing could be further from the truth says an organizer with the new group of “Concerned Citizens” and they have already have to deployed. They hope to video tape and educate Americans about the real threat to National Security and our public safety.

Concerned Citizens has a full blown showing of people who have come out and are enjoying our federal lands. This is people coming together to help AZ Governor Jan Brewer and the people of Arizona to bring attention to the need for National Guard on our southern border.

The group is in support of Jan Brewer signing SB1070 and say they want to help educate the public. they say “It’s time to bring back the” Minuteman Type Lines”

The group points out that there are 30 miles of area in a straight line that they cover.  They say that there propose is doing what they do best….. “DETERRENCE BY PRESENCE”

 

The operation was kicked off and started operations 15 May the operation is expected to least at least 2-3 weeks.

The locations of deployment is: Interstate 8, 45 miles south of downtown Phoenix

where they have placed multiple camps at major choke points.

 

This I-8 corridor is very active and “VERY DANGEROUS”, there is a very good chance you will see “ARMED DRUG LOADS”!! moving through the area.  This opp “IS NOT” for 1st timers, we are ready and at the top of our game with all the necessary gear for this type of opp and for being self sufficient for desert camping! Interstate 8, MM 141 – Freeman Exit

 

With that said, the biggest thing we can do on this opp is to be seen by the public on I-8 so we will be posting on every mile

    marker (that’s were all the action is anyway) for a 30 mi. stretch. We provide maps/intel/phone numbers and radios on site as, there should be 2 vehicles & 4 people min. per mi. marker for safety.

 

 

To the Concerned Citizens that are working I-8 and to those in the future thank you for supporting Arizona.

 

Concerned Citizens continue to do the job the Federal Government won’t do by securing the border south of Phoenix along Interstate 8. What we are having to do now is what should be done by Congress by putting Troops on the border.

The area south of Interstate 8 between Gila Bend (Junction 85 & I-8) and Casa Grande (Junction I-8 & I-10) is a major smuggling corridor…..drugs, IAs, weapons….. We’ve seen it all. This is approximately a 60 mile stretch, but not all that distance is active with smuggling.  The traffic comes up through the Tohono D’ O’dham Reservation day and night.

The fact that load vehicles use I-8 to enter this area, pick up their loads and leave the area makes them vulnerable to detection.  Load areas on I-8 are typically one of the following:  dirt roads, major washes and/or mile markers. Mile markers are used a “waypoints” by the load vehicles, so this also makes them vulnerable to detection.

Bottom line, if we had enough dedicated individuals “camped out” on the entire known active load up points on I-8, we could effectively shut this area down.  A lot of recon has been completed in this area so we know this is doable…. just a matter of enough dedicated individuals.

This IS a High Intensity Drug Trafficking Area and is potentially very dangerous so participating individuals who need to be prepared to defend tthemselves.

 t Abandon items found on the smuggling routes lift there by the smugglers and cleaned up by the Concerned Citizens. Photo By Concerned Citizens.

A long list of items, including abandoned vehicles, can be attributed to illegal aliens/ drug smugglers that traverse the desert.  Items such as used needles, drug paraphernalia, plastic grocery bags, paper products, empty water containers, blankets, bakpaks, clothing, used disposable diapers, sanitary napkins, etc are among things you might run across.  The heaps of litter long forgotten by those forging ahead come at a great cost to those who must bear the responsibility of cleaning it up. Each illegal alien leaves an average of 8 pounds of trash at layover and pickup areas. Statistics from the Border Patrol Tucson Sector report approximately 500,000 illegal aliens apprehensions in that sector for 2009.   Conservatively, the Border Patrol apprehends 1 in 5 illegal aliens so that means 2, 500,000 illegal aliens leaving 20 million pounds of trash every year in the Arizona Desert !

      

Many argue the government is not doing its job when it comes to securing the border especially with surveillance pictures snapped in March of heavily armed drug runners in a remote desert area near Casa Grande.

Pinal County Sheriff Paul Babeu says “it’s a known corridor for drug and human smuggling and it’s same area where Deputy Louis Puroll was shot during a gun battle with six smugglers, “he unloaded upon the suspects that were firing on him that were trying to kill him.”

Puroll was shot in the side and he believes he shot one of the suspects. Sheriff Babue says this latest round of border violence underscores the dangers his deputies face every day, “literally what it appears to be squad size elements using para military tactics that are either escorting largely drug loads or illegal’s.”

 

Global Positioning System

The Global Positioning System (GPS) is the only fully functional Global Navigation Satellite System (GNSS). Utilizing a constellation of at least 24 medium Earth orbit satellites that transmit precise microwave signals, the system enables a GPS receiver to determine its location, speed/direction, and time.

Developed by the United States Department of Defense, it is officially named NAVSTAR GPS (Contrary to popular belief, NAVSTAR is not an acronym, but simply a name given by Mr. John Walsh, a key decision maker when it came to the budget for the GPS program[1]). The satellite constellation is managed by the United States Air Force 50th Space Wing. The cost of maintaining the system is approximately US$750 million per year,[2] including the replacement of aging satellites, and research and development. Despite these costs, GPS is free for civilian use as a public good.

GPS has become a widely used aid to navigation worldwide, and a useful tool for map-making, land surveying, commerce, and scientific uses. GPS also provides a precise time reference used in many applications including scientific study of earthquakes, and synchronization of telecommunications networks.

Simplified method of operation

A GPS receiver calculates its position by measuring the distance between itself and three or more GPS satellites. Measuring the time delay between transmission and reception of each GPS microwave signal gives the distance to each satellite, since the signal travels at a known speed – the speed of light. These signals also carry information about the satellites’ location and general system health (known as almanac and ephemeris data). By determining the position of, and distance to, at least three satellites, the receiver can compute its position using trilateration.[3] Receivers typically do not have perfectly accurate clocks and therefore track one or more additional satellites, using their atomic clocks to correct the receiver’s own clock error.

