GLOBAL POSITIONIG SYSTEM(Gps)

8/13/2019 GLOBAL POSITIONIG SYSTEM(Gps)

1/62

ELECTRONICS & COMMUNICATION ENGINEERING

JIET School of Engineering & Technology for Girls JODHPUR

YEAR-2013

1


2/62

A PROJECT REPORTON

STUDY OF GPS

SUBMITTED BY

MANISHA CHOUDHARY

B.TECH 4

TH

YEAR(7

TH

SEM)

2


3/62

The Global Positioning System (GPS) is a space-basedsatellite navigation system that provides location and time

information in all weather conditions, anywhere on or near

the Earth where there is an unobstructed line of sight to

four or more GPS satellites.

It is also called NAVSTAR(Navigation Satellite Timing And

Ranging)

3


4/62

GPS was created and realized by the U.S. Department of

Defense (DoD) and was originally run with 24 satellites. It

became fully operational in 1994.

The system provides critical capabilities to military, civil andcommercial users around the world. It is maintained by the

United States government and is freely accessible to anyone

with a GPS receiver.

GPS satellites broadcast signals from space, and each GPSreceiver uses these signals to calculate its three-dimensional

location (latitude, longitude, and altitude) and the current

time.

4


5/62

The current GPS consists of three major segments.

SPACE SEGMENT (SS) :- The space segment is composed of

24 to 32 satellites in medium Earth orbit.

CONTROL SEGMENT (CS) :- The control segment is composed

of a master control station, an alternate master control

station, and a host of dedicated and shared ground antennas

and monitor stations.

USER SEGMENT (US) :- The user segment is composed of

hundreds of thousands of U.S. and allied military users of the

secure GPS Precise Positioning Service, and tens of millions

of civil, commercial, and scientific users of the Standard

Positioning Services.

Structure of GPS System

5
http://en.wikipedia.org/wiki/Medium_Earth_orbithttp://en.wikipedia.org/wiki/Medium_Earth_orbithttp://en.wikipedia.org/wiki/Medium_Earth_orbit


6/62

Space Segment

GPS satellites fly in circular orbits at an altitude of

20,200 km and with a period of 12 hours.

Powered by solar cells, the satellites continuously orient

themselves to point their solar panels toward the sun andtheir antenna toward the earth.

Orbital planes are centered on the Earth

Each planes has about 55 tilt relative to Earth's equator

in order to cover the polar regions.

6


7/62

Space Segment (Continued)

Each satellite makes two complete orbits each sidereal

day.

Sidereal - Time it takes for the Earth to turn 360

degrees in its rotation

It passes over the same location on Earth once each

day.

Orbits are designed so that at the very least, six

satellites are always within line of sight from anylocation on the planet.

7


8/62

Space Segment (Continued)

There are currently 32 actively broadcasting satellites

in the GPS constellation.

Redundancy is used by the additional satellites to

improve the precision of GPS receiver calculations.

A non-uniform arrangement improves the reliability and

availability of the system over that of a uniform

system, when multiple satellites fail

This is possible due to the number of satellites in theair today

8


9/62

Control Segment

The CS consists of 3 entities:

Master Control System

Monitor Stations

Ground Antennas

9


10/62

Master Control Station

The master control station, located at Falcon Air Force Base in

Colorado Springs, Colorado, is responsible for overall management

of the remote monitoring and transmission sites.

It calculates any position or clock errors for each individual

satellite from monitor stations and then order the appropriate

corrective information back to that satellite.

10


11/62

Monitor Stations

Six monitor stations are located at Falcon Air Force Base in

Colorado, Cape Canaveral, Florida, Hawaii, Ascension Island in the

Atlantic Ocean, Diego Garcia Atoll in the Indian Ocean, and

Kwajalein Island in the South Pacific Ocean.

Each of the monitor stations checks the exact altitude, position,

speed, and overall health of the orbiting satellites.

11


12/62

Monitor Stations (continued)

This "check-up" is performed twice a day, by each station, as the

satellites complete their journeys around the earth.

Variations such as those caused by the gravity of the moon, sun

and the pressure of solar radiation, are passed along to the master

control station.

12


13/62

Ground Antennas

Ground antennas monitor and track the satellites from horizon to

horizon.

They also transmit correction information to individual satellites.

13


14/62

User Segment

The user's GPS receiver is the US of the GPS system.

GPS receivers are generally composed of an antenna, tuned to the

frequencies transmitted by the satellites, receiver-processors, and

a highly-stable clock, commonly a crystal oscillator).

They can also include a display for showing location and speed

information to the user.

A receiver is often described by its number of channels this

signifies how many satellites it can monitor simultaneously. As of

recent, receivers usually have between twelve and twentychannels.

