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Jacob CampbellJacob Campbell

Advisor: Maarten Uijt de Haag, Ph D.Advisor: Maarten Uijt de Haag, Ph D.

Presented at:Presented at:

JUP Quarterly ReviewJUP Quarterly Review

Atlantic CityAtlantic City

October 26, 2000October 26, 2000

Issues using Radar AltimetersIssues using Radar Altimetersfor a Real-Time Integrity Monitor for a Real-Time Integrity Monitor

for SVSfor SVS

Issues using Radar AltimetersIssues using Radar Altimetersfor a Real-Time Integrity Monitor for a Real-Time Integrity Monitor

for SVSfor SVS

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• Background

• TAWS vs. SVS

• Terrain Database Integrity

• Integrity Algorithms

• Future Work

OverviewOverviewOverviewOverview

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• Terrain Awareness Warning Systems (advisory only) have been mandated by the FAA

• Significant R&D investment is being made to reduce CFIT» NASA’s Aviation Safety Program

» FAA’s SafeFlight21 Program

» NIMA’s Ron Brown Airfield Initiative

• Shuttle Radar Topography Mission

• Previous work at OU on integrity monitor

• De-classification of the Department of Defense (DoD) digital terrain elevation data (DTED) level I

BackgroundBackgroundBackgroundBackground

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• Generally provides a Plan display

(note: Universal has a perspective display)

• Data Sources» Terrain Database (also can include obstacles)

» GPS for positioning

» Radar Altimeter (GPWS)

» Other Sensors

• Advisory System

Terrain Awareness Warning SystemTerrain Awareness Warning System(TAWS)(TAWS)

Terrain Awareness Warning SystemTerrain Awareness Warning System(TAWS)(TAWS)

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• Provides perspective

view of terrain

• Data Sources» Terrain Database

» GPS

» INS (for attitude)

» Radar Altimeter (used for integrity monitoring)

• Flight Critical System

Synthetic Vision SystemSynthetic Vision System(SVS)(SVS)

Synthetic Vision SystemSynthetic Vision System(SVS)(SVS)

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• Two Parts

» Certify Database is Correct upon CreationCross check different sources?Measurement Verification?

» Certify Data Read has not been corrupted or terrain changed

Database CertificationDatabase CertificationDatabase CertificationDatabase Certification

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• Background

• TAWS vs. SVS

• Terrain Database Integrity

• Integrity Algorithms• Radar Altimeters

• Future Work

Integrity AlgorithmsIntegrity AlgorithmsIntegrity AlgorithmsIntegrity Algorithms

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• Database Profile generated by obtaining terrain height below aircraft from terrain database

• Synthesized Profile generated by GPS Height – Radar Altimeter Height

Database Profile andSynthesized Profile

Database Profile andSynthesized Profile

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GPS Antenna

Radar Altimeter Antenna

Terrain

MSL

a

arl

r

s

s a r l b ni i i ar s si d d e n b ni i i d di ( , )

p s di i i p p pi i i' 1

Absolute Disparity: Successive Disparity:

Map Profile: Sensed (Synthesized) Profile:

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• Test Statistic:

» Scaled Mean Square Difference (MSD) of Absolute and Successive Difference

Current DTED Terrain Avoidance Current DTED Terrain Avoidance Current DTED Terrain Avoidance Current DTED Terrain Avoidance

TnMSD n pad i

i

n

2 2

2

1

1( )

T was found to be a chi-square distribution, with n = degrees of freedom

1111

Problem!Problem!Integrity Threshold ExceededIntegrity Threshold Exceeded

Problem!Problem!Integrity Threshold ExceededIntegrity Threshold Exceeded

• Why?

• GPS Accurate• sub-meter LAAS data used

• sub-meter post processed Ashtech data used

• Database DTED Level 1

• Radar Altimeter

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Radar Altimeter Radar Altimeter Radar Altimeter Radar Altimeter

This is the point the RAwill “sense” during this roll

RiverRiverThis is the point we’ve been using from the DTED to compute the AD

This is the point we’ve been using from the DTED to compute the AD

This is the point the RAwill “sense” if

straight-and-levelThis is the point the

RA will “sense”

A

B

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(m)

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Test Results - 1 Test Results - 1 Database Profile to Runway 16 using DTEDDatabase Profile to Runway 16 using DTED

Test Results - 1 Test Results - 1 Database Profile to Runway 16 using DTEDDatabase Profile to Runway 16 using DTED

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(m)

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Test Results – 2Test Results – 2Database Profile to Runway 16 using NGS DataDatabase Profile to Runway 16 using NGS Data

Test Results – 2Test Results – 2Database Profile to Runway 16 using NGS DataDatabase Profile to Runway 16 using NGS Data

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Radar Altimeter CharacterizationRadar Altimeter Characterization”Spot” Algorithm”Spot” Algorithm

Radar Altimeter CharacterizationRadar Altimeter Characterization”Spot” Algorithm”Spot” Algorithm

From the set of candidate points pick the closest onefor comparison with the database data

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Radar Altimeter CharacterizationRadar Altimeter CharacterizationDatabase Profile to Rwy 16 using the NGS data and the “Spot” AlgorithmDatabase Profile to Rwy 16 using the NGS data and the “Spot” Algorithm

Radar Altimeter CharacterizationRadar Altimeter CharacterizationDatabase Profile to Rwy 16 using the NGS data and the “Spot” AlgorithmDatabase Profile to Rwy 16 using the NGS data and the “Spot” Algorithm

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Radar Altimeter CharacterizationRadar Altimeter CharacterizationT Statistic for Approach to Runway 16T Statistic for Approach to Runway 16

Radar Altimeter CharacterizationRadar Altimeter CharacterizationT Statistic for Approach to Runway 16T Statistic for Approach to Runway 16

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Slant Range StatisticsSlant Range Statistics

r

x

Y

Horizontal Errors in Terrain Map into Slant Range

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But Does All This Give Integrity?But Does All This Give Integrity?

• Some Data Base Errors Could Slip Past

Translation Error

True Position

Displayed Position

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Integrity MonitoringIntegrity Monitoring

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T Statistic (Absolute Disparity) forEntire Search Area

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Translation Error

Integrity MonitoringIntegrity Monitoring

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Forward Looking SensorsForward Looking SensorsForward Looking SensorsForward Looking Sensors

• Purpose

• Search For Significant Terrain Features• Hill Tops

• Search For Man Made Objects• Requires Obstacle Database

• Cell Phone Towers

• High Tension Power Line Towers

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Translation Error

Integrity Monitoring with Forward Looking Radar

Integrity Monitoring with Forward Looking Radar

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Future Work Future Work Future Work Future Work

• Continued Study of Terrain Test Statistics

• Better Model of Radar Altimeter Through use of the Laser Altimeter Data

• Research in the Area of Forward Looking Sensors

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