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Tsunami Detection SystemNick Street, Project EngineerDavid Mould, Presenter
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Agenda
1. Need for Tsunami Detection System2. System Overview3. Tsunami Detection System requirements4. Seabed Unit - Tsunameter5. Surface Unit - Transceiver6. Satellite Modem Link7. Data Examples8. Acoustic telemetry overview 9. Q&A
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Need for Tsunami Detection System
As a result of the Boxing Day 2004 Tsunami the owner of Sonardyne, John Partridge, decided that Sonardyne should look to producing a Tsunami Detection System to help give early warning of a potential life and property damaging event.
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System Overview
The system consists of a seabed pressure monitoring transponder, a surface buoy with a data collection unit that passes the acoustic message to a satellite telephone system and then onwards to the shore base.
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What Do We Need To Detect?
At the Beach easy to detect but to late
Nearing the coast, easy to detect but still to late
In deep water very hard to detect against the natural sea surface movement, but this is the only option that gives enough early warning time
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Tsunami Detection System Requirements
• Pressure sensor• Detection Algorithm• Acoustic Link• Long battery life• Release mechanism• Floatation• Satellite modem
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Tsunami Detection Algorithm
• Based on NOAA algorithm• Predicted pressure calculated from previous 3 hour history, using 10
minutes from each hour (adapted for slow wave)• Detection criteria: C-O > threshold for 2 consecutive samples.
- 3cm used for threshold.• Spike filter – single reading > 10cm ignored• Detection threshold can be changed by acoustic command• An “Event” can be forced or cancelled by acoustic command.
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Tsunami Detection System
1. Need for Tsunami Detection System2. System Overview3. Tsunami Detection System requirements4. Seabed Unit - Tsunameter5. Surface Unit - Transceiver6. Satellite Modem Link7. Data Examples8. Acoustic Telemetry Overview 9. Q&A
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Subsea Unit –Tsunameter
• Based on instrumented survey transponder ‘Compatt 5’• Paroscientific ‘Digiquartz’ pressure sensor• Acoustic data link
- High speed 1kb/s- Forward Error Correction (FEC)- Wideband technology
• Lithium battery pack – 2 year operation• Integral acoustic release• Floatation collar• Thousands of operational deployments • Single pressure housing
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Advantages of a Single Subsea Unit
• No requirement for level seabed • No subsea cables and connectors• Lighter – easier deck handling• In-house control over entire system• Rapid modifications• Simplified testing • Re-use of existing parts• Track record – 1000’s deployments• Proven battery life• Engineering support
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Tsunameter - Sensor Electronics
• Paroscientific “Digiquartz” sensor- 10 000psi (6800m) range- Or 6000psi (4000m) range- Temperature compensated- Extremely high repeatability under
stable thermal conditions• Platinum Resistance Thermometer for
sea water temperature• Release motor • Memory card
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Tsunameter - Sensor Electronics
• Paroscientific “Digiquartz” sensor- 10 000psi (6800m) range- Or 6000psi (4000m) range- Temperature compensated- Extremely high repeatability under stable
thermal conditions• Platinum Resistance Thermometer for
sea water temperature• Release motor • Memory card
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Tsunameter - Sensor Electronics
• Paroscientific “Digiquartz” sensor- 10 000psi (6800m) range- Or 6000psi (4000m) range- Temperature compensated- Extremely high repeatability under stable
thermal conditions• Platinum Resistance Thermometer for
sea water temperature• Release motor• Memory card
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Tsunameter - Sensor Electronics
• Paroscientific “Digiquartz” sensor- 10 000psi (6800m) range- Or 6000psi (4000m) range- Temperature compensated- Extremely high repeatability under stable
thermal conditions• Platinum Resistance Thermometer for
sea water temperature• Release motor • Memory card
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Tsunameter – Deployment in the Bay of Bengal