14


15/62

15


16/62

16


17/62

The GPS receiver uses the following information to determine a

position.

Precise location of satellites: When a GPS receiver is firstturned on, it downloads orbit information from all the satellitescalled an almanac. This process, the first time, can take as longas 12 minutes; but once this information is downloaded, it isstored in the receivers memory for future use.

Distance from each satellite: The GPS receiver calculates thedistance from each satellite to the receiver by using the distanceformula: distance = velocity x time. The receiver already knows

the velocity, which is the speed of a radio wave or 186,000 milesper second (the speed of light). To determine the time part of theformula, the receiver times how long it takes for a signal from thesatellite to arrive at the receiver. The GPS receiver multiplies thevelocity of the transmitted signal by the time it takes the signal toreach the receiver to determine distance.

17

How GPS work?


18/62

18


19/62

Triangulation to determine position: The receiverdetermines position by using triangulation. When it receives

signals from at least three satellites the receiver should be

able to calculate its approximate position (a 2D position).

The receiver needs at least four or more satellites tocalculate a more accurate 3D position. The position can be

reported in latitude/longitude, UTM, or other coordinate

system.

19


20/62

20


21/62

Trilateration

21


22/62

NASA produced short film that sumarizes GPS

http://www.youtube.com/watch?v=wi_3XwkA8cQ

Operational Overview Video

22
http://www.youtube.com/watch?v=wi_3XwkA8cQhttp://www.youtube.com/watch?v=wi_3XwkA8cQ


23/62

Navigational Systems

GPS satellites broadcast two different types of data in the primary

navigation signal.

Almanac sends time and status information about the

satellites.

Ephemeris has orbital information that allows the receiver to

calculate the position of the satellite.

23


24/62

Navigational Systems (contd)

Satellites broadcast two forms of clock information

Coarse / Acquisition code (C/A) - freely available to the public.

The C/A code is a 1,023 bit long pseudo-random code broadcast

at 1.023 MHz, repeating every millisecond.

Restricted Precise code (P-code) - reserved for military usage.

The P-code is a similar code broadcast at 10.23 MHz, but it

repeats only once a week. In normal operation, the anti-

spoofing mode, the P code is first encrypted into the Y-code, or

P(Y), which can only be decrypted by users a valid key.

24


25/62

GPS Frequencies

L1 (1575.42 MHz) - Mix of Navigation Message, coarse-acquisition

(C/A) code and encrypted precision P(Y) code.

L2 (1227.60 MHz) - P(Y) code, plus the new L2C code on the Block

IIR-M and newer satellites.

L3 (1381.05 MHz) - Used by the Defense Support Program to signal

detection of missile launches, nuclear detonations, and other

applications.

25


26/62

Clock errors

Signal errors (noise)

Interference in ionosphere and troposphere

Multipath errorSatellite position (ephemeris) error

Geometrical error (Geometric Dilution of

Precision - GDOP)

Intentional errors (Selective Availability - SA)

Human errors

Receiver errors (hardware, software, antenna)

Main GPS error sources

26


27/62

NMEA consists of sentences, the first word of

which, called a data type, defines the

interpretation of the rest of the sentence. Each

Data type would have its own uniqueinterpretation and is defined in the NMEA

standard. In the NMEA standard there are no

commands to indicate that the gps should do

something different. Instead each receiver justsends all of the data and expects much of it to be

ignored.

NMEA sentences

27


28/62

Recommended Minimum specific GPS/TRANSIT data (RMC) $GPRMC,1,2,3,4,5,6,7,8,9,10,11*hh


29/62

Assisted GPS(A-GPS) :

Assisted GPS, generally abbreviated as A-GPS or AGPS, is asystem that can under certain conditions improve the startup

performance, or time-to-first-fix(TTFF), of a GPSsatellite-

based positioning system. It is used extensively with GPS-

capable cellular phones

TYPES OF GPS

29
http://en.wikipedia.org/wiki/Time_to_first_fixhttp://en.wikipedia.org/wiki/Global_positioning_systemhttp://en.wikipedia.org/wiki/Cellular_phoneshttp://en.wikipedia.org/wiki/Cellular_phoneshttp://en.wikipedia.org/wiki/Cellular_phoneshttp://en.wikipedia.org/wiki/Global_positioning_systemhttp://en.wikipedia.org/wiki/Time_to_first_fixhttp://en.wikipedia.org/wiki/Time_to_first_fixhttp://en.wikipedia.org/wiki/Time_to_first_fixhttp://en.wikipedia.org/wiki/Time_to_first_fixhttp://en.wikipedia.org/wiki/Time_to_first_fixhttp://en.wikipedia.org/wiki/Time_to_first_fixhttp://en.wikipedia.org/wiki/Time_to_first_fix


30/62

Differential Global Positioning System (DGPS) is an

enhancement to Global Positioning Systemthat provides

improved location accuracy, from the 15-meter nominal GPS

accuracy to about 10 cm in case of the best

implementations.

