Satellite Navigation Course

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)


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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)


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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


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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.


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Motivation

Space and Navigation systemshave the same relation ship as

Time and Clock

Human beings exist in time and space!


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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


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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


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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


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Who is 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


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Who is DLR ?


Galileo Control Center @ Oberpfaffenhofencontrolling / operation Galileo Constellation


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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


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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


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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


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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


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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


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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


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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


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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]


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Outline and Structure

1. Introduction



1.3 Definitions

1.4. Understanding the Satellite Navigation Principal


2.1 Sputnik

2.2 TRANSIT


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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“


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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)


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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)


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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


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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


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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


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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


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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


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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


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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


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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)


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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?


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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


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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


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Quality Measures of Navigation Systems

Measures defined in 2001 by U.S. Federal Radionavigation Plan (FRP)

Accuracy


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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


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Accuracy

Integrity


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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


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Accuracy

Integrity

Continuity


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Continuity:

Capability of a navigation system to offer a navigation service without interrupt during an ongoing operation

Limit risk of losing the service unexpectedly


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Accuracy

Integrity

Continuity

Availability


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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]


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Relationship between parameters:

Integrity

Accuracy

Continuity

Availability


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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


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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


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Outline and Structure

1. Introduction



1.3 Definitions

1.4. Understanding the Satellite Navigation Principal


2.1 Sputnik

2.2 TRANSIT


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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)


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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)


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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


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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


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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


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System Architecture of Global Satellite Navigation Systems

Space Segment

User Segment

Ground Control Segment

Global Navigation Satellite System (GNSS)


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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)


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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


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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


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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


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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


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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]


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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

Satellite Navigation Course

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