[edit] Technical description

Unlaunched GPS satellite on display at the San Diego Aerospace museum

Unlaunched GPS satellite on display at the San Diego Aerospace museum

[edit] System segmentation

The current GPS consists of three major segments. These are the space segment (SS), a control segment (CS), and a user segment (US).[4]

[edit] Space segment

The space segment (SS) is composed of the orbiting GPS satellites, or Space Vehicles (SV) in GPS parlance. The GPS design calls for 24 SVs to be distributed equally among six circular orbital planes.[5] The orbital planes are centered on the Earth, not rotating with respect to the distant stars.[6] The six planes have approximately 55° inclination (tilt relative to Earth’s equator) and are separated by 60° right ascension of the ascending node (angle along the equator from a reference point to the orbit’s intersection).[2]

Orbiting at an altitude of approximately 20,200 kilometers (12,600 miles or 10,900 nautical miles; orbital radius of 26,600 km (16,500 mi or 14,400 NM)), each SV makes two complete orbits each sidereal day, so it passes over the same location on Earth once each day. The orbits are arranged so that at least six satellites are always within line of sight from almost everywhere on Earth’s surface.[7]

As of September 2007, there are 31 actively broadcasting satellites in the GPS constellation. The additional satellites improve the precision of GPS receiver calculations by providing redundant measurements. With the increased number of satellites, the constellation was changed to a nonuniform arrangement. Such an arrangement was shown to improve reliability and availability of the system, relative to a uniform system, when multiple satellites fail.[8]

[edit] Control segment

The flight paths of the satellites are tracked by US Air Force monitoring stations in Hawaii, Kwajalein, Ascension Island, Diego Garcia, and Colorado Springs, Colorado, along with monitor stations operated by the National Geospatial-Intelligence Agency (NGA).[9] The tracking information is sent to the Air Force Space Command’s master control station at Schriever Air Force Base in Colorado Springs, which is operated by the 2d Space Operations Squadron (2 SOPS) of the United States Air Force (USAF). 2 SOPS contacts each GPS satellite regularly with a navigational update (using the ground antennas at Ascension Island, Diego Garcia, Kwajalein, and Colorado Springs). These updates synchronize the atomic clocks on board the satellites to within one microsecond and adjust the ephemeris of each satellite’s internal orbital model. The updates are created by a Kalman filter which uses inputs from the ground monitoring stations, space weather information, and various other inputs.[10]

GPS receivers come in a variety of formats, from devices integrated into cars, phones, and watches, to dedicated devices such as those shown here from manufacturers Trimble, Garmin and Leica (left to right).

GPS receivers come in a variety of formats, from devices integrated into cars, phones, and watches, to dedicated devices such as those shown here from manufacturers Trimble, Garmin and Leica (left to right).

[edit] User segment

The user’s GPS receiver is the user segment (US) of the GPS system. In general, GPS receivers are composed of an antenna, tuned to the frequencies transmitted by the satellites, receiver-processors, and a highly-stable clock (often a crystal oscillator). They may also include a display for providing location and speed information to the user. A receiver is often described by its number of channels: this signifies how many satellites it can monitor simultaneously. Originally limited to four or five, this has progressively increased over the years so that, as of 2006, receivers typically have between twelve and twenty channels.

A typical OEM GPS receiver module, based on the SiRF Star III chipset, measuring 15×17 mm, and used in many products.

A typical OEM GPS receiver module, based on the SiRF Star III chipset, measuring 15×17 mm, and used in many products.

GPS receivers may include an input for differential corrections, using the RTCM SC-104 format. This is typically in the form of a RS-232 port at 4,800 bit/s speed. Data are actually sent at a much lower rate, which limits the accuracy of the signal sent using RTCM. Receivers with internal DGPS receivers can outperform those using external RTCM data. As of 2006, even low-cost units commonly include Wide Area Augmentation System (WAAS) receivers.

Many GPS receivers can relay position data to a PC or other device using the NMEA 0183 protocol. NMEA 2000[11] is a newer and less widely adopted protocol. Both are proprietary and controlled by the US-based National Marine Electronics Association. References to the NMEA protocols have been compiled from public records, allowing open source tools like gpsd to read the protocol without violating intellectual property laws. Other proprietary protocols exist as well, such as the SiRF and MTK protocols. Receivers can interface with other devices using methods including a serial connection, USB or Bluetooth.

[edit] Navigation signals

Main article: GPS signals

GPS broadcast signal

GPS broadcast signal

Each GPS satellite continuously broadcasts a Navigation Message at 50 bit/s giving the time-of-day, GPS week number and satellite health information (all transmitted in the first part of the message), an ephemeris (transmitted in the second part of the message) and an almanac (later part of the message). The ephemeris data gives the satellite’s own precise orbit and is output over 18 seconds, repeating every 30 seconds. The ephemeris is updated every 2 hours and is generally valid for 4 hours, with provisions for 6 hour time-outs. The time needed to acquire the ephemeris is becoming a significant element of the delay to first position fix, because, as the hardware becomes more capable, the time to lock onto the satellite signals shrinks, but the ephemeris data requires 30 seconds (worst case) before it is received, due to the low data transmission rate. The almanac consists of coarse orbit and status information for each satellite in the constellation and takes 12 seconds for each satellite present, with information for a new satellite being transmitted every 30 seconds (15.5 minutes for 31 satellites). The purpose of the data is to assist in the acquisition of satellites at power-up by allowing the receiver to generate a list of visible satellites based on stored position and time, while an ephemeris from each satellite is needed to compute position fixes using that satellite. In older hardware, lack of an almanac in a new receiver would cause long delays before providing a valid position, because the search for each satellite was a slow process. Advances in hardware have made the acquisition process much faster, so not having an almanac is no longer an issue. An important thing to note about navigation data is that each satellite transmits only its own ephemeris, but transmits an almanac for all satellites.

Each satellite transmits its navigation message with at least two distinct spread spectrum codes: the Coarse / Acquisition (C/A) code, which is freely available to the public, and the Precise (P) code, which is usually encrypted and reserved for military applications. The C/A code is a 1,023 chip pseudo-random (PRN) code at 1.023 million chips/sec so that it repeats every millisecond. Each satellite has its own C/A code so that it can be uniquely identified and received separately from the other satellites transmitting on the same frequency. The P-code is a 10.23 megachip/sec PRN code that repeats only every week. When the “anti-spoofing” mode is on, as it is in normal operation, the P code is encrypted by the Y-code to produce the P(Y) code, which can only be decrypted by units with a valid decryption key. Both the C/A and P(Y) codes impart the precise time-of-day to the user. Frequencies used by GPS include

* L1 (1575.42 MHz): Mix of Navigation Message, coarse-acquisition (C/A) code and encrypted precision P(Y) code, plus the new L1C on future Block III satellites.