DGPS uses a network of fixed, ground-based reference

stations to broadcast the difference between the positions

indicated by the satellitesystems and the known fixed

positions.

Differential GPS

30
http://en.wikipedia.org/wiki/Global_Positioning_Systemhttp://en.wikipedia.org/wiki/Satellitehttp://en.wikipedia.org/wiki/Satellitehttp://en.wikipedia.org/wiki/Global_Positioning_System


31/62

The GPS-Aided Geo Augmented Navigation (GAGAN) system,

aimed at making Indian skies safer, is undergoing final

operation phase which will be over in the next three years

before it is commissioned.

Once operational, GAGAN project would provide augmented

information for satellite navigation to aircraft flying over

Indian airspace and the routes over the high seas with high

level of accuracy, integrity and continuity

THE INDIAN PROJECT GAGAN

31


32/62

The Flight Management System (FMS), based on GAGAN, will

also help the operators to save time and money by managing

climb, descent and engine performance profiles of aircraft.

The FMS will also help in improving airport and airspace

access in all weather conditions, and the ability to meet theenvironmental and obstacle clearance constraints. GAGAN

also aims to enhance reliability and reduce delays by

defining more precise terminal area procedures that feature

parallel routes and environmentally optimised airspace

corridors.

GAGAN CONTD..

32


33/62

WAAS :The Wide Area Augmentation System(WAAS) isan air navigationaid developed by the Federal AviationAdministrationto augment the Global PositioningSystem(GPS), with the goal of improving its accuracy,integrity, and availability.

WAAS uses a network of ground-based reference stations,in North Americaand Hawaii, to measure small variations inthe GPS satellites' signals in the western hemisphere.Measurements from the reference stations are routed tomaster stations, which queue the received Deviation

Correction (DC) and send the correction messages togeostationary WAAS satellites in a timely manner (every 5seconds or better). Those satellites broadcast the correctionmessages back to Earth, where WAAS-enabled GPS receiversuse the corrections while computing their positions toimprove accuracy.

Wide Area Augmentation System

33
http://en.wikipedia.org/wiki/Air_navigationhttp://en.wikipedia.org/wiki/Federal_Aviation_Administrationhttp://en.wikipedia.org/wiki/Federal_Aviation_Administrationhttp://en.wikipedia.org/wiki/Global_Positioning_Systemhttp://en.wikipedia.org/wiki/Global_Positioning_Systemhttp://en.wikipedia.org/wiki/North_Americahttp://en.wikipedia.org/wiki/Hawaiihttp://en.wikipedia.org/wiki/Western_hemispherehttp://en.wikipedia.org/wiki/Western_hemispherehttp://en.wikipedia.org/wiki/Hawaiihttp://en.wikipedia.org/wiki/North_Americahttp://en.wikipedia.org/wiki/Global_Positioning_Systemhttp://en.wikipedia.org/wiki/Global_Positioning_Systemhttp://en.wikipedia.org/wiki/Federal_Aviation_Administrationhttp://en.wikipedia.org/wiki/Federal_Aviation_Administrationhttp://en.wikipedia.org/wiki/Air_navigation


34/62

34


35/62

Dilution of Precision (DOP) reflects each satellites position

relative to the other satellites being accessed by a receiver.

There are four distinct kinds of DOP.

Position Dilution of Precision (PDOP) is the DOP value usedmost commonly in GPS to determine the quality of a

receivers position.

Its usually up to the GPS receiver to pick satellites which

provide the best position triangulation.

Some GPS receivers allow DOP to be manipulated by theuser.

DILUTION OF PRECISION(DOP)

35


36/62

DOP has several components:

PDOP -Position Dilution of Precision (3D),sometimes knownas spherical DOP (1.63)

HDOP - Horizontal Dilution of Precision (Latitude, Longitude)

(1.15)

VDOP - Vertical Dilution of Precision (Height) (1.15)

TDOP - Time Dilution of Precision (Time)(0.58)

Poor GDOP occurs when the satellite angles to the field

receiver are similar (signals are all coming in to the receiver in

the same angles)

Good GDOP is achieved when the 4 satellites used when the

angles are different

36


37/62


38/62

38


39/62

FALCON GPS TRAINER

39


40/62

SKY PLOT

40


41/62

NMEA SENTENCES

41


42/62

INTERFACING WITH OPEN SOURCE SOFTWARE

(MINI GPS)

42


43/62


44/62

Cold Start : the cold start is when the GPS device dumps allthe information, attempts to locate satellites and then

calculates a GPS lock. This takes the longest because there isno known information.

