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Ocean Remote Sensing Using Lasers Topics: 1.The principles 2.Bathymetry 3.Water column parameters 4.Pollution survey 5.Lidar in space? European Association.

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Presentation on theme: "Ocean Remote Sensing Using Lasers Topics: 1.The principles 2.Bathymetry 3.Water column parameters 4.Pollution survey 5.Lidar in space? European Association."— Presentation transcript:

1 Ocean Remote Sensing Using Lasers Topics: 1.The principles 2.Bathymetry 3.Water column parameters 4.Pollution survey 5.Lidar in space? European Association of Remote Sensing Laboratories Association Européenne de Laboratoires de Télédétection Dubrovnik, Croatia, 27 May 2004

2 Ocean Remote Sensing Using Lasers 1. The principles The electromagnetic spectrum frequency spectral range photon energy wavelength wave- number rays x rays UV VIS IR micro- waves Radar FM AM radio waves Ra dio d etection a nd r anging Radar Li ght d etection a nd r anging Lidar water is transparent org. matter is absorbing

3 Ocean Remote Sensing Using Lasers 1. The principles Range resolution z from with c speed of light What can be measured? Water depth from seabottom reflection substances at the water surface and underwater from backscatter and fluorescence Australian Antarctic Division Lidar in the atmosphere Oceanic Lidar Light sources with short pulses nanosecond pulse lasers Time-resolved signal detection GHz bandwidth detectors

4 Ocean Remote Sensing Using Lasers 1. The principles Lidar equation for receiver power P(z): substances: concentration n efficiency water: m: refractive index c=c ex +c em attenuation coeff. telescope opt. filter detector laser seafloor z = 0 water depth z flight altitude H Oceanic Lidar A homogeneous water column: c=const., =const.

5 Ocean Remote Sensing Using Lasers 2. Bathymetry: water depth sounding Scanning with laser pulses and registration of induced signals Optech Inc., Canada Nautical charts are often based on very old data Until 1997: almost no acoustic data used Since 2002: approx Gbyte/year of acoustic imagery data Nearshore charting with lidar has become fast and reliable Motivation:

6 Ocean Remote Sensing Using Lasers Scanning with laser pulses and registration of induced signals Optech Inc., Canada 2. Bathymetry: water depth sounding Signal echo versus time-of-flight of elastic backscattered light sea surface: IR laser pulse (=1064 nm) seafloor: green laser pulse(= 532 nm) Method:

7 Ocean Remote Sensing Using Lasers Scanning with laser pulses and registration of induced signals Optech Inc., Canada G. Guenther et al., Bathymetry: water depth sounding Signal response function: Surface return Bottom return Signals from the water column

8 Ocean Remote Sensing Using Lasers 2. Bathymetry: water depth sounding G. Guenther et al., 2000 Chart based on 5 overlapping flight tracks

9 Ocean Remote Sensing Using Lasers 2. Bathymetry: water depth sounding Solander Island, New Zealand Optech Inc., Canada Surveying underwater pinnacles

10 Ocean Remote Sensing Using Lasers 2. Bathymetry: water depth sounding sunken cargo vessel 3 m below sea surface Baltic Sea, water depth 25 m Swedish Maritime Administration

11 Ocean Remote Sensing Using Lasers 2. Bathymetry: water depth sounding Looe Key, Florida Optech Inc., Canada Channel through a coral reef

12 Ocean Remote Sensing Using Lasers Looe Key, Florida digital underwater elevation model Optech Inc., Canada 2. Bathymetry: water depth sounding Channel through a coral reef