* L2 (1227.60 MHz): P(Y) code, plus the new L2C code on the Block IIR-M and newer satellites.

* L3 (1381.05 MHz): Used by the Nuclear Detonation (NUDET) Detection System Payload (NDS) to signal detection of nuclear detonations and other high-energy infrared events. Used to enforce nuclear test ban treaties.

* L4 (1379.913 MHz): Being studied for additional ionospheric correction.

* L5 (1176.45 MHz): Proposed for use as a civilian safety-of-life (SoL) signal (see GPS modernization). This frequency falls into an internationally protected range for aeronautical navigation, promising little or no interference under all circumstances. The first Block IIF satellite that would provide this signal is set to be launched in 2008.

[edit] Calculating positions

[edit] Using the C/A code

To start off, the receiver picks which C/A codes to listen for by PRN number, based on the almanac information it has previously acquired. As it detects each satellite’s signal, it identifies it by its distinct C/A code pattern, then measures the time delay for each satellite. To do this, the receiver produces an identical C/A sequence using the same seed number as the satellite. By lining up the two sequences, the receiver can measure the delay and calculate the distance to the satellite, called the pseudorange[12].

Overlapping pseudoranges, represented as curves, are modified to yield the probable position

Overlapping pseudoranges, represented as curves, are modified to yield the probable position

Next, the orbital position data, or ephemeris, from the Navigation Message is then downloaded to calculate the satellite’s precise position. A more-sensitive receiver will potentially acquire the ephemeris data quicker than a less-sensitive receiver, especially in a noisy environment.[13] Knowing the position and the distance of a satellite indicates that the receiver is located somewhere on the surface of an imaginary sphere centered on that satellite and whose radius is the distance to it. Receivers can substitute altitude for one satellite, which the GPS receiver translates to a pseudorange measured from the center of the earth.

Locations are calculated not in three-dimensional space, but in four-dimensional spacetime, meaning a measure of the precise time-of-day is very important. The measured pseudoranges from four satellites have already been determined with the receiver’s internal clock, and thus have an unknown amount of clock error. (The clock error or actual time does not matter in the initial pseudorange calculation, because that is based on how much time has passed between reception of each of the signals.[clarify][citation needed]) The four-dimensional point that is equidistant from the pseudoranges is calculated as a guess as to the receiver’s location, and the factor used to adjust those pseudoranges to intersect at that four-dimensional point gives a guess as to the receiver’s clock offset. With each guess, a geometric dilution of precision (GDOP) vector is calculated, based on the relative sky positions of the satellites used. As more satellites are picked up, pseudoranges from more combinations of four satellites can be processed to add more guesses to the location and clock offset. The receiver then determines which combinations to use and how to calculate the estimated position by determining the weighted average of these positions and clock offsets. After the final location and time are calculated, the location is expressed in a specific coordinate system, e.g. latitude/longitude, using the WGS 84 geodetic datum or a local system specific to a country.

[edit] Using the P(Y) code

Calculating a position with the P(Y) signal is generally similar in concept, assuming one can decrypt it. The encryption is essentially a safety mechanism: if a signal can be successfully decrypted, it is reasonable to assume it is a real signal being sent by a GPS satellite.[citation needed] In comparison, civil receivers are highly vulnerable to spoofing since correctly formatted C/A signals can be generated using readily available signal generators. RAIM features do not protect against spoofing, since RAIM only checks the signals from a navigational perspective.

[edit] Accuracy and error sources

The position calculated by a GPS receiver requires the current time, the position of the satellite and the measured delay of the received signal. The position accuracy is primarily dependent on the satellite position and signal delay.

To measure the delay, the receiver compares the bit sequence received from the satellite with an internally generated version. By comparing the rising and trailing edges of the bit transitions, modern electronics can measure signal offset to within about 1% of a bit time, or approximately 10 nanoseconds for the C/A code. Since GPS signals propagate nearly at the speed of light, this represents an error of about 3 meters. This is the minimum error possible using only the GPS C/A signal.

Position accuracy can be improved by using the higher-chiprate P(Y) signal. Assuming the same 1% bit time accuracy, the high frequency P(Y) signal results in an accuracy of about 30 centimeters.

Electronics errors are one of several accuracy-degrading effects outlined in the table below. When taken together, autonomous civilian GPS horizontal position fixes are typically accurate to about 15 meters (50 ft). These effects also reduce the more precise P(Y) code’s accuracy.

Sources of User Equivalent Range Errors (UERE) Source Effect

Ionospheric effects ± 5 meter

Ephemeris errors ± 2.5 meter

Satellite clock errors ± 2 meter

Multipath distortion ± 1 meter

Tropospheric effects ± 0.5 meter

Numerical errors ± 1 meter

[edit] Atmospheric effects

Inconsistencies of atmospheric conditions affect the speed of the GPS signals as they pass through the Earth’s atmosphere and ionosphere. Correcting these errors is a significant challenge to improving GPS position accuracy. These effects are smallest when the satellite is directly overhead and become greater for satellites nearer the horizon since the signal is affected for a longer time. Once the receiver’s approximate location is known, a mathematical model can be used to estimate and compensate for these errors.

Because ionospheric delay affects the speed of microwave signals differently based on frequency—a characteristic known as dispersion—both frequency bands can be used to help reduce this error. Some military and expensive survey-grade civilian receivers compare the different delays in the L1 and L2 frequencies to measure atmospheric dispersion, and apply a more precise correction. This can be done in civilian receivers without decrypting the P(Y) signal carried on L2, by tracking the carrier wave instead of the modulated code. To facilitate this on lower cost receivers, a new civilian code signal on L2, called L2C, was added to the Block IIR-M satellites, which was first launched in 2005. It allows a direct comparison of the L1 and L2 signals using the coded signal instead of the carrier wave.

