Acoustic-Microwave Water Level Acoustic-Microwave Water Level Sensor Comparisons in an Sensor Comparisons in an

Estuarine EnvironmentEstuarine Environment

John D. BoonJohn D. BoonJohn M. BrubakerJohn M. Brubaker

Virginia Institute of Marine ScienceVirginia Institute of Marine ScienceCollege of William and MaryCollege of William and MaryGloucester Point, VA 23062Gloucester Point, VA 23062

OCEANS’08 MTS/IEEE MEETING, QUEBEC, CANADA

Acoustic Sensor Aquatrak 3000 Series

Primary Sensor

NOAA/NOS National Water Level Observation Network (NWLON)

Selected Microwave SensorsSelected Microwave Sensors

Miros Design Analysis Ohmart/Vega Sutron

2 signal types: pulse and frequency modulated continuous wave

Heitsenrether et al., OCEANS’08 MTS/IEEE QUEBEC

Test SetupTest Setup

Heitsenrether et al., OCEANS’08 MTS/IEEE QUEBEC

Microwave Sensor Design Analysis Associates (DAA)

Model H-3611

Virginia Institute of Marine Science (www.vims.edu/tidewatch)

Acoustic

Microwave

STORM TIDE EMERGENCYSTORM TIDE EMERGENCY MANAGEMENT (STEM)MANAGEMENT (STEM) ( (www.vims.edu/tidewatch)

Storm SurgeStorm Surge

Tidal Water LevelsTidal Water Levels

Subtidal Water LevelsSubtidal Water Levels

6-minute data in near real-time6-minute data in near real-time

STORM TIDE EMERGENCYSTORM TIDE EMERGENCY MANAGEMENT (STEM)MANAGEMENT (STEM) ( (www.vims.edu/tidewatch)

Storm SurgeStorm SurgeTidal Water LevelsTidal Water Levels

Subtidal Water LevelsSubtidal Water Levels6-minute data in near real-time6-minute data in near real-time

Tsunami Warning SystemsTsunami Warning Systems1-minute data in near-real time1-minute data in near-real time

HANNA

JAMESTOWN FERRY PIER, VA

Hurricane IKE

Water Level MeasurementsWater Level Measurements Fixed Sampling Interval Fixed Sampling Interval

Noise (Gaussian) + Signal (periodic)Noise (Gaussian) + Signal (periodic)

Water Level MeasurementsWater Level Measurements Fixed Sampling Interval Fixed Sampling Interval

Noise (Gaussian) + Signal (periodic)Noise (Gaussian) + Signal (periodic)

Standard error = Standard error = σσ/√n /√n (moving average)(moving average)

Water Level MeasurementsWater Level Measurements Fixed Sampling Interval Fixed Sampling Interval

Noise (Gaussian) + Signal (periodic)Noise (Gaussian) + Signal (periodic)

Standard error = Standard error = σσ/√n /√n (moving average)(moving average)

More is betterMore is betterInterval doesn’t matterInterval doesn’t matter

Water Level MeasurementsWater Level Measurements Fixed Sampling Interval Fixed Sampling Interval

Noise (Gaussian) + Signal (periodic)Noise (Gaussian) + Signal (periodic)

Standard error = Standard error = σσ/√n /√n (moving average)(moving average)

More is betterMore is betterInterval doesn’t matterInterval doesn’t matter

Energy-Frequency distribution Energy-Frequency distribution (numerical filter) (numerical filter)

Water Level MeasurementsWater Level Measurements Fixed Sampling Interval Fixed Sampling Interval

Noise (Gaussian) + Signal (periodic)Noise (Gaussian) + Signal (periodic)

Standard error = Standard error = σσ/√n /√n (moving average)(moving average)

More is betterMore is betterInterval doesn’t matterInterval doesn’t matter

Energy-Frequency distribution Energy-Frequency distribution (numerical filter) (numerical filter)

Longer is betterLonger is betterInterval mattersInterval matters

Data Collection Rate: 1 sample/sec (Data Collection Rate: 1 sample/sec (1Hz1Hz))

Acoustic Water Level (AWL)Acoustic Water Level (AWL)Aquatrak 3000 NOAA/NOSAquatrak 3000 NOAA/NOS

Data Collection Rate: 1 sample/sec (Data Collection Rate: 1 sample/sec (1Hz1Hz)) Filtering: 181-second Moving AverageFiltering: 181-second Moving Average

Acoustic Water Level (AWL)Acoustic Water Level (AWL)Aquatrak 3000 NOAA/NOSAquatrak 3000 NOAA/NOS

Data Collection Rate: 1 sample/sec (Data Collection Rate: 1 sample/sec (1Hz1Hz)) Filtering: 181-second Moving AverageFiltering: 181-second Moving Average Outliers: Values>3Outliers: Values>3σσ eliminated eliminated

Acoustic Water Level (AWL)Acoustic Water Level (AWL)Aquatrak 3000 NOAA/NOSAquatrak 3000 NOAA/NOS

