The process by which all these components interact to provide location information is simple in theory but complex in reality. The basis of the GPS system in locating a receiver is a technique called triangulation. In triangulation, a receiver measures the distance from itself anywhere on earth to each of three satellites in the GPS system. In order to triangulate, it first measures the distance to the first satellite and recognizes that it must be located on the surface of a sphere. The sphere’s center must therefore be located a... ... middle of paper ... ...roaming receivers use the transmitted time differentials for the satellites they are measuring to perform the calculations and therefore have the ability to determine positions more accurately.
In this orbit, each satellite makes two complete rotations around the planet everyday and the orbits are arranged so that at any time, there are at least four satellites visible in the sky, anywhere on the planet. The GPS receiver unit on the ground, locates these satellites and figures out the distance to each satellite, and then uses that information to figure out its own location. This process is called trilateration[i]. Trilateration is a little tricky to explain in 3-dime... ... middle of paper ... ...tuff Works, 14 Nov. 2003, <http://electronics.howstuffworks.com/gps.htm>. [ii] Steven Ashley, “Next Generation GPS,” Scientific American, September 2003: 34.
GPS is the only system available today that will tell someone their exact position on Earth at any given time in any type of weather. There are 24 satellites in all, which orbit about 11,000 nautical miles above the earth. The satellites are monitored by ground stations located around the world and can transmit signals that can be detected by anyone with a GPS receiver. Using this receiver you can determine your position on Earth with great accuracy. GPS satellites consist of 3 segments: space, control and user.
2. Space The space part is the NAVigation Satellite Timing And Ranging (NAVSTAR) group of satellites that bradcast the GPS signals. There are 24 satellites orbiting at about 20,200km above the Earth. They each make one revolution approximately every 12 hours. 3.
The Global Positioning System (GPS) is a burgeoning technology, which provides unequalled accuracy and flexibility of positioning for navigation, surveying and GIS data capture. The GPS NAVSTAR (Navigation Satellite timing and Ranging Global Positioning System) is a satellite-based navigation, timing and positioning system. The GPS provides continuous three-dimensional positioning 24 hrs a day throughout the world. The technology seems to be beneficiary to the GPS user community in terms of obtaining accurate data up to about100 meters for navigation, meter-level for mapping, and down to millimetre level for geodetic positioning. The GPS technology has tremendous amount of applications in GIS data collection, surveying, and mapping.
GPS needs at least 24 satellites to provide full coverage of every point on the earth, all the time. To calculate one position on the earth, at least 3 satellites are needed. Currently, there are 28 working GPS satellites, out of roughly 750 currently in miliary, civilian and commercial use. GPS satellites, quite simply, broadcast data - each satellite knows two things: its exact location in obit, and exactly what time it is. It knows its position within a few feet, whilst moving a t 17 000 miles per hour, and knows the time within approximately 100 picoseconds (1 trillion picoseconds to a second).
Ball Aerospace and Technologies Corporation is a leading provider of Aerospace hardware. They specialize in the design and development in imaging and precision attitude control. Ball Aerospace and DigitalGlobe have been working together since the mid 90’s and Ball has been a key partner in meeting the increased demand for earth imaging and enhancing the geospatial information market. With the success of QuickBird, which was launched in 2001, images as small as 2 feet can be identified. Because of this, the two Companies merged their technologies and started working towards higher resolution capabilities in the aerospace industry.
GPS uses twenty-six satellites and ground tracking stations around the world to compute distances using time. This is done by finding the difference between the time a signal is sent and the time it is received. The satellites have atomic clocks so the time is extremely accurate. The receivers position is determined by using three satellites, this is called triangulation.(kAPLAN,eLLIOTT. UNDERSTANDING GPS:PRINCPLES AND APPLICATIONS) GPS is made up of three segments: space, control
By the middle of 1961, RCA had a contract with NASA to build, a 4000 mile high, medium-orbit, active communications satellite called RELAY, AT&T was working on its own medium-orbit satellite called TELSTAR, and Hughes Aircraft Company had an exclusive contract to build a 24-hour orbit, 20,000 mile high satellite, called SYNCOM. By 1964, two TELSTARs, two RELAYs, and two SYNCOMs had operated successfully in space. The transponder technology used by AT&T in the TELSTAR I satellite is current technology in use today (Whalen, n.d.). On April 6, 1965, a new company called COMSAT launched its first satellite, EARLY BIRD, from Cape Canaveral beginning Global satellite communications. The EARLY BIRD satellite provided almost 10 times the capacity of submarine telephone cables for almost 1/10th the price.
On 6 December 1997, a mile-wide asteroid was discovered by astronomer Jim Scotti, a member in the University of Arizona's Spacewatch group. He used a 77-year-old telescope along with an electric camera that caught the asteroid on film. He then used a computer specially programmed to look for objects moving against the background of fixed stars. The computer worked so well that Scotti described the asteroid as "sticking out like a sore thumb" (Jaroff 68). His information was relayed to Brian Marsden, a Harvard astronomer, to determine the course of the asteroid.