The effects of the ionosphere generally change slowly, and can be averaged over time. The effects for any particular geographical area can be easily calculated by comparing the GPS-measured position to a known surveyed location. This correction is also valid for other receivers in the same general location. Several systems send this information over radio or other links to allow L1 only receivers to make ionospheric corrections. The ionospheric data are transmitted via satellite in Satellite Based Augmentation Systems such as WAAS, which transmits it on the GPS frequency using a special pseudo-random number (PRN), so only one antenna and receiver are required.

Humidity also causes a variable delay, resulting in errors similar to ionospheric delay, but occurring in the troposphere. This effect is both more localized and changes more quickly than ionospheric effects and is not frequency dependent. These traits making precise measurement and compensation of humidity errors more difficult than ionospheric effects.

Changes in altitude also change the amount of delay due to the signal passing through less of the atmosphere at higher elevations. Since the GPS receiver computes its approximate altitude, this error is relatively simple to correct.

[edit] Multipath effects

GPS signals can also be affected by multipath issues, where the radio signals reflect off surrounding terrain; buildings, canyon walls, hard ground, etc. These delayed signals can cause inaccuracy. A variety of techniques, most notably narrow correlator spacing, have been developed to mitigate multipath errors. For long delay multipath, the receiver itself can recognize the wayward signal and discard it. To address shorter delay multipath from the signal reflecting off the ground, specialized antennas may be used to reduce the signal power as received by the antenna. Short delay reflections are harder to filter out because they interfere with the true signal, causing effects almost indistinguishable from routine fluctuations in atmospheric delay.

Multipath effects are much less severe in moving vehicles. When the GPS antenna is moving, the false solutions using reflected signals quickly fail to converge and only the direct signals result in stable solutions.

[edit] Ephemeris and clock errors

The navigation message from a satellite is sent out only every 30 seconds. In reality, the data contained in these messages tend to be “out of date” by an even larger amount. Consider the case when a GPS satellite is boosted back into a proper orbit; for some time following the maneuver, the receiver’s calculation of the satellite’s position will be incorrect until it receives another ephemeris update. The onboard clocks are extremely accurate, but they do suffer from some clock drift. This problem tends to be very small, but may add up to 2 meters (6 ft) of inaccuracy.

This class of error is more “stable” than ionospheric problems and tends to change over days or weeks rather than minutes. This makes correction fairly simple by sending out a more accurate almanac on a separate channel.

[edit] Selective availability

The GPS includes a feature called Selective Availability (SA) that introduces intentional, slowly changing random errors of up to a hundred meters (328 ft) into the publicly available navigation signals to confound, for example, guiding long range missiles to precise targets. 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.

SA typically added signal errors of up to about 10 meters (32 ft) horizontally and 30 meters (98 ft) vertically. The inaccuracy of the civilian signal was deliberately encoded so as not to change very quickly, for instance the entire eastern U.S. area might read 30 m off, but 30 m off everywhere and in the same direction. To improve the usefulness of GPS for civilian navigation, Differential GPS was used by many civilian GPS receivers to greatly improve accuracy.

During the Gulf War, the shortage of military GPS units and the wide availability of civilian ones among personnel resulted in a decision to disable Selective Availability. This was ironic, as SA had been introduced specifically for these situations, allowing friendly troops to use the signal for accurate navigation, while at the same time denying it to the enemy. But since SA was also denying the same accuracy to thousands of friendly troops, turning it off or setting it to an error of zero meters (effectively the same thing) presented a clear benefit.

In the 1990s, the FAA started pressuring the military to turn off SA permanently. This would save the FAA millions of dollars every year in maintenance of their own radio navigation systems. The military resisted for most of the 1990s, and it ultimately took an executive order to have SA removed from the GPS signal. The amount of error added was “set to zero”[14] at midnight on May 1, 2000 following an announcement by U.S. President Bill Clinton, allowing users access to the error-free L1 signal. Per the directive, the induced error of SA was changed to add no error to the public signals (C/A code). Selective Availability is still a system capability of GPS, and error could, in theory, be reintroduced at any time. In practice, in view of the hazards and costs this would induce for US and foreign shipping, it is unlikely to be reintroduced, and various government agencies, including the FAA,[15] have stated that it is not intended to be reintroduced.

The US military has developed the ability to locally deny GPS (and other navigation services) to hostile forces in a specific area of crisis without affecting the rest of the world or its own military systems.[14]

One interesting side effect of the Selective Availability hardware is the capability to correct the frequency of the GPS caesium and rubidium atomic clocks to an accuracy of approximately 2 × 10-13 (one in five trillion). This represented a significant improvement over the raw accuracy of the clocks.[citation needed]

On 19 September 2007, the United States Department of Defense announced that they would not procure any more satellites capable of implementing SA. [16]

[edit] Relativity

According to the theory of relativity, due to their constant movement and height relative to the Earth-centered inertial reference frame, the clocks on the satellites are affected by their speed (special relativity) as well as their gravitational potential (general relativity). For the GPS satellites, general relativity predicts that the atomic clocks at GPS orbital altitudes will tick more rapidly, by about 45,900 nanoseconds (ns) per day, because they are in a weaker gravitational field than atomic clocks on Earth’s surface. Special relativity predicts that atomic clocks moving at GPS orbital speeds will tick more slowly than stationary ground clocks by about 7,200 ns per day. When combined, the discrepancy is 38 microseconds per day; a difference of 4.465 parts in 1010.[17]. To account for this, the frequency standard onboard each satellite is given a rate offset prior to launch, making it run slightly slower than the desired frequency on Earth; specifically, at 10.22999999543 MHz instead of 10.23 MHz.[18]

GPS observation processing must also compensate for another relativistic effect, the Sagnac effect. The GPS time scale is defined in an inertial system but observations are processed in an Earth-centered, Earth-fixed (co-rotating) system, a system in which simultaneity is not uniquely defined. The Lorentz transformation between the two systems modifies the signal run time, a correction having opposite algebraic signs for satellites in the Eastern and Western celestial hemispheres. Ignoring this effect will produce an east-west error on the order of hundreds of nanoseconds, or tens of meters in position.[19]

The atomic clocks on board the GPS satellites are precisely tuned, making the system a practical engineering application of the scientific theory of relativity in a real-world environment.

