DIFFERENTIAL GLOBAL POSITIONING SYSTEM

SHREE MADHAV INSTITUTE OF COMPUTER SHREE MADHAV INSTITUTE OF COMPUTER & INFORMATION TECHNOLOGY& INFORMATION TECHNOLOGY

PRESENTED BY : Maury Anand L. (1570)

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AgendaAgenda

Abstract Introduction History of DGPS How DGPS system works Error Possibilities in GPS Advantages Limitations Applications References

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Normal GPS (Global Positioning System) is not accurate enough for the applications.

For greater accuracy, a Differential GPS system will be implemented. To do this, two GPS units are required. A base station, with a known position, sends error correction data to a mobile unit.

The error correction data is sent wirelessly through a radio link.

The data can then be viewed on a laptop computer for statistical analysis.

Abstract

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What is DGPSDGPS is a satellite-based for Navigation.DGPS improves the GPS position and speed measurements.DGPS provides perfect location within 10 cm.

Introduction

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The military requires very precise measurements across their

Battle scene.

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Global positioning system is developed and funded by US Government and managed by department of defense.

1973 - Decision to develop a satellite navigation system for military.

1974 -1979 conducted system tests by US air force and navy. 2000 – Final deactivation of SA to give positional accuracy of

20M from 100M. 2005 –Launching of the IIRM GPS satellite that supports the

new military M signal and the second civil signal L2C.

History of GPS

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History of DGPS

This technique was accuracy and integrity. This technique was developed in the early 1980s, and it is developed in the early 1980s, and it is widely used in various forms.

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DGPS is a method of improving the accuracy of your receiver by adding a local reference station to augment the information available from the satellites. It also improves the integrity of the whole GPS system by identifying certain errors.

Differential GPS uses one unit at a known location and a rover.

The stationary unit compares its calculated GPS location with the actual location and computes the error.

The rover data is adjusted for the error.

DGPS in Detail

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1) Real-Time DGPS

2) Satellite Differential Services

Types of DGPS System

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Real time DGPS

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Satellite Differential Services

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The receiver is not synchronized with the atomic clock in the satellite.

The estimate of the position of the satellite. ”Multi path errors” : Ghost signals from ”Multi path errors” :

Ghost signals from reflected radio waves. Not free sight to many enough satellites. Noise in the receiver.

Error Possibilities in GPS

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Error Value

Ionosphere 4.0 meters

Clock 2.1 meters

Ephemeris 2.1 meters

Troposphere 0.7 meters

Receiver 0.5 meters

Multipath 1.0 meter

Total 10.4 meters

Source Of Errors in GPS

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Noise ErrorBaises ErrorBlunder ErrorClock Error

GPS Errors

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Two Novatel® RT-20 ReceiversOperate at 1575.42 MHz12 Channel ReceiversTwo Free Wave® RadiosOperate at 928 MHz20 mile line of sight rangeLaptop, Computer

Equipment Used

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Master receiver and roversMaster receiver is kept at known point. Relative position of rovers are fixed with respect to

the fixed with respect to the master receiver.

Components of DGPS

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How DGPS System Works

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GPS DGPS

Errors Removed by DGPS

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Errors Removed by DGPS

Signal Noise 0-30 meters All Removed Clock Drift 0-1.5 meters All Removed Multipath 0-1 meters All Removed Ephemeris Data 1-5 meters All Removed Troposphere 0-30 meters All Removed Ionosphere 0-30 meters Mostly Removed

DGPS helps to know perfect location on the earth. Provide accurate data within a minute. GPS is quite accurate; however, using DGPS pushes its

accuracy even further. GPS/DGPS makes A/L guidance every precise as oppose to

ILS and MLS.

Advantages

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The coverage area to take advantage of DGPS is limited. To ensure greater coverage area more DGPS stations need to

be added.  The position accuracy degrades as the separation between

DGPS and aircraft GPS-Rx increases.

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Limitations

Air NavigationBy using it a pilot can receive constant information about

where the plane is in 3 dimensions. Weather forecasting

Where atmospheric information can be gained from its effects on the satellite signals.

Train Control For such things as avoiding collisions and routing.

Marine, Ship Navigation By using it a ship can receive constant information about current

location and parking location on port.

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Applications

Website :www.en.wikipedia.orgwww.dgll.nic.in

Location :Hazira DGPS Station

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References