GPS Seminar In Computer Science Engineering

Definition Of Gps
 GPS Is A Satellite Navigation System

          The GPS is a worldwide radio navigation system formed from a constellation of 24 satellites and their ground stations. GPS uses these “manmade stars” as reference points to calculate the 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 is like giving every square meter on the planet a unique address, the system was designed for and is operated by the U. S. military. GPS is funded by and controlled by the U. S. Department of Defense (DOD). While there are many thousands of civil users of GPS world wide. GPS has mainly 3 parts the space segment, the user segment and the control segment. They are collectively called as GPS Elements.

GPS Seminar In Computer Science Engineering

GPS Elements

          GPS has mainly three elements they are the space segment  the user segment  and  the control segment .The space segment consists of the nominal GPS satellite network that consists of a constellation of 24 satellites that orbit the earth in 12 hrs. These space vehicles (SVs) send radio signals from space. The Control Segment consists of a system of tracking stations located around the world that make sure the satellites are working properly. The GPS User Segment consists of the GPS receivers and the user community. GPS receivers convert SV signals into position, velocity, and time estimates. Four satellites are required to compute the four dimensions of X, Y, Z (position) and Time. GPS receivers are used for navigation, positioning, time dissemination, and other research. Now we can discuss about these GPS elements in detail.

Measuring Distance

          Here we can discuss how the receiver and satellite work together to make this measurement .GPS receiver calculates the distance to GPS satellites by timing a signal’s journey from satellite to receiver, as it turns this is a fairly elaborate process.

          At a particular time, the satellite begins transmitting a long, digital pattern called a pseudo-random code. The receiver begins running the same digital pattern also exactly at that time. When the satellite’s signal reaches the receiver, its transmission lag a bit behind the receiver’s playing of the pattern. The length of the delay is the signal’s travel time. The receiver multiplies this time with the speed of the signal to determine how far the signal traveled.

          In order to make this measurement the receiver and satellite both need clocks that can be synchronized down to the nanoseconds. Thus every satellite is equipped with an expensive atomic clocks and the receiver itself uses an ordinary quartz clock, which it constantly resets.

          In order for the distance information to be of any use, the receiver also has to know where the satellites actually are. The GPS receiver simply stores an almanac data that tells it where every satellite should be at any given time. Things like pull of the moon and the sun do change their orbits very slightly  the Department Of Defense constantly monitors their positions exactly and transmits any adjustments to all GPS receivers as part of the satellite’s signals.