[edit] GPS interference and jamming

Since GPS signals at terrestrial receivers tend to be relatively weak, it is easy for other sources of electromagnetic radiation to desensitize the receiver, making acquiring and tracking the satellite signals difficult or impossible.

Solar flares are one such naturally occurring emission with the potential to degrade GPS reception, and their impact can affect reception over the half of the Earth facing the sun. GPS signals can also be interfered with by naturally occurring geomagnetic storms, predominantly found near the poles of the Earth’s magnetic field.[20] Another source of problems is the metal embedded in some car windscreens to prevent icing, degrading reception just inside the car.

Man-made interference can also disrupt, or jam, GPS signals. In one well documented case, an entire harbor was unable to receive GPS signals due to unintentional jamming caused by a malfunctioning TV antenna preamplifier.[21] Intentional jamming is also possible. Generally, stronger signals can interfere with GPS receivers when they are within radio range, or line of sight. In 2002, a detailed description of how to build a short range GPS L1 C/A jammer was published in the online magazine Phrack.[22]

The U.S. government believes that such jammers were used occasionally during the 2001 war in Afghanistan and the U.S. military claimed to destroy a GPS jammer with a GPS-guided bomb during the Iraq War.[23] Such a jammer is relatively easy to detect and locate, making it an attractive target for anti-radiation missiles. The UK Ministry of Defence tested a jamming system in the UK’s West Country on 7 and 8 June 2007. [24]

Some countries allow the use of GPS repeaters to allow for the reception of GPS signals indoors and in obscured locations, however, under EU and UK laws, the use of these is prohibited as the signals can cause interference to other GPS receivers that may receive data from both GPS satellites and the repeater.

Due to the potential for both natural and man-made noise, numerous techniques continue to be developed to deal with the interference. The first is to not rely on GPS as a sole source. According to John Ruley, “IFR pilots should have a fallback plan in case of a GPS malfunction”.[25] Receiver Autonomous Integrity Monitoring (RAIM) is a feature now included in some receivers, which is designed to provide a warning to the user if jamming or another problem is detected. The U.S. military has also deployed their Selective Availability / Anti-Spoofing Module (SAASM) in the Defense Advanced GPS Receiver (DAGR). In demonstration videos, the DAGR is able to detect jamming and maintain its lock on the encrypted GPS signals during interference which causes civilian receivers to lose lock.[26]

[edit] Techniques to improve accuracy

[edit] Augmentation

Main article: GNSS Augmentation

Augmentation methods of improving accuracy rely on external information being integrated into the calculation process. There are many such systems in place and they are generally named or described based on how the GPS sensor receives the information. Some systems transmit additional information about sources of error (such as clock drift, ephemeris, or ionospheric delay), others provide direct measurements of how much the signal was off in the past, while a third group provide additional navigational or vehicle information to be integrated in the calculation process.

Examples of augmentation systems include the Wide Area Augmentation System, Differential GPS, Inertial Navigation Systems and Assisted GPS.

[edit] Precise monitoring

The accuracy of a calculation can also be improved through precise monitoring and measuring of the existing GPS signals in additional or alternate ways.

After SA, which has been turned off, the largest error in GPS is usually the unpredictable delay through the ionosphere. The spacecraft broadcast ionospheric model parameters, but errors remain. This is one reason the GPS spacecraft transmit on at least two frequencies, L1 and L2. Ionospheric delay is a well-defined function of frequency and the total electron content (TEC) along the path, so measuring the arrival time difference between the frequencies determines TEC and thus the precise ionospheric delay at each frequency.

Receivers with decryption keys can decode the P(Y)-code transmitted on both L1 and L2. However, these keys are reserved for the military and “authorized” agencies and are not available to the public. Without keys, it is still possible to use a codeless technique to compare the P(Y) codes on L1 and L2 to gain much of the same error information. However, this technique is slow, so it is currently limited to specialized surveying equipment. In the future, additional civilian codes are expected to be transmitted on the L2 and L5 frequencies (see GPS modernization, below). Then all users will be able to perform dual-frequency measurements and directly compute ionospheric delay errors.

A second form of precise monitoring is called Carrier-Phase Enhancement (CPGPS). The error, which this corrects, arises because the pulse transition of the PRN is not instantaneous, and thus the correlation (satellite-receiver sequence matching) operation is imperfect. The CPGPS approach utilizes the L1 carrier wave, which has a period 1000 times smaller than that of the C/A bit period, to act as an additional clock signal and resolve the uncertainty. The phase difference error in the normal GPS amounts to between 2 and 3 meters (6 to 10 ft) of ambiguity. CPGPS working to within 1% of perfect transition reduces this error to 3 centimeters (1 inch) of ambiguity. By eliminating this source of error, CPGPS coupled with DGPS normally realizes between 20 and 30 centimeters (8 to 12 inches) of absolute accuracy.

Relative Kinematic Positioning (RKP) is another approach for a precise GPS-based positioning system. In this approach, determination of range signal can be resolved to an accuracy of less than 10 centimeters (4 in). This is done by resolving the number of cycles in which the signal is transmitted and received by the receiver. 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).

[edit] GPS time and date

While most clocks are synchronized to Coordinated Universal Time (UTC), the Atomic clocks on the satellites are set to GPS time. The difference is that GPS time is not corrected to match the rotation of the Earth, so it does not contain leap seconds or other corrections which are periodically added to UTC. GPS time was set to match Coordinated Universal Time (UTC) in 1980, but has since diverged. The lack of corrections means that GPS time remains at a constant offset (19 seconds) with International Atomic Time (TAI). Periodic corrections are performed on the on-board clocks to correct relativistic effects and keep them synchronized with ground clocks.