13 Ocean Remote Sensing Using Lasers 2. Bathymetry: water depth sounding Maximum depth60 m Vertical accuracy± 0.15 m Horizontal accuracy±3 m (DGPS) Pixel distance8 m Operating altitude400 m Scan swath width220 m Operating speed70 m/s Bathymetric Lidar Performance Example: Shoals 1000 Int. Hydrographic Association requirements for nautical charting Vertical accuracy± 0.25 m Small object detection m 3 Small object detection/identification Seafloor classification (sand, mud, gravel, stones, vegetation) Land-water discrimination Near-shore applicability (waves, foam) Safe navigation (shoreline, anchorage, wrecks) Challenges Further reading: G. Guenther et al., EARSeL eProceedings 1, 2001

14 Ocean Remote Sensing Using Lasers wavelength /nm H 2 O Raman scattering proteins Gelbstoffe Chlorophyll pure water absorption coefficient /m f luorescence, typically of North Sea water ex = 270 nm Signal echo versus time-of-flight at higher wavelengths attenuation Raman scattering 3. Water column parameters fluorescence proteins Gelbstoffe plankton pigments Method: depth profiles of substances

15 Ocean Remote Sensing Using Lasers 3. Water column parameters Fluorescence of molecules distance of nuclei energy singlet state S o singlet state S 1 distance of nuclei energy singlet state S o singlet state S 1 triplet state T 1 phosphorescence > 1 ms relaxation : 1 ns µs fluorescence absorption relaxation Fluorescence spectra do not depend on excitation wavelength! intersystem crossing

16 Ocean Remote Sensing Using Lasers 3. Water column parameters Molecular scattering elastic Stokes shiftanti-Stokes shift Rayleigh scatteringRaman scattering Raman spectra preserve the vibrational energy E!

17 Ocean Remote Sensing Using Lasers arb. intensity /nm 3. Water column parameters Water Raman scattering: O HH O HH O HH free molecules: liquid water: arb. intensity From: Schröder M et al., Applied Optics 42(21), , 2003

18 Ocean Remote Sensing Using Lasers 3. Water column parameters The lidar equation water Raman scattering fluorescence fluorescence normalised to Raman scattering

19 Ocean Remote Sensing Using Lasers 3. Water column parameters Onboard ship R/V Polarstern From: Ohm K et al., EARSeL Yearbook Paris, 1998

20 Ocean Remote Sensing Using Lasers 3. Water column parameters wavelength /nm H 2 O Raman scattering proteins Gelbstoffe Chlorophyll pure water absorption coefficient /m f luorescence, typically of North Sea water ex = 270 nm Chlorophyll vs. depth in the Antarctic Ocean arb. units Onboard ship From: Ohm K et al., EARSeL Yearbook Paris, 1998

21 Ocean Remote Sensing Using Lasers Depth Profiling Fluorescence Lidar Performance: Maximum depth: Open ocean100 m Coastal waters m Temperature, salinity Underwater imaging Lidar signal deconvolution Challenges: 3. Water column parameters Underway measurements Maximum depth Chlorophyll20 m Gelbstoffe40 m Water Raman40 m Elastic backscatter60 m Vertical accuracy± 0.15 m Onboard ship

22 Ocean Remote Sensing Using Lasers 3. Water column parameters Lidar signal deconvolution Measured signal: where: instrument response function ideal signal measured signal signal with 0.1% noise, Fourier Transformation signal with 0.1% noise, Richardson-Lucy algorithm From: Harsdorf & Reuter, EARSeL eProceedings 1, 2001

23 Ocean Remote Sensing Using Lasers 3. Water column parameters Airborne 1983 depth profiling at nighttime depth integrating in daylight

24 Ocean Remote Sensing Using Lasers Tidal fronts UV attenuation ex em 344 VIS attenuation ex em 533 gelbstoff flu. ex em 366 chlorophyll flu. ex em Water column parameters Airborne From: Reuter R et al., Int J Remote Sensing, 14: , 1993

25 Ocean Remote Sensing Using Lasers 3. Water column parameters Tidal fronts Airborne gelbstoff fluorescence ex 308 – em 360 From: Reuter R et al., Int J Remote Sensing, 14: , 1993

