radars pointing rivers water surface velocity & bed profiling

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Radars Pointing Radars Pointing Rivers Rivers Water Surface Velocity Water Surface Velocity & & Bed Profiling Bed Profiling

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Radars Pointing Rivers Water Surface Velocity & Bed Profiling. OUTLOOK. Following monitoring practice in ocean and atmosphere  river monitoring moves toward remote sensing practices - PowerPoint PPT Presentation

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Page 1: Radars Pointing Rivers Water Surface Velocity  &    Bed Profiling

Radars Pointing Radars Pointing RiversRivers

Water Surface Velocity Water Surface Velocity &&

Bed Profiling Bed Profiling

Page 2: Radars Pointing Rivers Water Surface Velocity  &    Bed Profiling

OUTLOOKOUTLOOK Following monitoring practice in ocean and

atmosphere river monitoring moves toward remote sensing practices

USGS has put forth a team (Hydro 21) for remote, non-contact, river monitoring to replace the over 7,000 stream gages

Remote sensing might revolutionize the current multi-task (discharge – velocity – depth - slope) river monitoring practice

Intensive and extensive developments needed to overcome practical implementation

Page 3: Radars Pointing Rivers Water Surface Velocity  &    Bed Profiling

MEASUREMENT CANDIDATESMEASUREMENT CANDIDATESWave-based techniques: electromagnetic radiation

and sound (magnetic and pressure waves): radars, image velocimetry, sonars

http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html

http://www.geocities.com/kbachhuber2000/ems.html

Page 4: Radars Pointing Rivers Water Surface Velocity  &    Bed Profiling

RADARSRADARS

Most extensive tested so far for riverine environment

Wavelenghts from microwaves to radio waves Doppler (coherent) or non-Doppler systems Various configurations Measurement objectives:

– free-surface velocities– bathymetry– stage

Page 5: Radars Pointing Rivers Water Surface Velocity  &    Bed Profiling

OPERATING PRINCIPLEOPERATING PRINCIPLEVelocity: Bragg scattering

Issues:- what represents v?- how to relate v to velocity

in the water column?- how to get the proper free-

surface wavelength (only one detected for a given radar wavelength)

v

f'f

v = fd / (2 cos ), (f d = f-f')

v : water velocity: wave lengthfd : Doppler frequency

KOWACO

Page 6: Radars Pointing Rivers Water Surface Velocity  &    Bed Profiling

OPERATING PRINCIPLEOPERATING PRINCIPLEConfigurations: Monostatic (same antenna for emission

and reception)- Scanning strategy- Assumptions:

- Velocity constant over spot- Streamwise direction known

Page 7: Radars Pointing Rivers Water Surface Velocity  &    Bed Profiling

OPERATING PRINCIPLEOPERATING PRINCIPLEConfigurations: Bistatic (distinct antennas)

Page 8: Radars Pointing Rivers Water Surface Velocity  &    Bed Profiling

RADARS: PROs & CONsRADARS: PROs & CONs

PROs CONs Analytical support Directional velocity measurement Independent of lighting Local (point) measurement Visual output Signal (not intuitive) as output See issues Measurements F(λ, Λ, geometry) Cost

Page 9: Radars Pointing Rivers Water Surface Velocity  &    Bed Profiling

OPERATING PRINCIPLEOPERATING PRINCIPLEGround Penetrating Radar (GPR)

for Bathymetry: reflection of pulsed high-frequency electromagnetic waves

Issues:- Site specific f(surface and

subsurface permittivity)- Performance f(speed of sound in

the measured media, reflectivity, depth of investigation, resolution, interferences, calibration)

http://fate.clu-in.org/gpr.asp?techtypeid=41

Page 10: Radars Pointing Rivers Water Surface Velocity  &    Bed Profiling

GP RADARS: PROs & GP RADARS: PROs & CONsCONs

PROs CONs Analytical basis Complex signal processing Unique for such measurements See issues Visual output Cost

Page 11: Radars Pointing Rivers Water Surface Velocity  &    Bed Profiling

SELECTED RADAR SELECTED RADAR CONFIGURATIONS & CONFIGURATIONS & MEASUREMENTSMEASUREMENTS

Microwave Water Surface Current Meter (KOWACO) UHF RiverSonde Radar (CODAR) Ground Penetrating Radars (MALA GeoScience AB) Flo-Dar (Marsh-McBirney Inc.) DEMO

Page 12: Radars Pointing Rivers Water Surface Velocity  &    Bed Profiling

Microwave Water Surface Current Microwave Water Surface Current Meter Meter (MWSCM-KOWACO)(MWSCM-KOWACO)

Page 13: Radars Pointing Rivers Water Surface Velocity  &    Bed Profiling

MWSCM SPECIFICATIONSMWSCM SPECIFICATIONS Detection Method : Microwave, Doppler effect Frequency : 10 GHz Measurement Range : 0.5~10m/s Measurement Angle :

– Vertical : 20 ~ 45°– Horizontal : 0 ~ 10°

Weight– Antenna : 4.9Kg, Signal processor : 4.2Kg

Page 14: Radars Pointing Rivers Water Surface Velocity  &    Bed Profiling

MWSCM VERIFICATIONMWSCM VERIFICATION

Korea Institute of Construction Technology

0 1 2 3 4 5Carridge velocity (m/s)

0

1

2

3

4

5

Mea

sure

d ve

loci

ty (m

/s)

Velocity Comparison

Vertical angle : 20 deg.

Vertical angle : 30 deg.

Vertical angle : 40 deg.

Vertical angle : 45 deg.

Page 15: Radars Pointing Rivers Water Surface Velocity  &    Bed Profiling

MWSCM MEASUREMENTSMWSCM MEASUREMENTSDaechung Dam

0

1

2

3

4

Velo

city

(m/s

)

0 40 80 120 160 200Distance (m)

20

30

Elev

atio

n (m

)

Taechung Dam

2433 m^3/s(EL. 31.40M)

1960 m^3/s(EL. 30.90M)

1593 m^3/s(EL. 30.24M)

999 m^3/s(EL. 29.42M)

Page 16: Radars Pointing Rivers Water Surface Velocity  &    Bed Profiling

Transmitter

Receiver

RIVERSONDE RADARRIVERSONDE RADAR

Barrick et al. (2003)

Page 17: Radars Pointing Rivers Water Surface Velocity  &    Bed Profiling

GPR GPR USGS Measurements with MALA GPR

Haeni et al. (2003)

Page 19: Radars Pointing Rivers Water Surface Velocity  &    Bed Profiling

Instrument control: FFT of the Doppler shift

Output: channel discharge

DEMODEMOFLO-DAR FLO-DAR (Marsh-McBirney (Marsh-McBirney Inc.)Inc.)

Page 20: Radars Pointing Rivers Water Surface Velocity  &    Bed Profiling

VALIDATIONVALIDATIONFLO-DAR FLO-DAR (Marsh-McBirney (Marsh-McBirney Inc.)Inc.)

1. Best measurements: continuous foam layer (errors up to 10 %)

2. Good results: floating particles (2-3 mm diameter)

3. Poor results: controlled waves (errors up to 40%)

4. Not reliable: natural free surface waviness and lower than 0.5 m/s

Fo a m

So a p Bub b le r

Bub b le s

Fa nFLO -DAR

LDV

Liq uidLSPIV

24c m 79c m

10c m1c m

16.7c m