Data Collection Rate: 1 sample/sec (Data Collection Rate: 1 sample/sec (1Hz1Hz)) Filtering: 181-second Moving AverageFiltering: 181-second Moving Average Outliers: Values>3Outliers: Values>3σσ eliminated eliminated Reporting Interval: 6 minutesReporting Interval: 6 minutes

Acoustic Water Level (AWL)Acoustic Water Level (AWL)Aquatrak 3000 NOAA/NOSAquatrak 3000 NOAA/NOS

Microwave Water Level (mwwl)Microwave Water Level (mwwl)Design Analysis Associates H-3611 Design Analysis Associates H-3611

Data Collection Rate: 1 sample/minuteData Collection Rate: 1 sample/minute

Microwave Water Level (mwwl)Microwave Water Level (mwwl)Design Analysis Associates H-3611 Design Analysis Associates H-3611

Data Collection Rate: 1 sample/minuteData Collection Rate: 1 sample/minute Filtering: Finite Impulse Response (FIR)Filtering: Finite Impulse Response (FIR)

Microwave Water Level (mwwl)Microwave Water Level (mwwl)Design Analysis Associates H-3611 Design Analysis Associates H-3611

Data Collection Rate: 1 sample/minuteData Collection Rate: 1 sample/minute Filtering: Finite Impulse Response (FIR)Filtering: Finite Impulse Response (FIR) Outliers: None removedOutliers: None removed

Microwave Water Level (mwwl)Microwave Water Level (mwwl)Design Analysis Associates H-3611 Design Analysis Associates H-3611

Data Collection Rate: 1 sample/minuteData Collection Rate: 1 sample/minute Filtering: Finite Impulse Response (FIR)Filtering: Finite Impulse Response (FIR) Outliers: None removedOutliers: None removed Reporting Interval: 6 minutesReporting Interval: 6 minutes

},,,...,,...,,{ 65445 tttttt yyyyyyVIMS DATA BLOCK: 12 one-minute water levels

ty 6ty

},,,...,,...,,{ 65445 tttttt yyyyyy

ty 6ty12ty

VIMS DATA BLOCK: 12 one-minute water levels

},,,...,,...,,{ 65445 tttttt yyyyyy

ty 6ty12ty

18ty

VIMS DATA BLOCK: 12 one-minute water levels

},,,...,,...,,{ 65445 tttttt yyyyyy

ty 6ty12ty

18ty

11 minute series

VIMS DATA BLOCK: 12 one-minute water levels

},,,...,,...,,{ 65445 tttttt yyyyyy

11-point Moving Average ?

5111

4111

111

4111

5111 ...... ttttt yyyyy

VIMS DATA BLOCK: 12 one-minute water levels

},,,...,,...,,{ 65445 tttttt yyyyyy

11-point Moving Average ?

5111

4111

111

4111

5111 ...... ttttt yyyyy

554404455 ...... ttttt ygygygygyg

Finite Impulse Response (FIR) Filter with weights ug

VIMS DATA BLOCK: 12 one-minute water levels

},,,...,,...,,{ 65445 tttttt yyyyyy

11-point Moving Average

5111

4111

111

4111

5111 ...... ttttt yyyyy

554404455 ...... ttttt ygygygygyg

uu gg Symmetric filter

Finite Impulse Response (FIR) Filter with weights ug

VIMS DATA BLOCK: 12 one-minute water levels

},,,...,,...,,{ 65445 tttttt yyyyyy

FIR Frequency Response Function*

ns

uu uggG

10 cos2)(

widthfilterns

timeunitcyclesfrequency

)/(

*Fitted using Bloomfield’s least squares approximation

VIMS DATA BLOCK: 12 one-minute water levels

6 minute stop

27 minute pass

88 minute pass

21 minute stop

RMSD = ± 6.7 mm

FindingsFindings

Microwave, acoustic sensors in agreementMicrowave, acoustic sensors in agreement

FindingsFindings

Microwave, acoustic sensors in agreementMicrowave, acoustic sensors in agreement No indication of wave-induced “offset”No indication of wave-induced “offset”

FindingsFindings

Microwave, acoustic sensors in agreementMicrowave, acoustic sensors in agreement No indication of wave-induced “offset”No indication of wave-induced “offset” FIR filter reduces outliers, standard error FIR filter reduces outliers, standard error

FindingsFindings

Microwave, acoustic sensors in agreementMicrowave, acoustic sensors in agreement No indication of wave-induced “offset”No indication of wave-induced “offset” FIR filter reduces outliers, standard error FIR filter reduces outliers, standard error H-3611: low-maintenance, high reliability H-3611: low-maintenance, high reliability

RecommendationsRecommendations

Design a filter – forgo the moving average,Design a filter – forgo the moving average,

standard deviation and throw-out methodsstandard deviation and throw-out methods

RecommendationsRecommendations

Design a filter – forgo the moving average,Design a filter – forgo the moving average,

standard deviation and throw-out methodsstandard deviation and throw-out methods Decide frequency range of interest and Decide frequency range of interest and

design the filter accordingly design the filter accordingly Open ocean comparisons needed Open ocean comparisons needed

Thank you for your attention