26 Ocean Remote Sensing Using Lasers red: Gelbstoffe brought to the sea surface by upwelling 3. Water column parameters Canary Islands: wind-induced upwelling trade winds blue: Gelbstoffe bleached by UV From: Milchers et al., 3rd Workshop Lidar Remote Sensing of Land and Sea, EARSeL, 1997

27 Ocean Remote Sensing Using Lasers 4. Pollution monitoring to do:

28 Ocean Remote Sensing Using Lasers wavelength /nm H 2 O Raman scattering proteins Gelbstoffe Chlorophyll pure water absorption coefficient /m f luorescence, typically of North Sea water ex = 270 nm 1.signal loss of water Raman scatter Methods: 4. Pollution monitoring

29 Ocean Remote Sensing Using Lasers wavelength /nm Intensity crude oils wavelength /nm Agrill Auk Brent Intensity refined oils wavelength /nm Diesel Gasoline Reformat Intensity 1.signal loss of water Raman scatter Methods: 2.the fluorescence signature 4. Pollution monitoring From: Hengstermann T & R Reuter, EARSeL Adv Rem Sens, 1, 52-60, 1992

30 Ocean Remote Sensing Using Lasers Airborne maritime surveillance 4. Pollution monitoring approx. 30 litres very light crude

31 Ocean Remote Sensing Using Lasers 3+4. Airborne Depth resolving 40 m Nighttime only Maximum depth20 m Integratingupper 2-10 m Parameters chlorophyll µg/l Gelbstoffecoastal conc. mineral particles mg/l attenuation coeff.c < 10 m -1 oil film thickness µm oil type classes certain chemicals Fluorescence Lidar Performance Challenges Reliable, compact, transportable Affordable Data fusion with other sensor data

32 Ocean Remote Sensing Using Lasers 5. Lidar in space? Rationale: Measures Gelbstoff in the open ocean No ambiguity in coastal waters Verifies oil spills in SAR images Possibly an add-on to atmospheric lidars

33 Ocean Remote Sensing Using Lasers 5. Lidar in space? Atmospheric lidars:LITE

34 Ocean Remote Sensing Using Lasers

35 5. Lidar in space?

36 Ocean Remote Sensing Using Lasers 5. Lidar in space? Atmospheric lidars:LITE Flight from the Atlantic (left) over the Sahara (centre, right)

37 Ocean Remote Sensing Using Lasers 5. Lidar in space? Atmospheric lidars:WALES (Water vApour Lidar Experiment in Space) ESA Living Planet Programme,

38 Ocean Remote Sensing Using Lasers 5. Lidar in space? Radiative transfer simulation From: Bartsch B et al, Applied Optics, 32, , 1993

39 Ocean Remote Sensing Using Lasers 5. Lidar in space? Radiative transfer simulation From: Bartsch B et al, Applied Optics, 32, , 1993

40 Ocean Remote Sensing Using Lasers 5. Lidar in space? Radiative transfer simulation From: Bartsch B et al, Applied Optics, 32, , 1993

41 Ocean Remote Sensing Using Lasers 5. Lidar in space? Radiative transfer simulation From: Bartsch B et al, Applied Optics, 32, , 1993

42 Ocean Remote Sensing Using Lasers 5. Lidar in space? Radiative transfer simulation From: Bartsch B et al, Applied Optics, 32, , 1993

43 Ocean Remote Sensing Using Lasers Measures RM: Laser remote sensing. John Wiley & Sons, New York (1984) Kirk JTO: Light and photosynthesis in aquatic ecosystems. Cambridge University Press, 2nd ed. (1994) Mobley CD: Light and water. Academic Press (1994) Ishimaru A: Wave propagation and scattering in random media. Vol Academic Press (1978) Andrews LC & RL Phillips: Laser beam propagation through random media. SPIE (1998) Various papers from many lidar research groups in EARSeL eProceedings Further reading:


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