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Basics of Global Navigation Satellite Systems
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Satellite Navigation
Univ.-Prof. Dr.-Ing. habil. Michael MeurerChair of Navigation
RWTH Aachen University&
German Aerospace Center (DLR)
Email: [email protected]
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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When, Where and for Whom?
For whom:Department of Electrical Engineering and Information Technology Information and Communication Technology (IKT) (Module B) Micro and Nano Electronics (MiNa) (Module C) System Engineering and Control (AT) (Module C) … everybody else who is interested in the topic …Module “Wahl“ Master of Science 1st or 2nd year, Bachelor of Science 3rd year …
Course:
Lecture (2 SWS) and Exercise (1 SWS), ECTS credits: 4organized as bi-weekly course in two-weeks interval, details about the time planningis available in the CAMPUS system.
More Details:
see webpage in CAMPUS System, slides will be made available via L2P
First lecture:
21.10.15 , will take place at 10:00 in bld. 1090 (Rogowski) room 301 (E1)
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Dates and Times
Date 10:00-11:30 11:35-13:00 14:15-15:45
21.10.2015 L L -
04.11.2015 L L -
18.11.2015 L L 2E
02.12.2015 L L 2E
16.12.2015 L L 2E
13.01.2016 L L 2E
03.02.2016 L L 2E
10.02.2016 L L (2E)
L = lecture (90min)E = exercise (45min)
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Practical arrangements
lecture slides will be distributed via L2P in advance of the lecture
exercises will be distributed during the lecture
exercises will also be made available via internet
written examination (90min) at the end of the lecture period/beginning of the examinationperiod
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Examination
Written examination (90min) on
Thursday, 25.02.2016, 11:00-12:30 (please arrive early enough, entrance from 10:30 on)
In bld. 1132 (Hörsaalgebäude HKW "Toaster“ / Campus Mitte) room 101 (HKW 1)
The use of the following material is permitted: writing material and a non-programmable pocket calculator. All other items, including in particular books, cell phones,... are prohibited.
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Motivation
Space and Navigation systemshave the same relation ship as
Time and Clock
Human beings exist in time and space!
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Some Highlights of the Course
Introduction to radio based determination of position, time and velocity
Position and velocity estimation Satellite constellations and orbits Signals and navigation services (GPS and Galileo) Acquisition and tracking Discriminators for delay, frequency and phase and associated loops Multipath, ionospheric and tropospheric propagation and their
mitigation Accuracy of position and time Reference systems for position and time Relativistic corrections
GPS
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Goals of the Course
Overview of and introduction to satellite navigation Modelling of navigation problems Understanding challenges Solution of navigation problems by appropriate technologies
Systematic study and discussion of the topic from the basics Performance analysis of systems Ultimate limits of performance
Introduction in latest and planned satellite navigation systems
Motivation for further projects/activities in the field, e.g. bachelor thesis, master thesis, seminars, satellite navigation lab … contribution to research at our labs at RWTH Aachen andGerman Aerospace Center (DLR) / Oberpfaffenhofen
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Who is DLR ?
Deutsches Zentrum für Luft- und Raumfahrt /German Aerospace Space Center (DLR)
German „NASA“ –National Space Agency andNational Aeronautics and Space Research Center of Germany (Großforschungs-einrichtung des Bundes)
Research Topics: Space, Aeronautics, Transportation, Energy and Securityincl. Communications and Navigation
approx. 7500 employees, 32 institutes
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Who is DLR ?
Deutsches Zentrum für Luft- und Raumfahrt /German Aerospace Space Center (DLR)
Institute of Communications and Navigation
DLR Center of Excellence forSatellite NavigationProf. Dr. Michael Meurer
approx. 80 scientists workingin navigation research topics
Sites: Oberpfaffenhofen (Munich)Neustrelitz
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Who is DLR ?