Channel : It tells the number of satellites the GPS cancommunicate with at one time. At a given time there are at

least 24, more often about 30 satellites that make up the GPSsystem.

Selective Availability: Selective Availability is a term used todescribe the way signals from the GPS satellites in orbit around

the Earth are masked.It is aimed to degrade the performance ofthe GPS. The U.S. Government controls the satellites, and uses

Selective Availability to confuse the GPS receiver so it can't find

your exact position.

44


45/62

Pseudo Random Noise Number: A clock reading at thetransmitted antenna is compared with the clock reading at the

receiver antenna. But since the two clocks are not strictly

synchronized, the observed signal travel time is biased with

systematic synchronization error. The satellites are identified

by the receiver by means of PRN-numbers. Real GPS satellites

numbered from 1-32

45


46/62

46

Fl h t f


47/62

Flow chart for

decoding NMEA

sentence

47

START

Get NMEA sentences from serial port and wait

If sentence

containGPRMC

Separate the fields and display

If Enter0x0D is

encountere

Y

Y N

If $

found

Y


48/62

PIC is a family of modified Harvard architecture

microcontrollers made by Microchip Technology

Microcontroller Unit (MCU)

Microprocessor unit (MPU)

Program memory for instructions Data memory for data

I/O ports

Support devices such as timers

48

Microchip PIC


49/62

49

Microcontroller Unit


50/62

50

PIC18F MPU and Memory


51/62

Microprocessor Unit

Includes Arithmetic Logic Unit (ALU), Registers, and Control

Unit

Arithmetic Logic Unit (ALU)

Instruction decoder

16-bit instructions

Status register that stores flags

5-bits

WREG working register

8-bit accumulator

330_02 51


52/62

Microprocessor Unit

Registers

Program Counter (PC)

21-bit register that holds the Program Memoryaddress

Bank Select Register (BSR) 4-bit register used in direct addressing the Data

Memory

File Select Registers (FSRs)

12-bit registers used as memory pointers in

indirect addressing Data Memory Control unit

Provides timing and control signals

Read and Write operations

330_02 52


53/62

PIC18F - Address Buses

Address bus

21-bit address bus for Program Memory

Addressing capacity: 2 MB

12-bit address bus for Data Memory Addressing capacity: 4 KB

330_02 53


54/62

Data Bus and Control Signals

Data bus

16-bit instruction/data bus for Program Memory

8-bit data bus for Data Memory

Control signals Read and Write

330_02 54


55/62

Data Memory with Access Bank

330_02 55


56/62

Instruction Descriptions Copy (Move) 8-bit number (Literal) into W register

Mnemonics: MOVLW 8-bit

Binary format:

0000 1110 XXXX XXXX (any 8-bit number)

Copy (Move) contents of W register into PORTC(File)

Mnemonics: MOVWF PORTC, a (a indicates that PORTC is in the Access Bank)

Binary format:0110 1110 1000 0010 (82His PORTC address)

330_02 56


57/62

Illustration

Program (software)

Logic 0 to TRISC sets up PORTC as an outputport

Byte 55Hturns on alternate LEDs

MOVLW 00 ;Load W register with 0

MOVWF TRISC ;Set up PORTC asoutput

MOVLW 0x55 ;Byte 55Hto turn onLEDS

MOVWF PORTC ;Turn on LEDs

SLEEP ;Power down

330_02 57


58/62

58

PICkit-3

The Status LEDs indicate the status of the PICkit 3.


59/62

1. Power (green) Power is supplied to the PICkit 3 via the USB port.

2. Active (yellow) The PICkit 3 has connection to the PC USB port and

the Communication link is active.

3. Status:Busy (red) The PICkit 3 is busy with a function in progress,

such as Programming.

PicKit3 Programmer/Debugger

Microchips PICkit 3 In-Circuit Debugger/Programmer uses in-circuit

debugging logic incorporated into each chip with Flash memory to

provide a low-cost hardware debugger and programmer

The MPLAB PICkit 3 is connected to the design engineer's PC using a full

speed USB interface and can be connected to the target

59


60/62

The MPLAB X IDE is the new graphical, integrated debugging

tool set for all of Microchips more than 800 8-bit, 16-bit

and 32-bit MCUs and digital signal controllers, and memory

devices. It includes a feature-rich editor, source-level

debugger, project manager, software simulator, andsupports Microchips popular hardware tools, such as the

MPLAB ICD 3 in-circuit debugger, PICkit 3, and MPLAB PM3

programmer.

Sample view of mplab

60

MPLAB Integrated DevelopmentEnvironment


61/62

61


62/62

GLOBAL POSITIONIG SYSTEM(Gps)

Documents

Transcript of GLOBAL POSITIONIG SYSTEM(Gps)