The Global Positioning System (GPS) is a global navigation satellite system (GNSS) developed by the United States Department of Defense and managed by the United States Air Force 50th Space Wing. It is the only fully functional GNSS in the world, can be used freely, and is often used by civilians for navigation purposes. It uses a constellation of between 24 and 32 Medium Earth Orbit satellites that transmit precise microwave signals, which allow GPS receivers to determine their current location, the time, and their velocity. Its official name is NAVSTAR GPS. Although NAVSTAR is not an acronym, a few backronyms have been created for it.
Since it became fully operational in 1993, GPS has become a widely used aid to navigation worldwide, and a useful tool for map-making, land surveying, commerce, scientific uses, and hobbies such as geocaching. Also, the precise time reference is used in many applications including the scientific study of earthquakes. GPS is also a required key synchronization resource of cellular networks, such as the Qualcomm CDMA air interface used by many wireless carriers in a multitude of countries.
GPS is a complex technology but understanding it can be quite easy if you take it one step at a time. The Global Positioning System (GPS) is a worldwide radio-navigation system formed from a constellation of 24 satellites and their ground stations.
Timeline
* In 1972, the US Air Force Central Inertial Guidance Test Facility (Holloman AFB) conducted developmental flight 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 that strayed into prohibited airspace due to navigational errors, killing all 269 people on board, U.S. President Ronald Reagan announced that the GPS 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 achieved initial operational capability.
* 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[9] 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 for mobile phones.
* In 2005, the first modernized GPS satellite was launched and began transmitting a second civilian signal (L2C) for enhanced user performance.
* On September 14, 2007, the aging mainframe-based Ground Segment Control System was transitioned to the new Architecture Evolution Plan.
* The most recent launch was on March 15, 2008.[12] The oldest GPS satellite still in operation was launched on November 26, 1990, and became operational on December 10, 1990.
(source: wikipedia)
GPS uses these "man-made stars" as reference points to calculate positions accurate to a matter of meters. In fact, with advanced forms of GPS you can make measurements to better than a centimeter! In a sense it's like giving every square meter on the planet a unique address. GPS receivers have been miniaturized to just a few integrated circuits and so are becoming very economical. And that makes the technology accessible to virtually everyone. These days GPS is finding its way into cars, boats, planes, construction equipment, movie making gear, farm machinery, even laptop computers. Soon GPS will become almost as basic as the telephone. Indeed, at Trimble, we think it just may become a universal utility
Here's how GPS works in five logical steps:
1. The basis of GPS is "triangulation" from satellites. We're using the word "triangulation" very loosely here because it's a word most people can understand, but purists would not call what GPS does "triangulation" because no angles are involved. It's really "trilateration." Trilateration is a method of determining the relative positions of objects using the geometry of triangles.
2. To "triangulate," a GPS receiver measures distance using the travel time of radio signals.
3. To measure travel time, GPS needs very accurate timing which it achieves with some tricks.
4. Along with distance, you need to know exactly where the satellites are in space. High orbits and careful monitoring are the secret.
5. Finally you must correct for any delays the signal experiences as it travels through the atmosphere.
Using GPS
You have to buy a GPS device to use it. But if you hve one you can still use GPS with any built-in phone GPS sytem. Nokia has brought GPS with a big bang by integrating the GPS function into its top of the line mobiles. But I have seen a lot of guys being unable to make full use of the service due to limited knowledge about it.
Lets see the steps in order that will enable you to use GPS to its full potential.
Step 1: Install the latest firmware of your mobile
Having the latest firmware on your mobile never hurts and is always recommended. It also improves the GPS/A-GPS performance on your mobile as in new firmware bugs get ironed out which improve performance and reliability of the applications and the phone in general.Download and install the latest firmware of your phone using the Nokia Software Updater(NSU) which will hardly take 10-15 minutes depending on your broadband connection speed.
Step 2: Download latest version of Nokia Maps Loader
Download the latest version of Nokia Maps loader from Nokia Maps.The latest version will have new features and will be faster and less buggier than the previous version, so its highly recommended to install the latest version.
Currently the latest version of Nokia Maps Loader is v1.3 but new versions are released from time to time by Nokia which bring in changes that boost the capability of the application. So even after installing you should periodically check for new versions.
