1. LATMIX Planning Meeting
LIDAR for LATMIX
December 8-9, Seattle, WA
Brian M. Concannon Jennifer E. Prentice
NAVAIR
(301) (301)
Jim Ledwell Gene Terray
WHOI
(508) (508)
Miles Sundermeyer
UMASS, Dartmouth
(508)

2. Lidar 101 Amplitude (dB) Time (depth)
Laser
Receiver
Amplitude (dB)
Backscatter
Less
Turbid
Animated slide showing how the lidar return signal is dependant on the properties of the water. Need to modify to show two slabs of water with different IOP’s and corresponding lidar return signal.
Time (depth)
The slope of the lidar waveform is dependent on the inherent optical properties and is different for different water types.
Bottom
return

3. Lidar Data Acquisition & Processing
Depth (m)
Time or
Distance
Color Coded
Slope vs. Depth
Depth (m)
Amplitude (dB)
A=e-2KsysD
Depth (m)
Ksys (m-1)
Waveform
Slope vs. Depth
Animated slide showing basic processing technique for in-field viewing of data. Color scale for last protion of animation is arbitrary but Ksys = 0.1 = blue and Ksys=0.7=black.

4. Lidar System Flown 2008 and 2009

5. Telescope Modifications for LATMIX
Dye Return
Dichroic Beam Splitter
Lidar Return
Simultaneous collection of Blue backscatter and Green dye fluorescence

6. Lidar Volume Mapping Approaches

7. LATMIX Lidar Vertical Resolution
Altitude T0
f (laser pulse width, system bandwidth, dig sample rate)
Laser pulse width = 10 ns -> 1.1 meter depth in water
System Bandwidth = 100 MHz (log amp, PMT) = 10 ns
Digitizer Sample Rate = 400 MSPS = 2.5 ns per sample
Bottom Line:
Depth Resolution ~ 1meter with 4X oversample
Note: relative depth accuracy ~10 centimeters

8. LATMIX Lidar Horizontal Resolution
f (scan pattern, pulse rate, platform speed, platform altitude)
Scan Pattern = circular cone
Full Angle = 39 deg
Scan Rate up o 15 Hz
Pulse Rate – up to 1700 Hz
Platform Speed = 100 m/s (1 km/10 sec)
Conservative Example:
100 m/s along track
305 m alt
1000 Hz PRF
11.5 Hz scan rate
Swath Width = 216 m
Min Horizontal = 8 m
Min Along Track = 8 m
Notes - back scan fill
- Peak perf ~ 6 m
Across Track Res is
f (scan speed, PRF)
A/C track
Swath Width is
f (scan angle, Alt)
Along Track Res is
f (scan speed, A/C speed)

9. Flight Patterns vs. Time Evolution
Racetrack
9 km/ (100 m/s) = 90 sec = 1.5 min
5.5 km
30 sec leader (3 km)
0.100 m/s x T sec = N km
For T =45 sec:
Whole Pattern = 7 minute
Across track map speed =
1.5 km/hr (20% overlap)
30 sec leader (3 km)

10. Flight Patterns vs. Time Evolution
Dog Bone
5.5 km
30 sec leader (3 km)
100 m/s x T sec = N km
T = 45 sec
Whole Pattern = 9 min
Revisit mid-point every 5 min
Across track map speed = 1.9 km/h
(33% overlap, )
30 sec leader (3 km)
17.5 km/ (100 m/s) = 175 sec = 3.25 min

11. Performance and Flight Limitations
Lidar
Fog, Low Clouds, Rain
Must Monitor Op Area
Aircraft/Crew
Predicted or Actual
Lightning
Strong Turbulence
12 – 14 hour duty day

12. Dye mapping Opportunity Sept 12, 2008
Intensity vs. Position
Dye Returns
Depth vs. Position
Dye Returns
UTC
Equivalent to GPS Time

13. Environmental Transect June 24, 2009
N. Sargasso Sea
Hatteras
Data Start and End
Latitude (deg)

14. 01:24:18 (UTC) End of Transect SE

15. 01:30:35 UTC Southbound Pass

16. 01:38:30 UTC Northbound Pass

17. Lidar Data Analysis Goals
The measured backscatter (480 nm) and fluorescence (~520 nm) intensities will be used to
Map the 3D dye concentration with 5-10 m horizontal and ~1 m vertical resolutions
Study the temporal evolution of the dye patch
Estimate the along- and cross-isopycnal diffusivities
Track the floats and AUV

18. Questions?

19. BACKUP

20. Mapping Floaters and AUV’s
Blue Return ~ E x Area x R( bb)
~ E x 20 m2 x
~ E x 0.01
AUV Return ~ E x Area x R( bb)
~ E x ? m2 x ?
~ E x 0.25 x 0.2
~ E x 0.05
Automating sorting through the data to find 1 shot requites the AUV/floater return look VERY different

21. Mapping Floaters and AUV’s
Lidar will only detect light within it’s scanning, instantaneous FOV
45º LED upward looking
cone of light
LED
- LIDAR can detect W easily
- Ratio of LIDAR Aperture to LED Spot at
325m separation = 10-5
- attenuation in water ~ e-1.5 = 0.22
- LED Power > 0.2 W (515 to 525 nm)
Retro-Reflective Surface
- 0.1 m2 Retro tape on ground required
ND 3 in Rx for 5 m spot at 305 m
- attenuation in water ~ e-3 = 0.05
m retro-tape = easy detection
LED
retro

22. 01:43:45 UTC Eastbound Pass

23. 01:51:53 UTC Westbound Pass

24. Intensity vs. Position Dye Returns
Sept. 12, 2008
Forward
Scan
Aft
Scan

25. Depth vs. Position Dye Returns
Sept. 12, 2008
Depth calculated at 50% rise of max peak
Surface onset calculated at 50% rise of surface flash

26. Light in the Ocean
Basic illustration of the depth at which different colors of light penetrate ocean waters. Longer wavelength light (reds and oranges) is absorbed more quickly than shorter wavelength light (greens and blues).

27. HITS 4.1 All Tanker Types + MerchantsTW