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Tsunami Detection System
1. Need for Tsunami Detection System2. System Overview3. Tsunami Detection System requirements4. Seabed Unit - Tsunameter5. Surface Unit - Transceiver6. Satellite Modem Link7. Data Examples8. Acoustic Telemetry Overview 9. Q&A
www.sonardyne.com
Surface Unit - Transceiver
• Lightweight - 9kg in water• Low power - 1W at 24V• Wideband signal technology• Integral Li+ battery• Armoured cable to buoy• Optional acoustic baffle• 5km+ acoustic range
> Buoy mounted transceiver with side noise shield that connects to satellite telephone system
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Tsunami Detection System
1. Need for Tsunami Detection System2. System Overview3. Tsunami Detection System requirements4. Seabed Unit - Tsunameter5. Surface Unit - Transceiver6. Satellite Modem Link7. Data Examples8. Acoustic Telemetry Overview 9. Q&A
www.sonardyne.com
Satellite Modem Link
• 2-way communication link• Allows direct control of transceiver• Allows acoustic commands to be
sent to subsea unit - to alter set-up parameters- diagnostics- to Force or Cancel Events
• Not included in Sonardyne scope of supply
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Tsunami Detection System
1. Need for Tsunami Detection System2. System Overview3. Tsunami Detection System requirements4. Seabed Unit - Tsunameter5. Surface Unit - Transceiver6. Satellite Modem7. Data Examples8. Acoustic Telemetry Overview 9. Q&A
www.sonardyne.com
Data Example - Acoustic SMS Messages
• Hourly pressure data – 4 readings averaged over 15 minutes• Hourly status data – battery, sea water temp.• SMS format (Sonardyne Messaging Service) for short text messages:• Identifies data source address• ASCII message delivered securely
SMS:0102,0|061021170000;1,39866;1,40022;1,40157;1,40288
SMS:0102,0|V142,U019,B0,O0,T0,S+1550,SMS:0102,0|061021180000;1,40394;1,40492;1,40569;1,40635
SMS:0102,0|V142,U019,B0,O0,T0,S+1550,
YMDHMS Type 1 (Hourly) P1 P2 P3 P4Pressure Log Status
Tpdr ID F/W Version % Used Battery Alarm Battery On Tilt° Temperature
Up to 128 ASCII characters for customer defined message
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Data Example - Hourly Pressure Messages
Acoustic data hourly message, data points every 15 minutes
34000
35000
36000
37000
38000
39000
40000
41000
42000
18:00 00:00 06:00 12:00 18:00 00:00
Date Time
Raw
abs
. pre
ssur
e (1
0Pa)
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Logged Data Analysis
Simulated Event: measured vs predicted, data from memory card (Difference rebased to 142600)
142000
142100
142200
142300
142400
142500
142600
142700
142800
142900
143000
143100
143200
143300
143400
143500
143600
143700
143800
143900
144000
09:20 09:30 09:40 09:50 10:00
Raw
abs
pre
ssur
e (P
a)
MeasuredPredictedDiff (C-O) detection point
Vertical scale: 1 div ~ 1cm
detection threshold
3 cm
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Data Recovery
t0 t180
Event mode:1x Type 2 message containing 4 x 15s consecutive readings 2 before & 2 during Event)
Time (minutes)
Extended reporting mode:36x Type 3 messages containing10 readings, 30s apart (sent every 5 minutes)
t60 t240
Standard mode:Type 1 message containing 4 readings averaged over 15 minutes sent every hour
t120t-60
Tsunameter: Full Event Cycle
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Event - Data Recovery
Tsunameter: records telemetered during Event
t0
Event mode:4 x 15s readings
Time (minutes)
Extended reporting mode:36 x 10 x alternate 15s readings
t2t-1t-2 t3
A single raw pressure valueOne reading made every 15 seconds
One acoustic message
Key:t1 t5t4 t6 t7 t8 t9 t10 t11 t12
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Acoustic Data from Plymouth Trial – 30 Metres
Tsunami C5 acoustic data: Plymouth 18 - 21 Sept sent via SMS(vertical scale ˜ 1m/div)
34000
35000
36000
37000
38000
39000
40000
41000
42000
18/09/2006 19/09/2006 20/09/2006 21/09/2006 22/09/2006 23/09/2006
Raw
abs
pre
ssur
e (1
0Pa)
Event detection at 01:08 starts rapid data telemetry for 180 minutes
Another detection at 07:07
Unit recovered to surface
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Sea Trial Data – 600 Metres
Sonardyne sea trial - 600m
608600
608700
608800
608900
609000
609100
609200
609300
609400
609500
609600
609700
609800
609900
610000
610100
610200
16/02/2007 17/02/2007 18/02/2007 19/02/2007 20/02/2007 21/02/2007
Abs
olut
e pr
essu
re (1
0Pa
~mm
)
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NIOT Tsunami Buoy Locations
Buoy TB10 which sent the following data