Step 3: Download the Maps you need
In order to use the GPS functionality, you need to have the maps of the location you want to view. After installing the Nokia Maps application on your phone, run the application once. This will create a folder in which you can put the maps which you can download on your PC and put into the memory card by using the data cable.
Step 4: Configure Nokia Maps application
You need to configure the Nokia Maps application for it to work properly. You have to firstly define an access point that the application will use to connect. If you have access to unlimited GPRS/HSPDA plan then select that in access point. The connection is used to download maps if required, extra information on maps, voice navigation,address searches etc. You can also set some variousStep 5: Enable Assisted GPS (A-GPS)
A-GPS helps you in navigating through maps but requires 3G/EDGE/GPRS connection to operate. You have to tick the option in settings to enable Assisted GPS. With A-GPS you can navigate even in those places that have weak GPS signals and get detailing in maps. Also you get voice navigation that assists you while driving by telling you when and where to take turns.
GPS on mobile phones is all set to take off in a big way and the major deterrent seems to be that very few detailed maps are available that makes GPS useless for many people. But nevertheless they are increasing day by day and hence expanding the database of GPS users.
PerformanceWe tested the Nokia 500 Auto Navigation in San Francisco, and from a cold start, it took the unit about three minutes to get a fix on our location under cloudy skies, while subsequent starts took anywhere from a few seconds to a minute.
The receiver did a good job of tracking our position as we drove throughout the city. It did lose its lock when we drove through the Broadway Tunnel, but it was able to pick up a signal soon after we exited the tunnel.
We used the Nokia 500 on two trips. On the first journey, we plotted a course from the Marina District of San Francisco to Sunnyvale, California. We punched in our start and end points, and the system was pretty quick to calculate directions. Having never been to this destination, we took the Nokia 500 for its word and set out on our trip.
We're happy to report that it got us there efficiently and without any problems. We also tested our standard route from the Marina to CNET's downtown headquarters, and again, no major problems. We missed several turns to test the route recalculation rate, which was fast enough to get us back on course. All that said, we have to say the text-to-speech directions were pretty bad. The voice sounded very robotic and while we understood what it was saying, it mangled quite a few street names.
We paired the Nokia 500 with the RIM BlackBerry Curve 8330 for Verizon Wireless and had no problems connecting or downloading the phone's contact list. We were also able to make and receive calls.
If you're interested in the multimedia experience (you know how I feel about GPS and multimedia), music playback sounded a bit blown out through the system's speakers, though you can plug in a pair of headphones or stream it through your car stereo via FM transmitter.
Usign GPS with iPhone
Find your location, get directions, and see traffic — all from your phone. Maps on iPhone 3G combines GPS, Wi-Fi, and cell tower location technology with the Multi-Touch interface to create the best mobile map application ever.
Find yourself.
iPhone 3G finds your location via GPS or by triangulating your position using Wi-Fi and cellular towers. Drop a pin to mark your location, bookmark it, or share it with others via email. iPhone 3G also finds points of interest by keyword: Search for “coffee” and iPhone shows you every cafe nearby. Learn more
Enjoy the view.
Just like Google Maps on your computer, Google Maps on iPhone lets you switch between views of map data, satellite images, hybrid view, or street view. Multi-Touch makes the difference. Tap to zoom, pan, and change your view on the move.
Get directions.
Get directions to wherever from wherever. View a list of turn-by-turn directions or follow a highlighted map route and track your progress with live GPS tracking.
See traffic.
Maps on iPhone shows you live traffic information, indicating traffic speed along your route in easy-to-read green, red, and yellow highlights.
How to Use GPS on an iPhone 3G
Other systems
Other satellite navigation systems in use or various states of development include:
* Flag of the People's Republic of China Beidou – China's regional system that China has proposed to expand into a global system named COMPASS.
* Flag of Europe Galileo – a proposed global system being developed by the European Union, joined by China, Israel, India, Morocco, Saudi Arabia, South Korea, and Ukraine, planned to be operational by 2013.
* Flag of Russia GLONASS – Russia's global system which is being restored to full availability in partnership with India.
* Flag of India Indian Regional Navigational Satellite System (IRNSS) – India's proposed regional system.
* Flag of Japan QZSS – Japanese proposed regional system, adding better coverage to the Japanese Islands.