SEMINAR REPORT ON “GLOBAL POSITIONING

SYSTEM”

Presented By: IQxplorer

GLOBAL POSITIONING SYSTEM

CONTENTS INTRODUCTION WHAT IS GPS ? FACTS ABOUT GPS. HOW GPS WORKS? WHAT’S THE SIGNAL? ERRORS CORRECTING ERRORS CONCLUSION

1. INTRODUCTION Trying to figure out where you are and

where you're going is probably one of man's oldest pastimes. Navigation and positioning are crucial to so many activities and yet the process has always been quite complicated .

So the result is the Global Positioning System, a system that's changed navigation forever.

2. WHAT IS GPS ?

The Global Positioning System (GPS) is a worldwide radio-navigation system formed from a constellation of 24 satellites and their groundstations.There are 5 ground stations: Hawaii, Ascension Island, Diego Garcia, Kwajalein, and Colorado Springs.

3. FACTS ABOUT GPS ! The first GPS satellite was launched in

1978. A full constellation of 24 satellites was

achieved in 1994. Each satellite is built to last about 10

years. Replacements are constantly being built and launched into orbit.

A GPS satellite weighs approximately 2,000 pounds and is about 17 feet across with the solar panels extended.

Transmitter power is only 50 watts or less.

4. HOW GPS WORKS?Here's how GPS works in five logical steps: The basis of GPS is “triangulation” from satellites. To "triangulate," a GPS receiver measures

distance using the travel time of radio signals. To measure travel time, GPS needs very accurate

timing which it achieves with some tricks. Along with distance, you need to know exactly

where the satellites are in space. High orbits and careful monitoring are the secret.

Finally you must correct for any delays the signal experiences as it travels through the atmosphere .

5.What's the signal? GPS receivers take this information and use

triangulation to calculate the user's exact location. Essentially, the GPS receiver compares the time a signal was transmitted by a satellite with the time it was received.

In the case of GPS we're measuring a radio signal so the velocity is going to be the speed of light or roughly 186,000 miles per second.

The timing problem is tricky. First, the times are going to be awfully short. If a satellite were right overhead the travel time would be something like 0.06 seconds. So we're going to need some really precise clocks, called atomic clocks, equipped in the satellites.

Now the Distance = Velocity X Time So Distance= 1,86,000 X 0.06 =11,160 miles.

A GPS signal contains three different bits of information —

1.A pseudorandom code2.Ephemeris data 3.Almanac data.

ERRORS Sometimes errors are occurred while the

data are transmitted from the satellites to the GPS receivers.

Ionosphere and troposphere delays — Signal multipath — Receiver clock errors — Orbital errors — Number of satellites visible — Satellite geometry/shading — Intentional degradation of the satellite

signal —

CORRECTING ERRORS 1. Some errors can be factored out

using mathematics and modeling. 2. The configuration of the satellites

in the sky can magnify other errors. 3. Differential GPS can eliminate

almost all error.

Summary of GPS Error Sources

1. Satellite Clocks 1.5 02. Orbit Errors 2.5 03. Ionosphere 5.0 0.44. Troposphere 0.5 0.25. Receiver Noise 0.3 0.36 .Multipath 0.6 0.6

CONCLUSION

Mapping and surveying companies use GPS extensively. In the field of wildlife management also. GArchaeologists and explorers are using the system. Anyone equipped with a GPS receiver can use it as a reference point to find another location. With a basic knowledge of math and science, plus a hand-held GPS receiver, you could be an instant hero if you and friends got lost on a camping trip.PS-equipped balloons are monitoring holes in the ozone layer over the polar regions, and air quality is being monitored using GPS receivers.