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Frankfurt WAMFrankfurt WAM Examples of multilateration implementation

ICAO Seminar on the Implementation of Aeronautical Surveillance and Automation Systems in the SAM Region

San Carlos de Bariloche 6San Carlos de Bariloche 6--8 Decembre 20108 Decembre 2010

New Surveillance Technologies in ATM

Surveillance Technologiesdistributed

cooperativecooperativeindependentnon-

centralised

passive

PSR SSR ADS-BADS-C

1090 ES

UAT

Radar MultilaterationADS MSPSR

PCL MSPSR

Mode A/C/S

Mode A/C

TMA

Airport

dependent independentcooperative

active passiveactive

passive / active

2 Air Operations

VDL-4 WAMcooperativepartially dependent

non-cooperative

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Fundamental Principle of Multilateration

Transponder Reply or Mode S quitter1

Aircraft transponders reply to interrogations from SSR

ltil t ti t

Airport Multilateration (MLAT)Wide Area Multilateration (WAM)

MLAT/WAM CPS

2

Multilateration Ground Stations

(GS)

3

or multilateration systems, and emit unsolicited

squitters/extended squitters

4

calculates surfaces of constant time

difference

Signals received and time stamped

by Ground Stations

3 Air Operations

System Output:Aircraft reports Surveillance

Data Processor

Ground communications

networkATC

Display System

Track reports

Multilateration measures Positions

Multilateration Central

Processing Station (CPS)

Multilateration Basics

Time of Arrival in B: TOA2

A and B are a pair of Ground Stations receiving both a signal from an aircraft.

The Time of Arrival TOA of the signal is measured by

A1

R 2=

c • T

OA 2

Time of Arrival in B: TOA2

A and B are a pair of Ground Stations receiving both a signal from an aircraft.

The Time of Arrival TOA of the signal is measured by

A1

R 2=

c • T

OA 2

Time of Arrival in B: TOA2

At a given time, the Aircraft is on the locus of points having the distance R2 - R1constant:

R2 - R1 = c • (TOA2 - TOA1)

A1

R 2=

c • T

OA 2

R2 - R1 = c • (TOA2 - TOA1) Time of Arrival in B: TOA2

At a given time, the Aircraft is on the locus of points having the distance R2 - R1constant:

R2 - R1 = c • (TOA2 - TOA1)

A1

R 2=

c • T

OA 2

R2 - R1 = c • (TOA2 - TOA1)

1 2

Time of Arrival in A: TOA1

g yeach Ground Station.

The time differenceTOA1-TOA2 corresponds tothe distance differenceR2 - R1 = c • (TOA2 - TOA1)

R1 =

c • T

OA1

Time of Arrival in A: TOA1

g yeach Ground Station.

The time differenceTOA1-TOA2 corresponds tothe distance differenceR2 - R1 = c • (TOA2 - TOA1)

R1 =

c • T

OA1

Time of Arrival in A: TOA1

This is a hyperbola (curve in red).

R1 =

c • T

OA

Time of Arrival in A: TOA1

This is a hyperbola (curve in red).

R1 =

c • T

OA

Time of Arrival in B: TOA2

A third station in C givestwo more differences

R

Time of Arrivalin C: TOA3

R 2=

c • T

OA 2

Time of Arrival in B: TOA2

A third station in C givestwo more differences

R

Time of Arrivalin C: TOA3

R 2=

c • T

OA 2

3Typical Accuracy Distribution from Theory

worstworst

4 Air Operations

Time of Arrival in A: TOA1

R2 - R1 = c • (TOA2 - TOA1)R2 - R3 = c • (TOA2 - TOA3)R1 - R3 = c • (TOA1 - TOA3)

and thus two morehyperbolas follow.

The aircraft can be locatedat the intersection(s) of thehyperbolas

R3 = c • TOA

3

R 2

R 1=

c • T

OA 1

Time of Arrival in A: TOA1

R2 - R1 = c • (TOA2 - TOA1)R2 - R3 = c • (TOA2 - TOA3)R1 - R3 = c • (TOA1 - TOA3)

and thus two morehyperbolas follow.

