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How the Global Positioning System GPS Works(Part 1)

When people talk about "a GPS," they usually mean a GPS

receiver. The GPS is in a little gadget you carry around or your cell phone or computer. But that is

not what GSP.

The Global Positioning System (GPS) actually is a nework of 27 Earth-orbiting satellites that surrond

the earth like a belt. The U.S. military developed and implemented this satellite network as a military

navigation system, but soon opened it up to everybody else.

Each of these 3,000- to 4,000-pound solar-powered satellites circles the globe at about 12,000 miles

(19,300 km), making two complete rotations every day. The orbits are arranged so that at any time,

anywhere on Earth, there are at least four satellites "visible" in the sky.,

A GPS receiver's job is to locate four or more of these satellites, figure out the distance to each, and

use this information to deduce its own location. So the satellite is parked in a special orbit which

keeps the satellite stationary with regard to a location on the earth's surface.

This operation is based on a simple mathematical principle called trilateration.GPS receiver

calculates its position on earth based on the information it receives from four located satellites. This

system works pretty well, but inaccuracies do pop up. For one thing, this method assumes the radio

signals will make their way through the atmosphere at a consistent speed (the speed of light). In fact,

the Earth's atmosphere slows the electromagnetic energy down somewhat, particularly as it goes

through the ionosphere and troposphere. The delay varies depending on where you are on Earth,

which means it's difficult to accurately factor this into the distance calculations.

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The Practical Uses of Global PositioningSystems (GPS)These are some of the ways that GPS is used in the "real world" for a variety of different purposes.

In this lens we feature the "best of the breed" products in these GPS use categories

1. GeoCaching: High Tech Treasure Hunting: Geocaching takes treasure hunting one step

further by using GPS units to located hidden treasures. The name of the game is a

combination of "Geo" from geography and "Caching" from the action of hiding the cache (or

treasure). The term cache is commonly used among hikers and campers to refer to a hidden

supply of food or other provisions.

2. Personal Emergencies: GPS equipped cell phones can transmit precise locations to 911

dispatchers. This allows the dispatcher to have an immediate and accurate location instead

of relying upon descriptions of people who may be unfamiliar with the area or too distraught

to explain their location. The same technology has also helped catch people who make crank

911 calls from their GPS-enabled cell phone.

3. Recreational Uses: GPS is popular among hikers, hunters, snowmobilers, mountain bikers,

and cross-country skiers. rails can be viewed on topographic map software, traced on the

screen and that route can be downloaded into the GPS. Then, in the field the route can be

displayed in the map window of the GPS and easily followed. Another use is to leave theGPS on and in a mesh pocket of your backpack while hiking. This will allow the GPS to

record a tracklog of your hike. The tracklog can be shared with others, plotted on maps, used

for distance hiked estmiates and even printed with mapping software and shared with friends

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4. Emergency Roadside Assistance 

OnStar by GM for example uses GPS to track vehicles' whereabouts and allows motorists to

summon emergency help or to ask directions.

5. Tracking Your Kids: GPS-enabled cell phones can be used to monitor your kids. When

Johnny calls you for his after school check in you can confirm if his coordinates are at the

public library or at the pool ha

6. Photography: Geocoding Photos Some cameras will annotate your digital and traditional

images with the date and time, however, new GPS-enabled cameras can also annotate them

with precision coordinates which mark the location of your photos. These annotations can be

very useful in science field work, real estate, law enforcement and many other areas.

7. Automobiles and Driving: GPS tracking devices can be used to navigate your car through

traffic and find your way to any destination. Many Auto GPS Systems come with preloaded

destination settings or points of interest (POI) that provide directions to attractions, and

important pit stops such as gas stations, hotels, motels, and lodges. For vacation travel, or

any other time you need to map out a course for traveling, the system has course-planning

functionality.

8. Laptop GPS: Laptop GPS receivers turn any mobile computer into a fully functional GPS

System. Save money and use a laptop GPS receiver for in-vehicle, office based meetings to

track locations and find directions or simply to plan a cycle ride for the next day. The in built

sophistication of the laptop, augmented with navigation and mapping programs provides

much more extensive information than most handheld applications. By using laptop GPS

navigation, you are using an already familiar tool, with no need to learn new hardware

functionality. Laptop GPS receivers are simply attached to your laptop, notebook or

utlrasmall computer using USB or serial connections as with many other peripheral devices.

Quite often bundled with software, they are very effective GPS systems

You know where you want to go, and Microsoft Streets & Trips 2011 with GPS can help you get

there. This best-selling travel and map software has been enhanced with several new features that

take all the guesswork out of traveling, letting you focus on the sites, instead of the directions. With

more than 1.6 million points of interest to choose from, and with updated maps and the most

extensive trip planning features you'll find anywhere, Streets & Trips will help you plan your trip, your

way. This package of software and GPS Locator is the ultimate travel tool for anyone who wants to

plan a memorable vacation, or simply needs to find their way around town without a hitch.

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It starts with all the door-to-door routing, location-finding and comprehensive mapping power of

Microsoft Streets and Trips, and adds a plug-and-play Global Positioning System (GPS) locator that

helps you stay on track and always knows where your next turn is. Combining the power and

versatility of a GPS receiver with mapping information that is pinpoint accurate and easy-to-use,

Streets & Trips 2011 with GPS Locator is the essential travel tool.

The Global Positioning System Web Def

Developed by the USit 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. These costs

are funded by the US and GPS is free for civilian use as a public good

How the Global Positioning System PinpointsYour Location

All of your devices and gadgets which you know as having a GPS are actually receivers that hook

into the Global Positioning System (GPS). The GPS is a network of of 27 Earth-orbiting satellites.

Developed first for the US miliary and implemented as a military navigation system, but soon opened

it up for commercial uses which has become extensive.

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Each of the the two ton solar-powered satellites circles the globe at about 12,000 miles , making two

complete rotations every day. The orbits are arranged so that at anywhere on Earth, there are at

least four satellites "visible" in the sky at all times.

The GPS receiver in your device locates four or more of system's satellites, figure out the distance to

each, and use this information to deduce its own location using the mathematical principle called

trilateration.

Based on this information, the Global Positioning System can pinpoint your location, anywhere in the

world!

How a GPS Works Part 2

Some of the problems with the accuracy of the GPS: 

Problems with the accurarcy of the Global Postiting System' in pinpoining an also occur when radio

signals bounce off large objects, such as skyscrapers, giving a receiver the impression that asatellite is farther away than it actually is. On top of all that, satellites sometimes just send out bad

almanac data, misreporting their own position.

Differential GPS (DGPS) helps correct these errors. The basic idea is to gauge GPS inaccuracy at a

stationary receiver station with a known location. Since the DGPS hardware at the station already

knows its own position, it can easily calculate its receiver's inaccuracy. The station then broadcasts a

radio signal to all DGPS-equipped receivers in the area, providing signal correction information for

that area. In general, access to this correction information makes DGPS receivers much more

accurate than ordinary receivers.

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GPS Locators were a true technological breakthrough. Using the power of satellites, they can

pinpoint your location on the planet within inches.