Deutsches Zentrum für Luft- und Raumfahrt /German Aerospace Space Center (DLR)
Galileo Control Center @ Oberpfaffenhofencontrolling / operation Galileo Constellation
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Embedding of Course
Seminar
Satellite Navigation
Project Work(Master Thesis,
Bachelor Thesis)Satellite Navigation
LabScientific Project
Work(PhD)
Navigation for Safety-Critical Applications
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Expected Precognition
In the lecture the following previous knowledge is assumed:
Coordinate Systems: Cartesian, polar and spheric coordinate systems
Linear Algebra: Matrix calculations, eigenvalues, least squares
Probability calculus: Random variable, probability, probability density, mean, variance,
correlation, …
Signal theory: Frequency, Fourier transformation, spectrum, bandwidth
Linear system theory: Equivalent low-pass systems, impulse response, space state
description
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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References
References and selected textbooks:
E.D.Kaplan, C.J. Hegarty, Ed., Understanding GPS, Principles and Applications, Artech House, Boston, London, 2nd, Ed. 2006
P. Misra, P. Enge, Global Positioning System, Signal, Measurements, and Performance, Ganga-Jamuna Press, Lincoln, MA, 2001
B.W. Parkinson and J.J. Spilker Jr., Global Positioning System: Theory and Applications, Vol. I and II, Am. Inst. of Aeronautics and Astronautics, Inc., Washington DC, 1996
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Outline and Structure (1)
1. Introduction
1.1 Historical Overview of Navigation
1.2 Challenges and Applications
1.3 Definitions
1.4 Understanding the Satellite Navigation Principal
2. From Early Days of Satellite Navigation to Today
2.1 Sputnik
2.2 TRANSIT
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Outline and Structure (2)
3. NavStar GPS – Status and Architecture
3.1 System Aspects
3.2 Space Segment
3.3 Ground Control Segment
4. Galileo – Status and Architecture
4.1 System Aspects
4.2 Space Segment
4.3 Ground Control Segment
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Outline and Structure (3)
5. Position, Time and Velocity in GNSS
5.1 Position and Time Determination
5.2 Velocity Determination
5.3 Dilution of Precision
5.4 Error Contributions
6. Satellite Orbits
6.1 Orbit Dynamics
6.2 Description and Modelling of Orbits
6.3 Determination of Satellite Positioning
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Outline and Structure (4)
7. Signals and Services
7.1 Spread Spectrum Principle
7.2 Modulation and Pulse Forms
7.3 Frequency Spectrum and Services
7.4 Reference Frequency Generation
8. Pseudorange Estimation
8.1 Correlation Principle
8.2 Signal Aquisition
8.3 Signal Tracking
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Outline and Structure (5)
9. Radio Propagation and Error Contributions
9.1 Basic effects of wave propagation
9.2 Ionospheric effects and space weather impact
9.3 Tropospheric effects
9.4 Multipath propagation
9.5 Interference
Satellite NavigationChapter 1:
Introduction – From early to modern times
Univ.-Prof. Dr.-Ing. habil. Michael MeurerChair of Navigation
RWTH Aachen University&
German Aerospace Center (DLR)
Email: [email protected]
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
21
Outline and Structure
1. Introduction
1.1 Historical Overview of Navigation
1.2 Challenges and Applications
1.3 Definitions
1.4. Understanding the Satellite Navigation Principal
2. From Early Days of Satellite Navigation to Today
2.1 Sputnik
2.2 TRANSIT
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Historic Overview - Origin of Navigation
Usage of Natural Phenomena:
Navigation using observations of Sun, Stars, Moon, Polar Star, Southern Cross
Birds, Wind, Sea Current
4000 B.C.: First astro-navigation in India, Egypt and Libanon
2000 B.C.: First Sea and River maps in China
1000 B.C.: Phoenician travel over open sea
Distance and Direction measurement in china: Distance measurement (odometer) using
drum waggon 1 drumbeat per Li (approx. 0.5 km)
3. Century: „coach with arm constantly showingto the south“
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Historic Overview - Greeks and Romans
First comprehension of astronomy:
2. Century B.C. : Hipparchus proposes systems of longitude andlattitude
100-160 A.D: Ptolemy composes „Almagest“ (astronomic system of the Greeks)
mathematical description of celestial bodies
Spheric trigonometry
Sine tables
standard book for mathematical astronomyup to the 17. century
Claudius Ptolemy(85-165)
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Historic Overview - Middle Ages
Begin of systematic utilization of technical measurement utilities:
