Transcript No Slide Title

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
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%
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Integrity Hazards
(from Sherman Lo)
Atmospheric Noise
Skywave
Interference
Local Noise, P-static,
Receiver Noise & Bias
Transmitter
Bias& Jitter
Propagation Prediction Errors

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.
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Error Bounds, Not Accuracy
Prob(HPE > HPL) < 10-7 per hour
All cycles correct, but
One or more cycle errors:
• Envelope TOA at short ranges
• Residuals test at long ranges
HPL  
K
i
2
i
i

K   K
i
i
i
i i
i
fails to overbound the true error.
i are unbiased
 i are completely
 i are potentially
& independent:
correlated
correlated or biased
transmitter
temporal ASF
receiver noise & RFI
Loran Integrity Performance Panel
residual of
temporal ASF
spatial ASF
5
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.
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DGPS Position Error Measured by Trimble
at the 1993 Oshkosh Air Show
Altitude (meters)
Differential vertical error
up to 8.5 meters
SV19 Visibility Period
19
0
5
Local time of day
Loran Integrity Performance Panel
10
15
7
C/A and P(Y) Measurement
from Camp Parks
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C/A and P(Y) Measurement
from Camp Parks
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Modeling Evil Waveforms
(from Eric Phelts)
Correlation Peaks
C/A PRN Codes


1.5
1
Normalized Amplitude
2
1
Volts
0.5
0
-0.5
-1
1/fd
-1.5
-2
0
1
2
3
Chips
4
5
6
0.8
0.6
0.4
0.2
0
-1.5
-1
-0.5
0
0.5
1
1.5
Code Offset (chips)
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Signal Quality Monitoring
(from Eric Phelts)
48 Correlator Receiver Spacings
Normalized Magnitude
1
SQM2b
0.8
0.6
SQM2b E-L Spacings:
0.4
0.1 chips*
0.2
0.15 chips
0.2 chips
0
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
Spacing (chips)
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WAAS Safety Processor
WREs, level D
CNMP
Safety Processor
DO 178 level B
Corrections Processor
DO 178, level D
L1/L2
Biases
Iono.
correct.
& GIVE
UDRE
GIVE
SV orbit
determination
& corrections
UDRE
+
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Range
Domain
Position
Domain
+
+
+
+
12
Error Bounds, Not Accuracy
(from Sherman Lo)
LORAN WAAS with Latency Removed
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Back to Loran – Early Skywave
Groundwave and Early Skywave
Loran Current
1
0.5
0
0.5
1
1.5
0
10
20
30
Time us
40
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50
60
14
ECD Perturbations at Fairbanks
(from Bob Wenzel)
7960-Z ECD at Fairbanks 11-12 January 2002
2.5
2
1.5
1
0.5
0
-0.5
11.65
11.7
11.75
11.8
11.85
11.9
11.95
12
12.05
12.1
time in days UT (n.0 is early afternoon on n-1 in Western Alaska)
Large solar proton event on Jan. 10
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TD Perturbations at Fairbanks
(from Bob Wenzel)
7960-Z TD at Fairbanks 11-12 January 2002
49922.95
49922.85
49922.8
49922.75
300 nsec
49922.9
49922.7
49922.65
11.65
11.7
11.75
11.8
11.85
11.9
11.95
12
12.05
12.1
time in days UT (n.0 is early afternoon on n-1 in Western Alaska)
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7960-Z ECD at Fairbanks 10-11 January 2002
2.5
2
1.5
Previous plots
blown up
1
0.5
Caribou
(9960W) to
Sandy Hook
463NM or
857 km
from Bob
Wenzel
0
10.65
10.75
10.85
10.95
11.05
11.15
11.25
11.35
11.45
11.35
11.45
9960-W ECD at Sandy Hook January 2002
1
0.5
0
-0.5
-1
-1.5
10.85
10.95
Loran 10.65
Integrity10.75
Performance
Panel
11.05
11.15
11.25
17
Monitor Using 228 Paths < 900 NM
(from Ben Peterson)
55
+
Cove
+ Shoal
Sandspit
+ Fox Harbor
+ St Anthony
+ Williams L
+ Port Hardy
50
+ Whidbey Is.
+ Spokane
+ George
+ Havre
+ Comfort Cv
+ Baudette
+ Bismarck
+ Caribou
+ Montague
+ Dunbar For
+ Red Head
+ Cape Race
45
+ Gillette
+ Cape Eliz
+ Seneca
+ Plumbrook
40
+ Dana
+ Fallon
+ Point Cabrl
+ Middletown
+ Grand Junct
+ Point Pinos
+ Boise City
+ Searchlght
35
+ Nantucket
+ Sandy Hook
+ Little Rock
+ Carolina B
+ Las Cruces
+ Midland
+ Malone
+ Grangevlle
+ Destin
+ Mayport
+ New Orleans
30
+ Raymondvll
+ Jupiter
25
-130
-120
-110
-100
-90
-80
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-70
-60
-50
18
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 detection
See talks by Peter Morris, Bob Wenzel, Frenand
Le Roux & Ben Peterson for much more.
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Summary
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.
For Loran
• We are well underway.
• We have the right people, working the right issues.
• But it is a big job
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Backup Viewgraphs
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Major Hazards
1. Temporal Variations of Groundwave including ASF,
ECD and SS
2. Spatial Variations of ASF, ECD & SS
3. Weather related noise (p-static & atmospheric)
4. Early skywave
5. Aircraft dynamics
6. Man-made RFI
7. Transmitter Hazards
LORIPP work is organized around these hazards with a
system engineering group predicting coverage.
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Typical Distributions of TOA Measurement
(from Ben Peterson)
Probability density of TOA for average over 500 pulses
0
10
-1
Probability Density of TOA
10
SNR = -6dB
-2
10
-3
10
Pcycle error =
fn(Envelope
uncertainty)
-4
10
-5
10
-6
10
Accuracy =
fn(Phase
uncertainty)
-7
10
-8
10
SNR = 6dB
-9
10
-15
-10
-5
0
5
usec relative to selected zero crossing
10
15
Blue - Low SNR, Red - High SNR
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Threat Flow from GPS Work
Ground
control
segment
• upload
GPS
satellite
• nav. message
• signal dist.
ionosphere
& troposphere
Airborne
radio
environ.
• RFI
• multipath
Airborne
rcvr.
Airborne
fault
detection
Data
faults
Ground
radio
environ.
• RFI
• multipath
Ref. rcvr.
• Level D code
• cycle slips
Fault
detection
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Data
broadcast
24
Monitor Performance
nominal
prob. density
function
Pr(false alarm)
faulted
prob. density
function
Pr(miss detect)
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Simulation Data for Locus LRS IIID
(from Bob Wenzel)
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