The GPS navigation message includes the difference between GPS time and UTC, which as of 2006 is 14 seconds. Receivers subtract this offset from GPS time to calculate UTC and specific timezone values. New GPS units may not show the correct UTC time until after receiving the UTC offset message. The GPS-UTC offset field can accommodate 255 leap seconds (eight bits) which, at the current rate of change of the Earth’s rotation, is sufficient to last until the year 2330.

As opposed to the year, month, and day format of the Julian calendar, the GPS date is expressed as a week number and a day-of-week number. The week number is transmitted as a ten-bit field in the C/A and P(Y) navigation messages, and so it becomes zero again every 1,024 weeks (19.6 years). GPS week zero started at 00:00:00 UTC (00:00:19 TAI) on January 6, 1980 and the week number became zero again for the first time at 23:59:47 UTC on August 21, 1999 (00:00:19 TAI on August 22, 1999). To determine the current Gregorian date, a GPS receiver must be provided with the approximate date (to within 3,584 days) to correctly translate the GPS date signal. To address this concern the modernized GPS navigation messages use a 13-bit field, which only repeats every 8,192 weeks (157 years), and will not return to zero until near the year 2137.

[edit] GPS modernization

Main article: GPS modernization

Having reached the program’s requirements for Full Operational Capability (FOC) on July 17, 1995,[27] the GPS completed its original design goals. However, additional advances in technology and new demands on the existing system led to the effort to modernize the GPS system. Announcements from the Vice President and the White House in 1998 initiated these changes, and in 2000 the U.S. Congress authorized the effort, referring to it as GPS III.

The project aims to improve the accuracy and availability for all users and involves new ground stations, new satellites, and four additional navigation signals. New civilian signals are called L2C, L5 and L1C; the new military code is called M-Code. Initial Operational Capability (IOC) of the L2C code is expected in 2008.[28] A goal of 2013 has been established for the entire program, with incentives offered to the contractors if they can complete it by 2011.

[edit] Applications

The Global Positioning System, while originally a military project, is considered a dual-use technology, meaning it has significant applications for both the military and the civilian industry.

[edit] Military

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The military use GPS for the following purposes:

[edit] Navigation

GPS allows soldiers to find objectives in the dark or in unfamiliar territory, and to coordinate the movement of troops and supplies.

[edit] Target tracking

Various military weapons systems use GPS to track potential ground and air targets before they are flagged as hostile. These weapons systems pass GPS co-ordinates of targets to precision-guided munitions to allow them to engage the targets accurately.

Military aircraft, particularly those used in air-to-ground roles use GPS to find targets (for example, gun camera video from AH-1 Cobras in Iraq show GPS co-ordinates that can be looked up in Google Earth).

[edit] Missile and projectile guidance

GPS allows accurate targeting of various military weapons including ICBMs, cruise missiles and precision-guided munitions.

Artillery projectiles with embedded GPS receivers able to withstand forces of 12,000G have been developed for use in 155 mm howitzers.[29]

[edit] Search and Rescue

Downed pilots can be located faster if they have a GPS receiver.

[edit] Reconnaissance and Map Creation

The military use GPS extensively to aid mapping and reconnaissance.

[edit] Other

The GPS satellites also carry nuclear detonation detectors, which form a major portion of the United States Nuclear Detonation Detection System.[30]

[edit] Civilian

See also: GPS applications

This antenna is mounted on the roof of a hut containing a scientific experiment needing precise timing.

This antenna is mounted on the roof of a hut containing a scientific experiment needing precise timing.

Many civilian applications benefit from GPS signals, using one or more of three basic components of the GPS; absolute location, relative movement, time transfer.

The ability to determine the receiver’s absolute location allows GPS receivers to perform as a surveying tool or as an aid to navigation. The capacity to determine relative movement enables a receiver to calculate local velocity and orientation, useful in vessels or observations of the Earth. Being able to synchronize clocks to exacting standards enables time transfer, which is critical in large communication and observation systems. An example is CDMA digital cellular. Each base station has a GPS timing receiver to synchronize its spreading codes with other base stations to facilitate inter-cell hand off and support hybrid GPS/CDMA positioning of mobiles for emergency calls and other applications.

Finally, GPS enables researchers to explore the Earth environment including the atmosphere, ionosphere and gravity field. GPS survey equipment has revolutionized tectonics by directly measuring the motion of faults in earthquakes.

To help prevent civilian GPS guidance from being used in an enemy’s military or improvised weaponry, the US Government controls the export of civilian receivers. A US-based manufacturer cannot generally export a GPS receiver unless the receiver contains limits restricting it from functioning when it is simultaneously (1) at an altitude above 18 kilometers (60,000 ft) and (2) traveling at over 515 m/s (1,000 knots).[31]

[edit] History

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The design of GPS is based partly on the similar ground-based radio navigation systems, such as LORAN and the Decca Navigator developed in the early 1940s, and used during World War II. Additional inspiration for the GPS system came when the Soviet Union launched the first Sputnik in 1957. A team of U.S. scientists led by Dr. Richard B. Kershner were monitoring Sputnik’s radio transmissions. They discovered that, because of 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. 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.

The first satellite navigation system, Transit, used by the United States Navy, was first successfully tested in 1960. Using a constellation of five satellites, it could provide a navigational fix approximately once per hour. In 1967, the U.S. Navy developed the Timation satellite which proved the ability to place accurate clocks in space, a technology the GPS system relies upon. In the 1970s, the ground-based Omega Navigation System, based on signal phase comparison, became the first world-wide radio navigation system.

The first experimental Block-I GPS satellite was launched in February 1978.[28] The GPS satellites were initially manufactured by Rockwell International and are now manufactured by Lockheed Martin.

[edit] Timeline

* In 1972, the US Air Force Central Inertial Guidance Test Facility (Holloman AFB) conducted developmental fight tests of two prototype GPS receivers over White Sands Missile Range, using ground-based pseudo-satellites.

* In 1978 the first experimental Block-I GPS satellite was launched.

* In 1983, after Soviet interceptor aircraft shot down the civilian airliner KAL 007 in restricted Soviet airspace, killing all 269 people on board, U.S. President Ronald Reagan announced that the GPS system would be made available for civilian uses once it was completed.

* By 1985, ten more experimental Block-I satellites had been launched to validate the concept.