approx. 1200: magnetic compass (in China and Italy)
13. century : Introduction of „Quadrant“ in Europefor sea shipping (instrument formeasuring „height“ of celestial bodies)
16. century : Mercator projection (=isogonic projection)
1609/1619 : Kepler (1571-1630) formulates his3 basic laws about planet motion
Johannes Kepler(1571-1630)
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Historic Overview –Solving the Longitude Problem
Easy determination of Lattitude on northern hemisphere by measurement of angle betweenpolar star and horizont
Determination of Longitude using globallyavailable clock, time difference (e.g. sun rise) allows calculation of longitude difference(24h is equal to 360°)
Availability of sufficiently stable clock not before 18th century
North Pole
Polar star
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Historic Overview –Longitude Challenge
1600: Spanish King offers a prize for accurate Longitude Determination
1714: Longitude Act of the British parliament:£10,000 for a method that could determine longitude
within 60 nautical miles (111 km) £15,000 for a method that could determine longitude
within 40 nautical miles (74 km) £20,000 for a method that could determine longitude
within 30 nautical miles (56 km). determination of longitude with an accuracy of 0.5°onship trip to Westindia” (Caribbean Islands) – Award is about 200-times the annual salary of an astronomer
Source: National Maritime Museum, London
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Historic Overview –Solving the Longitude Problem
Accuracy before:1 Min / Day(28km/day at theequator)
Accuracy after:0,5 Sec / Day(0,23km/day at theequator)
John Harrison‘s Chronometers H-4 completed in 1759, tested in
61/62 and 64
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Historic Overview – 19th Century
1842 : Discovery of the Doppler Effect
- sonic depth finder
1884 : Washington Conference
- definition of „prime median“ at Greenwich- definition of Greenwich Mean Time as
standard and reference
1895 : First street map published in the USA
View on Prime Meridian
at Greenwich
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Historic Overview - 20th Century (1)
1904 : First Radio Navigation- hyperbolic localization using amplitude differences of received signals
1920 : First developments on inertial navigation systems
1948 : Introduction of Standard for Instrument Landing System- introduction by ICAO (International Civial Aviation
Organization)
1957 : First artificial satellite „Sputnik“ launchedby the U.S.S.R.- U.S. researchers calculate position using orbits
and Dopplershift- Origin of Satellite Navigation
1950s : U.S. Navigation System LORAN-C - military use only until 1974, - since 1980 FAA supplementary means for
en route navigation in aviation, now going offline
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Historic Overview - 20th Century (2)
1967 : U.S. Navy Navigation Satellite System Transit operational
- Russian pendant Tsikada also in development
1995 : Navstar Global Positioning System (GPS) fully operational
- Procurement / Development started in 1973 launched by US DOD- 1996 Russian Global Navigation Satellite System (GLONASS)
fully opertional
2000s : Studies on Radio Localization in cellularmobile radio systems
2014/15: European Navigation System GALILEO operational (IOC), FOC 2018
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Search & Rescue
AviationFleed management
Construction
Shipping
Railway Traffic
Tourism
Time synchronization
Road traffic UAVs
Farming
Mobile Comm.and Positioning
Various Navigation Applications …Examples
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Definition - Positioning
Positioning:
Question: Where am I? Where is the object?
The position is determined by coordinates w.r.t. a coordinate system The coordinate system is defined by
– The origin of the coordinate system and– The orientation of the coordinate axis
We can classify positioning into– absolute positioning (position fixing) and– relative positioning (dead reckoning)
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Definition - Self and Remote positioning
Self Positioning:
Cooperative:
Position is determined with help of others mostly infrastructure, e.g. signals transmitted from other stations
Autonomous / Non Cooperative:
Position is determined without the helpof others, e.g. visual or inertialnavigation
Remote Positioning:
Cooperative:
Position is determined by others withthe help of the object to be located, e.g. positioning of GPS satellite
Autonomous / Non Cooperative:
Position is determined by otherswithout the help of the object tolocated, e.g. radar
Question: Who determines the position?
