Loran Integrity & Performance Panel (LORIPP)

Loran Integrity Performance Panel

Loran Integrity & Performance Panel (LORIPP)

Per Enge, Stanford University, November 2003

Based on the work of: Federal Aviation Administration, U.S. Coast Guard,

Peterson Integrated Geopositioning, Booz Allen Hamilton, Ohio University,JJMA, ITT, University of Wales, Reelektronika & Stanford University

But the opinions may be mine alone & and the mistakes certainly are!

Loran Integrity Performance Panel 2

RNP 0.3 Requirements

Performance Requirement Value

Accuracy (target) 307 meters

Monitor Limit (target) (HAL) 556 meters

Integrity • for all users in the coverage area (cannot

average Boulder against Colorado Springs)• at all times (cannot average solar peak

against quiet times)• under all conditions (in the presence of

hazards)

10-7/hour

Time-to-alert 10 seconds

Availability at primary or alternate airport (minimum/target)

99.9/ 99.99%

Continuity (minimum/target) 99.9/ 99.99%

Integrity Hazards(from Sherman Lo)

TransmitterBias& Jitter

SkywaveInterference

Atmospheric Noise

Propagation Prediction Errors

Local Noise, P-static,Receiver Noise & Bias

LORIPP work is organized around these hazards with a system engineering group predicting coverage.


10-7?10-7 means:• Use the best available engineering to think

through the corner cases. • Find the data that describes the hazard.• If the right data does not exist, collect some. • Design monitors to address any real integrity

issues.• Remember, over design hurts continuity,

availability and coverage.


Error Bounds, Not Accuracy

One or more cycle errors:• Envelope TOA at short ranges• Residuals test at long ranges

2

All cycles correct, but

fails to overbound the true error.

i i i i i ii i i

HPL K K K

Prob(HPE > HPL) < 10-7 per hour

are unbiased

& independent:i are completely

correlatedi are potentially

correlated or biasedi

transmitter

receiver noise & RFI

temporal ASF residual of temporal ASF

spatial ASF


Integrity Analysis

• is best taught by example.

• My favorite example (hazards) are: evil waveforms for GPS early skywave for Loran remember these are only two examples from two

long hazard lists.


DGPS Position Error Measured by Trimble at the 1993 Oshkosh Air Show

SV19 Visibility Period

Alt

itu

de

(met

ers)

Local time of day19 0 5 10 15

Differential vertical errorup to 8.5 meters


C/A and P(Y) Measurement from Camp Parks


Modeling Evil Waveforms(from Eric Phelts)

-1.5 -1 -0.5 0 0.5 1 1.5

0

0.2

0.4

0.6

0.8

1

Correlation Peaks

Code Offset (chips)

Nor

mal

ized

Am

plitu

de0 1 2 3 4 5 6

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

C/A PRN Codes

Chips

Vol

ts

1/fd


Signal Quality Monitoring(from Eric Phelts)

SQM2b

SQM2b E-L Spacings:

0.1 chips*

0.15 chips

0.2 chips

Spacing (chips)

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

0

0.2

0.4

0.6

0.8

1

48 Correlator Receiver Spacings

Nor

mal

ized

Mag

nit

ud

e


WAAS Safety Processor

WREs, level D

SV orbitdetermination& corrections

Iono.correct.& GIVE

UDRERange

DomainPositionDomain

+

CNMP

UDRE

+ +

+ +

Safety ProcessorDO 178 level B

L1/L2Biases

GIVE

Corrections ProcessorDO 178, level D


Error Bounds, Not Accuracy(from Sherman Lo)

LORAN WAAS with Latency Removed


Back to Loran – Early Skywave

0 10 20 30 40 50 60Timeus1.5

1

0.5

0

0.5

1

naroL

tnerruCGroundwave and Early Skywave


ECD Perturbations at Fairbanks(from Bob Wenzel)

7960-Z ECD at Fairbanks 11-12 January 2002

-0.5

0

0.5

1

1.5

2

2.5

11.65 11.7 11.75 11.8 11.85 11.9 11.95 12 12.05 12.1

Large solar proton event on Jan. 10

time in days UT (n.0 is early afternoon on n-1 in Western Alaska)


