 - The GPS (Global Positioning System) is a "constellation" of 24 well-spaced satellites that orbit the Earth and make it possible for people with ground receivers to pinpoint their geographic location. The location accuracy is anywhere from 100 to 10 meters for most equipment. Accuracy can be pinpointed to within one (1) meter with special military-approved equipment. GPS equipment is widely used in science and has now become sufficiently low-cost so that almost anyone can own a GPS receiver.The GPS is owned and operated by the U.S. Department of Defense but is available for general use around the world. Briefly, here's how it works: - 21 GPS satellites and three spare satellites are in orbit at 10,600 miles above the Earth. The satellites are spaced so that from any point on Earth, four satellites will be above the horizon.
- Each satellite contains a computer, an atomic clock, and a radio. With an understanding of its own orbit and the clock, it continually broadcasts its changing position and time. (Once a day, each satellite checks its own sense of time and position with a ground station and makes any minor correction.)
- On the ground, any GPS receiver contains a computer that "triangulates" its own position by getting bearings from three of the four satellites. The result is provided in the form of a geographic position - longitude and latitude - to, for most receivers, within 100 meters.
- If the receiver is also equipped with a display screen that shows a map, the position can be shown on the map.
- If a fourth satellite can be received, the receiver/computer can figure out the altitude as well as the geographic position.
- If you are moving, your receiver may also be able to calculate your speed and direction of travel and give you estimated times of arrival to specified destinations.
The GPS is being used in science to provide data that has never been available before in the quantity and degree of accuracy that the GPS makes possible. Scientists are using the GPS to measure the movement of the arctic ice sheets, the Earth's tectonic plates, and volcanic activity. GPS receivers are becoming consumer products. In addition to their outdoor use (hiking, cross-country skiing, ballooning, flying, and sailing), receivers can be used in cars to relate the driver's location with traffic and weather information. Here are some Web locations that describe GPS receiver products:
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Learn more about WiMAX, 3G and Wireless Broadband |
| WiMAX tutorial: This tutorial explains WiMAX technology, applications and terminology. It also provides an overview of WiMAX services, performance, security and devices. |
| 1G, 2G, 3G, 4G: 3G wireless overview and history lesson. |
| Definitions: CDMA, TDMA and GSM: Definitions: CDMA, TDMA and GSM |
| 3G wireless: The long and winding road: In this tip, Lisa Phifer sorts out the cellular alphabet soup and looks at the complex history behind today's 3G wireless. |
| Mobile and Wireless Protocols: This Mobile and Wireless Protocols Guide explains the various mobile protocols and offers tips and advice for selecting and using them in your organization. |
| WiMax or LTE: Which is the future of wireless?: 4G wireless vendors are developing a competitive marketplace for the future by choosing two different technologies -- WiMax and LTE. |
| Using 3G phones for laptop Internet access: Learn how to use a 3G phone for laptop Internet access. |
| CDMA2000: A 3G mobile technology: CDMA2000 is a 3G mobile technology that includes 1xRTT, EV-DO Rev 0, EV-DO Rev A and EV-DO Rev B, and it competes with GSM technologies. |
| CDMA technology: An understanding of CDMA technology is critical for mobile managers when they are trying to select the best cellular solution for their enterprise mobile strategy. |
| Mobile Radio Systems: This chapter is an intro to the various mobile radio systems. It provides a foundation for comparing competing mobile radio access systems for supporting mobile broadband services. |
| WiMAX tutorial: This tutorial explains WiMAX technology, applications and terminology. It also provides an overview of WiMAX services, performance, security and devices. |
| Smartphone user review: Apple iPhone 3G: After much anticipation, Apple released its updated iPhone on Friday, offering a device that operates on a 3G network. |
| CONTRIBUTORS: |
Moshe Peleg |
| LAST UPDATED: |
17 Oct 2008
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