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Definition - Localization
Localization:
Question: Where am I in a topological sense, e.g. geographically?
The position is described in relation to a topography, e.g. a map
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Definition - Navigation
Navigation:
Question: How do I get from one place to another?
Navigation comprises the planning, monitoring and controling of themovement of an object from one place to another.
Origin of „Navigation“– Lat. „Navis“ (Ship) and „agere“ (to act)
Meaning of Navigation in narrower sense:– Determination of position (often also orientation
and velocity) of an object w.r.t. to a reference Navigation usually considers spacious objects
whereas positioning concerns punctiform position determination
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Quality Measures of Navigation Systems
Measures defined in 2001 by U.S. Federal Radionavigation Plan (FRP)
Accuracy
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Quality Measures of Navigation Systems
Accuracy:
Describes the difference („error“) between estimated and trueparameter, e.g. distance between true and estimated position
The accuracy is typically described by statistic means of thedifference („error“), e.g. the standard deviation, variance orconfidence (often 95%)
Confidence means the maximum value of the difference which isnot exceeded with the probability given (here 95%)
Characterize typical behavior of the system in presence of nominal error components
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Quality Measures of Navigation Systems
Measures defined in 2001 by U.S. Federal Radionavigation Plan (FRP)
Accuracy
Integrity
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Quality Measures of Navigation Systems
Integrity:
Capability of a navigation system to warn the user if the system should not be used
Limit risk of abnormal behaviour of the system due to errors resulting from system failures
Typical parameters e.g. Integrity Risk, Alert Limit and Time-to-alert
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Quality Measures of Navigation Systems
Measures defined in 2001 by U.S. Federal Radionavigation Plan (FRP)
Accuracy
Integrity
Continuity
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Quality Measures of Navigation Systems
Continuity:
Capability of a navigation system to offer a navigation service without interrupt during an ongoing operation
Limit risk of losing the service unexpectedly
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Quality Measures of Navigation Systems
Measures defined in 2001 by U.S. Federal Radionavigation Plan (FRP)
Accuracy
Integrity
Continuity
Availability
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Quality Measures of Navigation Systems
Availability:
Percentage of time (probability) for all possible users in the service area in which the navigation service is available
Availability presumes Accuracy + Integrity [+ Continuity]
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Quality Measures of Navigation Systems
Relationship between parameters:
Integrity
Accuracy
Continuity
Availability
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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General Standardisation Organisations: International Organization for Standardization (ISO) American National Standards Institute (ANSI) Comité Européen de Normalisation (CEN)
Application related Standardisation Organisations: International Civil Aviation Organization (ICAO) International Maritime Organization (IMO) International Hydrographic Organization (IHO) National Aeronautics and Space Administration (NASA) European Space Agency (ESA) Russian Space Agency (Roscosmos) European Telecommunications Standard Institute (ETSI)
Further Organizations International Telecommunications Union (ITU) U.S. Federal Aviation Administration (FAA) European Organization for the Safety of Air Navigation (Eurocontrol)
Standardisation Organisations for Navigation
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Summary
History of Navigation: Transition from Observation of Natural Phenomena to Radio based
Technologies Terrestrial and Satellite Based Positioning Importance of Accurate Time for Precise Positioning Manifold Applications of Localization
Definitions: Self and Remote Positioning Localization Navigation
Quality Measures Accuracy Integrity Continuity Availability
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Outline and Structure
1. Introduction
1.1 Historical Overview of Navigation
1.2 Challenges and Applications
1.3 Definitions
1.4. Understanding the Satellite Navigation Principal
2. From Early Days of Satellite Navigation to Today
2.1 Sputnik
2.2 TRANSIT
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Satellite Navigation –How does it work?