The aircraft can be locatedat the intersection(s) of thehyperbolas

R3 = c • TOA

3

R 2

R 1=

c • T

OA 1

bestbest

worstworstworst

3

MLAT/WAM System Block diagram

SCU: System Communication Unit

5 Air OperationsAir Systems Division5

Flexible and scalable network centred Architecture

MAGS WAM: DFS PAM Frankfurt

Wide Area Multilateration (WAM) System,Terminal Area Multilateration System,Airport Surface Multilateration System

Frankfurt Terminal Area (120 NM x 80 NM)

Frankfurt/Hahn Airport

Coverage Requirements

Among the heaviest 1090 MHz radio load in the world (according to FAA)

Frankfurt/Main Airport

6 Air Operations

Coverage Simulations Link Budget Models

4

Sites selection

Stepwise process based upon:Detailed visual and graphical topography analysis Computer simulations of the multilateration performance.A series of site surveys and succeeding discussions with DFS

blue = GSR sites (receive function

7 Air Operations

only). red = GST sites (receive/transmit function).

All GST sites are acting as time calibrators and interrogators.

Special Considerations for Multilateration Systems

Geometry of Ground Station Sites and Target : DOPCommon GS coverage required : min 3 GS for 2D, min 4 GS for 3D Good GS constellation required

Synchronisation accuracy Stable and precise common GS time base required

Line of sight restrictionsSufficiently strong signals required (Time of Arrival (TOA) accuracy corresponds to S/N (strong signals = good TOA, weak signals = bad TOA)

Potential obstacles for signal propagation (e.g. terrain, buildings...)Multipath processing required (Wrong TOA, e.g. due to multipath, particularly when no direct signal due to masking)

Availability of the site/building, accessibility

Availability of power supply and data network

8 Air OperationsAir Systems Division8

Availability of power supply and data network

Operational constraints, e.g. obstacle clearance limits

Implementing Multilateration requires both:a good system and good planning!

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Installed WAM Sites

DFS WAM Ground Stations

9 Air Operations

DFS WAM Central Processing Station

Good sites do exist, but...

...many others came before – and they have similar needs

No space on mastTop position occupied Strong transmittersHarmonics close to the 1090 MHz frequency

10 Air Operations

Icefall may impact antenna‘s lifeDaily lightning strikes

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WAM Ground Station Enclosure Types10 HU indoor

24 HU outdoor

24 HU indoor

11 Air Operations

24 HU indoor

WAM : DFS PAM FRA initial test results

PAM FRA Coverage

12 Air Operations

Blue: ADS-BRed: WAM

Technical Display, screenshot with mixed Traffic Situation

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PAM-FRA: WAM Results within Coverage Area

13 Air Operations

Blue: WAM

Technical Display, screenshot with WAM-only Traffic Situation –zoomed-in on coverage area

WAM: DFS PAM FRA - a closer look

High flying ADS-B / MLAT targets have excellent match.

Error << 50 m (typically around 20-30 m),

14 Air Operations

Blue: ADS-BRed: WAM

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WAM/MLAT References

Thales WAM ReferencesThales WAM References

DFS PAM Frankfurt•Upper and lower airspace, TMA, CTR, GND

t t i t

Thales Airport MLAT Thales Airport MLAT ReferencesReferences

Lyon St. Exupéry Airport

Ab Dh bi Ai tat two airports

NATS London TMA•Upper and lower airspace, TMA, CTR ?

Afghanistan country-wide WAM•Upper airspace coverage

Abu Dhabi Airport

Taipeh Tayouan Airport

Helsinki Vantaa Airport

Milano Linate Airport

15 Air Operations

Test bed: WAM STR (Stuttgart-Nuremberg Airspace)•Upper and partially lower airspace, GND

Thank YouThank You

Ludmilla GonzalesLudmilla GonzalesBusiness Development Manager

ludmilla.gonzales@thalesgroup.comTel : +33 (0)1 79 61 42 57

Mob : +33 (0)6 75 79 90 09