TD Perturbations at Fairbanks(from Bob Wenzel)

7960-Z TD at Fairbanks 11-12 January 2002

49922.65

49922.7

49922.75

49922.8

49922.85

49922.9

49922.95

11.65 11.7 11.75 11.8 11.85 11.9 11.95 12 12.05 12.1

300

nsec

time in days UT (n.0 is early afternoon on n-1 in Western Alaska)


Previous plots blown up

Caribou (9960W) to Sandy Hook 463NM or

857 km

from Bob Wenzel

7960-Z ECD at Fairbanks 10-11 January 2002

0

0.5

1

1.5

2

2.5

10.65 10.75 10.85 10.95 11.05 11.15 11.25 11.35 11.45

9960-W ECD at Sandy Hook January 2002

-1.5

-1

-0.5

0

0.5

1

10.65 10.75 10.85 10.95 11.05 11.15 11.25 11.35 11.45


Monitor Using 228 Paths < 900 NM(from Ben Peterson)

-130 -120 -110 -100 -90 -80 -70 -60 -50

25

30

35

40

45

50

55

+ Caribou

+ Nantucket

+ Cape Race

+ Fox Harbor+ Williams L

+ Shoal Cove

+ George

+ Port Hardy

+ Malone + Grangevlle

+ Raymondvll+ Jupiter

+ Carolina B

+ Havre + Baudette

+ Boise City

+ Gillette

+ Dana + Fallon + Middletown

+ Searchlght

+ Las Cruces

+ Seneca

+ Comfort Cv

+ Point Pinos

+ Point Cabrl + Grand Junct

+ Bismarck + Spokane

+ Sandspit

+ Whidbey Is.

+ Cape Eliz

+ Montague

+ St Anthony

+ Red Head

+ Mayport + New Orleans

+ Destin

+ Dunbar For

+ Plumbrook

+ Little Rock

+ Midland

+ Sandy Hook


Early Skywave Cures

• Monitor at LorStas and SAMs (not at airports!)

• Range limits• Sample earlier (at 20 or 25 microseconds) &

maybe speed the rise time of the pulse.• Channel sounding pulse• Receiver autonomous detectionSee talks by Peter Morris, Bob Wenzel, Frenand

Le Roux & Ben Peterson for much more.


Summary10-7 means:• Use the best available engineering to think through the

corner cases. • Find the data that describes the hazard.• If the right data does not exist, collect some. • Design monitors to address any real integrity issues.• Remember, over design hurts continuity, availability and

coverage.For Loran• We are well underway.• We have the right people, working the right issues.• But it is a big job


Backup Viewgraphs


Major Hazards

1. Temporal Variations of Groundwave including ASF, ECD and SS

2. Spatial Variations of ASF, ECD & SS3. Weather related noise (p-static & atmospheric)4. Early skywave5. Aircraft dynamics6. Man-made RFI7. Transmitter Hazards

LORIPP work is organized around these hazards with a system engineering group predicting coverage.


-15 -10 -5 0 5 10 1510

-9

10-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

SNR = 6dB

SNR = -6dB

Probability density of TOA for average over 500 pulses

usec relative to selected zero crossing

Typical Distributions of TOA Measurement(from Ben Peterson)

Prob

abil

ity

Den

sity

of

TO

A

Accuracy = fn(Phase

uncertainty)

Pcycle error = fn(Envelope uncertainty)

Blue - Low SNR, Red - High SNR


Threat Flow from GPS Work

Ground controlsegment• upload

GPSsatellite• nav. message• signal dist.

ionosphere& troposphere

Airborneradioenviron.• RFI• multipath

Groundradioenviron.• RFI• multipath

Ref. rcvr.• Level D code• cycle slips

Faultdetection

Databroadcast

Datafaults

Airbornercvr.

Airbornefault

detection


Monitor Performancenominalprob. densityfunction

faultedprob. densityfunction

Pr(false alarm)

Pr(miss detect)


Simulation Data for Locus LRS IIID (from Bob Wenzel)

Loran Integrity & Performance Panel (LORIPP)

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