Measurement of the time of arrival of the signals from at least four synchronized satellites provide us with (x1,x2,x3,t), additional measurements improve the accuracy and reliability
1 ns corresponds to 30 cm
2
1
3 4
(x1, x2, x3,t)
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Measuring the time of arrival using the receiver’s clock correlation of the received signal with a local copy
finite bandwidth measurements,corrupted by noise and errors
Time of Arrival
delay measured using the receiver’s clock 300m in GPS
satellite signal
local replica(known sequence)
period of sequence (1023 for GPS open signal)
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Informing about the time of transmission using the transmitter's clock
Time of Transmission
encode the information about the clock reading during transmission (navigation message 50 bps)
determine the beginning of the frame with high accuracy
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Pseudorange:
Pseudorange and range are only equal,if propagation speed in medium is close to vacuum andif the clocks of Rx and Tx are perfectly synchronized
Pseudo Range vs. Range
Pseudorange = c ( Time of Arrival (measured with Rx clock)
- Time of Transmission (measured with Tx clock) )
sm103c 8
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Code and Carrier Phase Signal
Start of a subframe, time encoded in the data
signal flow
next subframe, ditto
20 msinformation50 bps=5·101 bps
…..
1 data bit = 20 repetition of the spreading code 300 m
information1 Mcps=1·106 bps
19 cmambiguity!
code bit = chipmodulated on carrier (BPSK)
Carrier1.5 GHz=1.5·109 1/s
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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System Architecture of Global Satellite Navigation Systems
Space Segment
User Segment
Ground Control Segment
Global Navigation Satellite System (GNSS)
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Space Segment
Tasks:
Transmission of navigation signals
Provision of navigation message(e.g. orbit information, time information,corrections,…)
Components:
Constellation of several navigationsatellites (typically 24-30) in medium earth orbit (MEO, typical altitude 19.000-24.000km)
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Tasks: Determination of orbit information and
satellite clocks corrections
Provision of further correction(e.g. Ionosphere, Group delays)
Generation and upload of navigationmessage to satellites
Monitoring of space segment(correctness of navigation signals)
Control of space segment (satellitemaneuvers, house keeping, …)
Components: Global network of monitoring
stations, uplink and TT&Cstations
Control Center(s)
Ground Control Segment
monitoring stations
uplink andTT&C stations
navigation signalcommand signal
TT&C = Telemetry, tracking & command
control center(s)
data exchange
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Tasks: Reception of navigation signals
Determination of pseudoranges
Decoding of navigation messageinformation (orbit, corrections..)
Determination of user position
Components: User navigation receiver (plenty of
different types, form factors, ….)
User Segment
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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0-150 m
Sources of Error in Pseudoranges
satellite orbitsatellite clockand transmitter
multipath
tropospheric delay
receiver
monitoring- ground segment
corrections
45 cm
5-10 cm
2f ~ cm, 1f < 35 m
ionosphericdelay
1.5 ns
23’000 km
70-400 km
0-10 km
<1 km
interference
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Coordinate Systems
Represent the user’s position latitude “easy” longitude (time)
Earth Centered Earth Fixed( zero longitude = Greenwich meridian)
local: East, Nord, Up
Represent the satellite’s orbit Conventional Inertial
Reference System(0 = vernal equinox)
Kepler’s description – two body and gravitation
time!
latitude(parallels)
longitude(meridians)
Hipparchus, 2nd century BC
earth
longitude ofthe
ascending nodeinclination
satellitesorbital plane
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Key Figures
1 second in 100’000 years
50% of a typical bulb
amazing difference inthe orders of magnitude
50 times faster thanPorsche Carrera or ICE
indoor 100-1000 less1/10 [AttoWatts]
Satellite Navigation Prof. Dr. habil. Michael Meurer | Lehrstuhl für Navigation | 21.10.2015
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Summary
Today, positioning is based on the measurement of propagation delays between various satellites and the user.
Extreme constraints on
– system synchronization (sat. vs. syst. time: 1.5 ns)
– satellite orbit determination (45 cm)
– measurement of the time of arrival by correlation (mm-dm)
– estimation of excess delays in the atmosphere (ionosphere and troposphere)
– multipath
Need for an accurate global reference system
Accuracy is not the only criterion: integrity, as well as the availability of accuracy and integrity are additional key elements in many applications