Transcript pptx
Global Positioning System
(GPS)
Allen Zhao, Guanlun He, Matt Cui
Agenda
• History
• How the Technology Works
• Other uses
• GPS Versions
• Available devices
• Indoor Positioning System
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History
• Created by American Department of
Defense in the 1960s during the Cold
War
• Opened to the public in 1990
• GPS released to public after a Korean
commercial plane shot down due to
accidentally venturing into Russian
airspace
http://www.big-lies.org/NUKELIES/www.insidegnss.com/auto/popupimage/GPS%20IIFassembly-Flag.jpg
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How it works
• 24 operational GPS satellites revolve around
the earth
• Each travel along one of 6 orbits
•
Orbits are created strategically
• Each point on earth needs at least 4 satellites
pointing at you
•
Your receiver only needs 3 - trilateration
•
One is used as an auxiliary
https://upload.wikimedia.org/wikipedia/commons/9/9c/Co
nstellationGPS.gif
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Trilateration
Satellite A says “You are 50,000 km away from me”
http://moorefarmsbg.org/wpcontent/uploads/2014/05/GPS_3Dtrilateration.png
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Trilateration
https://www.eeducation.psu.edu/natureofgeoinfo/sites/www.eeducation.psu.edu.natureofgeoinfo/files/image/gps_r
anging_3.jpg
Satellite A says “You are 50,000 km away from me”
Satellite B says “You are 62,300 km away from me”
Satellite C says “You are 40,800 km away from me”
http://farm3.static.flickr.com/2656/3728939543_15aaefe
316_o.jpg
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Trilateration
https://www.eeducation.psu.edu/natureofgeoinfo/sites/www.eeducation.psu.edu.natureofgeoinfo/files/image/gps_r
anging_3.jpg
Satellite A says “You are 50,000 km away from me”
Satellite B says “You are 62,300 km away from me”
Satellite C says “You are 40,800 km away from me”
Satellite D can be used to get altitude coordinate
Though, normally GPS devices will use the surface of the earth
(You probably won’t be using Google Maps if you’re
you’re floating in space)
http://farm3.static.flickr.com/2656/3728939543_15aaefe
316_o.jpg
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Trilateration
• GPS system receives signal from satellites and times
how long it took for the signal to arrive
•
this gives distance
•
Need a very precise timing mechanism
•
Take into account special and general relativistic factors
• All GPS satellites all have a very precise atomic clock
• Receiver also needs to know precise time
•
Has a quartz oscillator that constantly syncs with the satellites
time
http://moorefarmsbg.org/wpcontent/uploads/2014/05/GPS_3Dtrilateration.png
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Other Uses
Because of their very precise timing , GPS timers are used by time-sensitive
systems
•
Stock market
•
Hollywood studios (time audio and video data & multi-camera sequencing)
•
GPS timers
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GPS Satellites Types
Type IIA (discontinued)
One of the earliest GPS systems available to the public
Recently discontinued this year
Two distinct encoding types: Precise code and Coarse/Acquisition code
Type IIF (current)
Was designed to replace the IIA satellite
First ones to have precise atomic clocks
20 feet accuracy
New military (M) code that has enhanced security
Type III (2017)
Accurate to an arms length
Stronger signal, longer life span
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GPS Modules - EECS 373 Application
•
Around $20 - $50
•
Wide range of capabilities depending on the
module.
•
Many have flash memory for data logging
applications.
•
Couple require high range antenna to get a
better signal.
•
Relays information including but not
limited to position, velocity, and time.
https://www.sparkfun.com/products/11058
https://www.sparkfun.com/products/1374
0
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How to use them
•
Most communicate in some form of serial communication.
•
Majority uses rs232/ uart, a couple use SPI and I2C
•
Very easy to use with high level microcontrollers like Arduinos and
Raspberry Pis
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Sample GPS packet
$GPRMC,194530.000,A,3051.8007,N,10035.9
989,W,1.49,111.67,310714,,,A*74
$GPRMC
Time
Latitude, [N/S]
Longitude, [E/W]
Speed in knots
Track Angle
Date
Magnetic variation
Checksum
http://www.doctormonk.com/2012/05/sparkfunvenus-gps-and-arduino.html
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#include <SoftwareSerial.h>
SoftwareSerial gpsSerial(10, 11); // RX, TX (TX not used)
const int sentenceSize = 80;
char sentence[sentenceSize];
void setup(){
Serial.begin(9600);
gpsSerial.begin(9600);
}
void loop(){
static int i = 0;
if (gpsSerial.available()){
char ch = gpsSerial.read();
if (ch != '\n' && i < sentenceSize){
sentence[i] = ch; i++;
}
else{
sentence[i] = '\0';
i = 0;
displayGPS();
}
}
}
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IPS - Indoor Positioning System
• GPS does not work well inside buildings because the signal struggles to move
through solid objects.
• Interference can corrupt the signal
• There is no standard for IPS but there are many commercial systems
• IPS does not use satellites, but instead can be implemented several ways
including magnetic positioning, light, and measuring the distance to nearby
nodes
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Magnetic Positioning
Magnetic Positioning uses a compass like technology to analyze the magnetic field
produced by the earth and how it interacts with the steel and other materials in a
building
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Commercial IPS products
• http://www.wifarer.com/ (mobile app) uses Wifi Nodes
• http://www.locata.com/ Uses a module to create a beacon, simillar to GPS
• https://www.indooratlas.com/ Uses Magnetic Fields
• ByteLyte Uses LED Lighting
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Questions?
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Works Cited
https://en.wikipedia.org/wiki/Global_Positioning_System
https://en.wikipedia.org/wiki/GPS_signals
https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System
http://www.gps.gov/systems/gps/space/
http://www.nasa.gov/directorates/heo/scan/communications/policy/GPS_History.html
http://www.trimble.com/gps_tutorial/howgps.aspx
http://electronics.howstuffworks.com/10-unconventional-uses-gps.htm
https://www.sparkfun.com/categories/17
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