GPS PPT

MINOR PROJECT

GLOBAL POSITIONING SYSTEM

[GPS]

Simulation of a GPS Handheld Receiver

Under the noble guidance ofMr. ChanderPal Sharma

Submitted By:

Ishika Goel[1671482808]

Sushant Sethi[1791482808]

OBJECTIVE OF THE PROJECT

A Project in which we build a simulation that gives the location, in 3D, ‘the latitude, longitude and altitude’, of handheld GPS receivers, based on the inputs received by the same from the satellites. ‘The Adaptive Missile Guidance using GPS’ is cited as an example and its function is framed.

INTRODUCTION TO GPS The Global Positioning System (GPS) is a space based

radio positioning/navigation system that will provide three-dimensional position, velocity and time information to suitably equipped users anywhere on or near the surface of the earth.

  The Global Positioning System (GPS) is a system of 31

satellites which circle the earth twice a day in a very precise orbit and transmit information to earth. The GPS navigator we used during our project, must continuously see at least four of these satellites to calculate our position.

How GPS Works Satellites send radio signals to the receivers which are on

earth surface. Using these signals receiver calculates its location on earth.

Using the concept of Spherical Intersections between the outputs of the satellites and the Earth’s surface, a region of probable location of the receiver is calculated.

Control Segment

Space Segment

User Segment

Three Segments of the GPSThree Segments of the GPS

Monitor Stations

GroundAntennas

Master Station

Four Basic Functions of GPS

Position and coordinates.

The distance and direction between any two waypoints, or a position and a waypoint.

Travel progress reports.

Accurate time measurement.

Our Goal

We will build a MATLAB code, which would take in the position of the satellites as inputs from the user.

There are a few assumptions made. Using a mathematical computation, we would try to

calculate the position of the GPS receiver.

Definition of the Problem

All the points with di distances from each satellite i, defines a sphere in the space. We also assume that earth is spherical. The intersection of these two spheres (the earth and sphere defined by all the points with di distances from each satellite i) is a circle on earth surface.For each satellite i, it is the same situation. If we can take the exact distances, these circles - formed with a satellite and earth- intersect exactly at one point and it is our point P.

s3

s2

s1

P

d

Formation of a common region

Ambiguity lies in this region

Position Fix

A position is based on real-time satellite tracking. It’s defined by a set of coordinates. It has no name. A position represents only an approximation of the

receiver’s true location. A position is not static. It changes constantly as the GPS

receiver moves (or wanders due to random errors). A receiver must be in 2D or 3D mode (at least 3 or 4

satellites acquired) in order to provide a position fix. 3D mode dramatically improves position accuracy.

Waypoint A waypoint is based on coordinates entered into a GPS

receiver’s memory. It can be either a saved position fix, or user entered

coordinates. It can be created for any remote point on earth. It must have a receiver designated code or number, or a user

supplied name. Once entered and saved, a waypoint remains unchanged in

the receiver’s memory until edited or deleted.

Three Satellites (2D Positioning)Three Satellites (2D Positioning)

Three Dimensional (3D) PositioningThree Dimensional (3D) Positioning

Mathematical Computation Using the inputs given, we would formulate the equation

of a sphere defined by those coordinates, this would be done for each of the satellites.

The intersection of these spheres would give rise to a common region.

Once the common region is calculated, we would implement a probability distribution in that region to compute the location of the receiver.

GPS Satellite Geometry Satellite geometry can affect the quality of GPS signals and accuracy

of receiver trilateration. Dilution of Precision (DOP) reflects each satellite’s position relative

to the other satellites being accessed by a receiver. It’s usually up to the GPS receiver to pick satellites which provide the

best position triangulation. Some GPS receivers allow DOP to be manipulated by the user.

Good Satellite GeometryGood Satellite GeometryN

S

W E

Good Satellite GeometryGood Satellite Geometry

Poor Satellite GeometryPoor Satellite GeometryN

S

W E

Poor Satellite GeometryPoor Satellite Geometry

Practical ErrorsPractical Errors

Earth’s Atmosphere

Solid Structures

Metal Electro-magnetic Fields

THANK YOU