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Predicting Differential Loran-C
Performance in Boston Harbor
Erik Johannessen
Andre Grebnev
Wouter Pelgrum
32nd International Loran Association
November 3-7, 2003
Context
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Supports on-going LORIPP/LORAPP
evaluations and analyses
Specifically part of a program to prototype
Integrated GPS/Loran for Harbor Entrance and
Approach
Program Participants
32nd International Loran Association
November 3-7, 2003
HEA Receiver Program Scope
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Prototype Integrated Receivers
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Measurement Campaign
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Receiver/Integration Specification
Antenna Design
Cost Study
5 Deliverable Evaluation Units
On-the-Water Data Collection
Reference Station Measurements
Demonstration
Documentation
32nd International Loran Association
November 3-7, 2003
Prototype Integrated Receivers
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Reelektronika develops miniature integrated GPS/Loran-C
receiver as OEM product for NELS (Northwest European Loran System)
Signal Processor
77 x 51 mm
32nd International Loran Association
Front End & ADC
77 x 47 mm
Credit Card
85 x 54 mm
November 3-7, 2003
Prototype Integrated Receivers (cont’d)
Replace MF Beacon Engine with
Loran/GPS/WAAS
Modify H-Field Beacon Antenna To
H-Field Loran
32nd International Loran Association
November 3-7, 2003
Measurement Campaign Overview
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Envisioned as three steps leading to set up
capable of formal demo in DC area
First step local to Megapulse resource
availability
Temporal and spatial decorrelation measured,
also local effects
Differential measurements by tightly time
coupling a reference and rover
Method applicable to all modes
Stored raw sample data permits comparison of
multiple envelope and carrier tracking points
32nd International Loran Association
November 3-7, 2003
Experimental Set-up – Step 1
Reference Station at Megapulse
32nd International Loran Association
Rover Receiving Equipment Suite
November 3-7, 2003
32nd International Loran Association
November 3-7, 2003
32nd International Loran Association
November 3-7, 2003
32nd International Loran Association
November 3-7, 2003
A lovely day for a sail?
32nd International Loran Association
November 3-7, 2003
32nd International Loran Association
November 3-7, 2003
32nd International Loran Association
November 3-7, 2003
32nd International Loran Association
November 3-7, 2003
Reference Station Data
Measurement Date : June 20, 2003
1100-1800 ET
Recorded at Megapulse –(Nan, Sen, Crb, CB shown)
TOA-variations (5 sec integrated)
TOA-variations (60 sec integrated)
0
0
5930X
9960X
-0.1
5930X
-0.05
9960X
-0.2
8970X
-0.1
-0.3
8970X
-0.15
-0.4
5930M
-0.6
us
us
9960M
-0.5
9960M
-0.2
5930M
-0.25
9960W
-0.7
-0.3
9960W
-0.8
-0.9
9960Y
-1
-0.35
9960Y
-0.4
0
50
100
150
200
250
time (minutes)
300
350
5 sec independent samples
32nd International Loran Association
0
50
100
150
200
250
time (minutes)
300
350
Non-moving average of 12 samples
November 3-7, 2003
Reference Station Data (cont’d)
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Note: discrete steps of 20 ns - LPAs or Other??
TOA-variations (60 sec integrated)
TOA-variations (60 sec integrated)
-0.045
-0.27
-0.05
-0.28
-0.055
-0.29
-0.06
9960W
us
us
-0.3
9960X
-0.065
-0.31
-0.07
-0.32
-0.075
-0.33
-0.08
-0.085
-0.34
180
200
220
240
260 280 300
time (minutes)
320
340
360
380
Nantucket – last 3.5 hours
32nd International Loran Association
50
100
150
200
250
time (minutes)
300
350
Caribou – 7 hours, 10nsec/div
November 3-7, 2003
9960Y
Reference Station Data (cont’d)
• Scatter plot created using 7 TOAs, 5 sec integrated/independent
• Repeatability of 7 hour set: 6.5m, 95% and 8.6m, 99%
• Slight offset from mean due to ASF variation
15
60 o
N
Calibrated Loran
Integrated Nav
NovAtel POSA
10
48 o
N
Havre
Fox Harbor
Comfort Cove
Cape Race
Gillette
Caribou
36 o
N
3000
2000
Boise City
1000
Dana
105 o
W
5
Latitude Error (m)
Baudette
Seneca
Nantucket
0
-5
Carolina Beach
Grangeville
Malone
Raymondville
2 4 oN
-10
Jupiter
o
45 W
-15
9 0 oW
-15
75oW
o
60 W
32nd International Loran Association
-10
-5
0
5
10
15
Longitude Error (m)
November 3-7, 2003
Reference Station Data (cont’d)
• Mean of 1st minute used to compensate next twelve 5 sec samples
• Repeatability improves slightly: 6.1m, 95% and 8.2m, 99%
Pseudo-Differential TOA (5 sec integrated, corrected with 60 sec integrated TOA)
0
5930X
15
Calibrated Loran
Integrated Nav
NovAtel POSA
9960X
-0.1
10
-0.2
8970X
-0.4
us
5
Latitude Error (m)
-0.3
-0.5
-0.6
9960M
0
5930M
9960W
-5
9960Y
-10
-0.7
-0.8
-0.9
-1
-15
0
50
100
150
200
250
time (minutes)
32nd International Loran Association
300
350
-10
-5
0
5
10
15
20
Longitude Error (m)
November 3-7, 2003
Reference Station Data (cont’d)
• Mean of ten minutes used to compensate next 120 samples
• Repeatability: 6.2m, 95% and 8.4m, 99%
Pseudo-Differential TOA (5 sec integrated, corrected with 600 sec integrated TOA)
0
5930X
-0.1
9960X
15
Calibrated Loran
Integrated Nav
NovAtel POSA
10
-0.2
8970X
Latitude Error (m)
-0.3
us
-0.4
-0.5
-0.6
-0.7
5
9960M
5930M
0
9960W
-5
-0.8
9960Y
-0.9
-10
-1
0
50
100
150
200
250
time (minutes)
300
350
-10
-5
0
5
10
15
Longitude Error (m)
32nd International Loran Association
November 3-7, 2003
Rover Receiver Results/Issues
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Antenna related
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Receiver related
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Phase error with orientation
Include cable and attenuators as part of antenna
Data grabber worked very well
Need to lose some weight
Vessel related
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Alternator noise
32nd International Loran Association
November 3-7, 2003
Measurements-Step 2
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Currently completing analysis of Step 1
Rover Results
Antenna related issues addressed via
hardware upgrade and compensation in
software
Ship Shape gone to FLA for winter, will
need alternate vessel
Alternatively, SiTex resources in Tampa
Expect to be on water again early December
32nd International Loran Association
November 3-7, 2003
Summary
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Reference station and Rover data collection
systems useful for post processing
High update rate of differential correction did
not significantly improve position fix
Vessel related issues need resolution
Measurement campaign has been critical input
to integrated receiver design
32nd International Loran Association
November 3-7, 2003