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NIOT Battery Life Test
Sonardyne data: Nicobar earthquake 25/07/07Station: TB10 - 7 deg 1'N 87 deg 4'E Source: 7.08N 92.59E Magnitude 6.2
3851000
3851100
3851200
3851300
3851400
3851500
3851600
3851700
3851800
3851900
3852000
15/07/2007 17/07/2007 19/07/2007 21/07/2007 23/07/2007 25/07/2007 27/07/2007
Abs
pre
ssur
e (1
mm
~ 1
0 Pa
)
Vertical scale ~10cm/div
Real event caused NIOT to be concerned about battery life
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The Event – Two Hours Before
Sonardyne data: Nicobar earthquake 25/07/07Station: TB10 - 7 deg 1'N 87 deg 4'E Source: 7.08N 92.59E Magnitude 6.2
3851560
3851570
3851580
3851590
3851600
3851610
3851620
3851630
3851640
3851650
3851660
3851670
3851680
3851690
21:30:00 21:45:00 22:00:00 22:15:00 22:30:00 22:45:00 23:00:00 23:15:00 23:30:00 23:45:00 00:00:00 00:15:00 00:30:00
Abs
pre
ssur
e (1
mm
~ 1
0 Pa
)
Vertical scale ~1cm/div
The regular 15 minute interval logs that are sent once per hour
Event data takes priority over 15 minute interval logs from the hour in which the event occurs, hence with event just before the hour the ¼, ½and ¾ hour records are not sent
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The Event - Post Event Data
Sonardyne data: Nicobar earthquake 25/07/07Station: TB10 - 7 deg 1'N 87 deg 4'E Source: 7.08N 92.59E Magnitude 6.2
3851550
3851560
3851570
3851580
3851590
3851600
3851610
3851620
3851630
3851640
3851650
3851660
3851670
3851680
3851690
3851700
23:00:00 23:10:00 23:20:00 23:30:00 23:40:00 23:50:00 00:00:00 00:10:00 00:20:00 00:30:00 00:40:00 00:50:00 01:00:00
Abs
pre
ssur
e (1
mm
~ 1
0 P
a)
Vert. scale: ~1cm/div
Data points passed on by NIOT satellite phone system
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The Event – National Media Coverage
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Tsunami Detection System - Requirements
1. Need for Tsunami Detection System2. System Overview3. Tsunami Detection System requirements4. Seabed Unit - Tsunameter5. Surface unit - Transceiver6. Satellite Modem Link7. Data Examples8. Acoustic Telemetry Overview 9. Q&A
www.sonardyne.com
A Tone signal
• Single Frequency
• No modulation
• Defined duration
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A Wideband Signal
• Single carrier Frequency
• Phase modulation to write data onto signal
• Phase changes identify code
• Large numbers of codes can be generated • Not all are suitable for navigation due to correlation properties
• Known as Phase Shift Keying (PSK)
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Correlation Processing - Tone Signal
Incoming Signal
Stored Replica
DetectionThreshold
Correlation Response
ReasonableTiming
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Correlation Processing - Wideband Signal
Signal
Replica
Response
LargePeak
VeryAccurateTiming
DetectionThreshold
Perfect Match
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Robust acoustic data telemetry
• Header wideband signal- correlation gives very low false alarm rate- hence noise immunity- very good timing sync
• Data content encoded using proprietary signals- auto compression of ASCII - Forward Error Correction gives error-free data - or no data
• Not a full modem implementation - inefficient for short packet sizes- introduces latency by using training data
• 5000m achieved – at 25kHz
IRS Wideband Telemetry Data Packet
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Tsunameter - New Developments
• Enhanced pressure sensor measurement electronics and firmware- Continuous power to sensor- Continuous sampling of pressure (15 sec / sample)- NOAA Detection Algorithm applied to samples
• Additional memory card data back-up storage - 2 years into 128MB MMC card
• Lower Frequency band ~15kHz (Prevents clashes with MF LBL and USBL systems)
• 5000m rated housing, (7000m option)
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Acoustic Study for NIOT
• Noise level – at surface & seabed
• Transmission loss:
- signal attenuation in vertical path
- choice of frequency band 15kHz
• Off-vertical corrections for beam pattern
• Off-vertical analysis of ray-bending – using water column profile data
• Equipment detection and transmit levels – factory checked
• Sonar Equation gives the Operating Margin (dB)
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Q & A
Head Office
Sonardyne International Limited T. +44 (0) 1252 872288Blackbushe Business Park F. +44 (0) 1252 876100Yateley, Hampshire, GU46 6GD E. [email protected] Kingdom www.sonardyne.com
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