* On February 14, 1989, the first modern Block-II satellite was launched.

* In 1992, the 2nd Space Wing, which originally managed the system, was de-activated and replaced by the 50th Space Wing.

* By December 1993 the GPS system achieved initial operational capability[32]

* By January 17, 1994 a complete constellation of 24 satellites was in orbit.

* Full Operational Capability was declared by NAVSTAR in April 1995.

* In 1996, recognizing the importance of GPS to civilian users as well as military users, U.S. President Bill Clinton issued a policy directive[33] declaring GPS to be a dual-use system and establishing an Interagency GPS Executive Board to manage it as a national asset.

* In 1998, U.S. Vice President Al Gore announced plans to upgrade GPS with two new civilian signals for enhanced user accuracy and reliability, particularly with respect to aviation safety.

* On May 2, 2000 “Selective Availability” was discontinued as a result of the 1996 executive order, allowing users to receive a non-degraded signal globally.

* In 2004, the United States Government signed a historic agreement with the European Community establishing cooperation related to GPS and Europe’s planned Galileo system.

* In 2004, U.S. President George W. Bush updated the national policy, replacing the executive board with the National Space-Based Positioning, Navigation, and Timing Executive Committee.

* November 2004, QUALCOMM announced successful tests of Assisted-GPS system for mobile phones.[3]

* In 2005, the first modernized GPS satellite was launched and began transmitting a second civilian signal (L2C) for enhanced user performance.

* The most recent launch was on 17 November 2006. The oldest GPS satellite still in operation was launched in August 1991.

* On September 14, 2007, the aging mainframe-based Ground Segment Control System was transitioned to the new Architecture Evolution Plan. [4]

[edit] Satellite numbers

Name Launch Period No of satellites launched, inc. launch failures Currently in service

Block I 1978-1985 11 0

Block II 1985-1990 9 0

Block IIA 1990-1997 19 15+11

Block IIR 1997-2004 12 12

Block IIR-M 2005- 3 3

Total 54 (plus one not launched) 30+1

1One test satellite

[edit] Awards

Two GPS developers have received the National Academy of Engineering Charles Stark Draper prize year 2003:

* 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).

* Bradford Parkinson, professor of aeronautics and astronautics at Stanford University, conceived the present satellite-based system in the early 1960s and developed it in conjunction with the U.S. Air Force.

One GPS developer, Roger L. Easton, received the National Medal of Technology on February 13, 2006 at the White House.[34]

On February 10, 1993, the National Aeronautic Association selected the Global Positioning System Team as winners of the 1992 Robert J. Collier Trophy, the most prestigious aviation award in the United States. This team consists of researchers from the Naval Research Laboratory, the U.S. Air Force, the Aerospace Corporation, Rockwell International Corporation, and IBM Federal Systems Company. 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.”

[edit] Other systems

Main article: Global Navigation Satellite System

Other satellite navigation systems in use or various states of development include:

* Beidou — China’s regional system that China has proposed to expand into a global system named COMPASS.

* Galileo — a proposed global system being developed by the European Union, joined by China, Israel, India, Morocco, Saudi Arabia and South Korea, Ukraine planned to be operational by 2011–12.

* GLONASS — Russia’s global system which is being restored to full availability in partnership with India.

* Indian Regional Navigational Satellite System (IRNSS) — India’s proposed regional system.

* QZSS – Japanese proposed regional system, adding better coverage to the Japanese islands.

[edit] See also

Satellite navigation systems Portal

Nautical Portal

* RAIM

* SIGI

* radio navigation

* High Sensitivity GPS

* Degree Confluence Project Use GPS to visit integral degrees of latitude and longitude.

* Exif, GPS data transfer.

* Geotagging

* Geocaching

* NaviTraveler.com, – a GPS point sharing community.

* GPS Drawing Digital mapping and drawing with GPS tracks.

* GPS tracking

* GPS/INS

* Assisted GPS

* GPX (XML schema for interchange of waypoints)

* ID Sniper rifle

* OpenStreetMap, free content maps and street pictures (GFDL)

* Telematics: Many telematics devices use GPS to determine the location of mobile equipment.

* The American Practical Navigator—Chapter 11 “Satellite Navigation”

* Point of Interest

* Automotive navigation system

* NextGen

[edit] Notes

1. ^ Parkinson, B.W. (1996), Global Positioning System: Theory and Applications, chap. 1: Introduction and Heritage of NAVSTAR, the Global Positioning System. pp. 3-28, American Institute of Aeronautics and Astronautics, Washington, D.C.

2. ^ a b GPS Overview from the NAVSTAR Joint Program Office. Accessed December 15, 2006.

3. ^ HowStuffWorks. How GPS Receivers Work. Accessed May 14, 2006.

4. ^ globalsecurity.org [1].

5. ^ Dana, Peter H. GPS Orbital Planes. August 8, 1996.

6. ^ What the Global Positioning System Tells Us about Relativity. Accessed January 2, 2007.

7. ^ USCG Navcen: GPS Frequently Asked Questions. Accessed January 3, 2007.

8. ^ Massatt, Paul and Brady, Wayne. “Optimizing performance through constellation management”, Crosslink, Summer 2002, pages 17-21.

9. ^ US Coast Guard General GPS News 9-9-05

10. ^ USNO. NAVSTAR Global Positioning System. Accessed May 14, 2006.

11. ^ NMEA NMEA 2000

12. ^ http://gge.unb.ca/Resources/HowDoesGPSWork.html

13. ^ AN02 Network Assistance (HTML). Retrieved on 2007-09-10.

14. ^ a b Office of Science and Technology Policy. Presidential statement to stop degrading GPS. May 1, 2000.

15. ^ FAA, Selective Availability. Retrieved Jan. 6, 2007.

16. ^ http://www.defenselink.mil/releases/release.aspx?releaseid=11335

17. ^ Rizos, Chris. University of New South Wales. GPS Satellite Signals. 1999.

18. ^ The Global Positioning System by Robert A. Nelson Via Satellite, November 1999

19. ^ Ashby, Neil Relativity and GPS. Physics Today, May 2002.

20. ^ Space Environment Center. SEC Navigation Systems GPS Page. August 26, 1996.

21. ^ The hunt for an unintentional GPS jammer. GPS World. January 1, 2003.

22. ^ Low Cost and Portable GPS Jammer. Phrack issue 0x3c (60), article 13]. Published December 28, 2002.

23. ^ American Forces Press Service. CENTCOM charts progress. March 25, 2003.

24. ^ [2]

25. ^ Ruley, John. AVweb. GPS jamming. February 12, 2003.

26. ^ Commercial GPS Receivers: Facts for the Warfighter. Hosted at the Joint Chiefs website, linked by the USAF’s GPS Wing DAGR program website. Accessed on 10 April, 2007

27. ^ US Coast Guard news release. Global Positioning System Fully Operational

28. ^ a b Hydrographic Society Journal. Developments in Global Navigation Satellite Systems. Issue #104, April 2002. Accessed April 5, 2007.

29. ^ XM982 Excalibur Precision Guided Extended Range Artillery Projectile. GlobalSecurity.org (2007-05-29). Retrieved on 2007-09-26.

30. ^ Sandia National Laboratory’s Nonproliferation programs and arms control technology.

31. ^ Arms Control Association. Missile Technology Control Regime. Accessed May 17, 2006.

32. ^ United States Department of Defense. Announcement of Initial Operational Capability. December 8, 1993.

33. ^ National Archives and Records Administration. U.S. GLOBAL POSITIONING SYSTEM POLICY. March 29, 1996.

34. ^ United States Naval Research Laboratory. National Medal of Technology for GPS. November 21, 2005

[edit] External links

Wikimedia Commons has media related to:

Global Positioning System

Government links

* GPS.gov—General public education website created by the U.S. Government

* National Space-Based PNT Executive Committee—Established in 2004 to oversee management of GPS and GPS augmentations at a national level.

* USCG Navigation Center—Status of the GPS constellation, government policy, and links to other references. Also includes satellite almanac data.

* The GPS Joint Program Office (GPS JPO)—Responsible for designing and acquiring the system on behalf of the US Government.

* U.S. Naval Observatory’s GPS constellation status

* U.S. Army Corps of Engineers manual: NAVSTAR HTML and PDF (22.6 MB, 328 pages)

* PNT Selective Availability Announcements

* GPS SPS Signal Specification, 2nd Edition—The official Standard Positioning Signal specification.

* Federal Aviation Administration’s GPS FAQ

Introductory / tutorial links

* How does GPS work? TomTom explains GPS, navigation, and digital maps

* GPS Academy Garmin interactive video web site explaing what exactly GPS is and what it can do for you

* HowStuffWorks’ Simplified explanation of GPS and video about how GPS works.

* Trimble’s Online GPS Tutorial Tutorial designed to introduce you to the principles behind GPS

* GPS and GLONASS Simulation(Java applet) Simulation and graphical depiction of space vehicle motion including computation of dilution of precision (DOP)

Technical, historical, and ancillary topics links

* Dana, Peter H. “Global Positioning System Overview”

* Satellite Navigation: GPS & Galileo (PDF)—16-page paper about the history and working of GPS, touching on the upcoming Galileo

* History of GPS, including information about each satellite’s configuration and launch.

* Chadha, Kanwar. “The Global Positioning System: Challenges in Bringing GPS to Mainstream Consumers” Technical Article (1998)

* GPS Weapon Guidance Techniques

* RAND history of the GPS system (PDF)

* GPS Anti-Jam Protection Techniques

* Crosslink Summer 2002 issue by The Aerospace Corporation on satellite navigation.

* Improved weather predictions from COSMIC GPS satellite signal occultation data.

* David L. Wilson’s GPS Accuracy Web Page A thorough analysis of the accuracy of GPS.

* Innovation: Spacecraft Navigator, Autonomous GPS Positioning at High Earth Orbits Example of GPS receiver designed for high altitude spaceflight.

* The Navigator GPS Receiver GSFC’s Navigator spaceflight receiver.

* Neil Ashby’s Relativity in the Global Positioning System

[show]

v • d • e

Satellite navigation systems

Historical Flag of the United States Transit

Operational Flag of the Soviet Union / Flag of Russia GLONASS · Flag of the United States GPS

Developmental Flag of the People’s Republic of China Beidou/COMPASS · Flag of Europe Galileo · Flag of India IRNSS · Flag of Japan QZSS

Related topics EGNOS · GAGAN · GPS·C · LAAS · MSAS · WAAS

[show]

v • d • e

Time signal stations

Longwave DCF77 · HBG · JJY · MSF · TDF · WWVB

Shortwave BPM · CHU · RWM · WWV · WWVH · YVTO

GNSS time transfer Beidou · Galileo · GLONASS · GPS · IRNSS

Defunct time stations OMA · VNG

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v • d • e

Global structure in Systems, Systems sciences and Systems scientists

Categories Category:Conceptual systems · Category:Physical systems · Category:Social systems · Category:Systems · Category:Systems science · Category:Systems scientists · Category:Systems theory

Systems Biological system · Complex system · Complex adaptive system · Conceptual system · Cultural system · Dynamical system · Economic system · Ecosystem · Formal system · Global Positioning System · Human organ systems · Information systems · Legal system · Metric system · Nervous system · Non-linear system · Operating system · Physical system · Political system · Sensory system · Social system · Solar System · System · Systems of measurement

Fields of theory Chaos theory · Complex systems · Control theory · Cybernetics · Holism in science · Sociotechnical systems theory · Systems biology · System dynamics · Systems ecology · Systems engineering · Systems theory · Systems science

Systems scientists Russell L. Ackoff · William Ross Ashby · Gregory Bateson · Ludwig von Bertalanffy · Kenneth E. Boulding · Peter Checkland · C. West Churchman · Heinz von Foerster · Charles François · Jay Wright Forrester · Ralph W. Gerard · Debora Hammond · George Klir · Niklas Luhmann · Humberto Maturana · Donella Meadows · Mihajlo D. Mesarovic · Howard T. Odum · Talcott Parsons · Ilya Prigogine · Anatol Rapoport · Francisco Varela · John N. Warfield · Norbert Wiener

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