K-meter Survey SystemLidar Data

Jennifer Prentice

Dave AlloccaTom Curran

Brian ConcannonAlan Laux

Go forth and collect data

EO and Special Mission Sensors DivAIR-4.5.6 Bldg. 2185 Suite 110022347 Cedar Point RoadPatuxent River, MD 20670-1161301-342-2025PrenticeJE@navair.navy.mil

Mike Contarino

What is ksys?

Ret

urne

d O

ptic

al S

igna

l

Time = Depth

H2OAir

Returned optical power vs. depth is a function of : - system parameters - water IOP’s

• System Attenuation Coefficient• An apparent optical property• Water Clarity

P(d) = AP0 e

-2Ksys d

(n h + d)2

Po, FOV, Div

a, b, c, , n

h

d

Where :A includes system parameter effects, air-water transmission and Po = transmitted powerh = height above surfacen = water index of refractiond = water depth

ksys cLoss is due to a and b

ksys kdKrumboltz

Wide DivNarrow FOV

Wide DivWide FOV

Pencil BeamWide FOV

Three Simple Lidar Cases

ksys aLoss is due to a

Adjustable Iris

PMT

1nm Interference Filter

1nm Interference Filter

Adjustable IrisPMT

Window

LASER

Attenuator

Steering Mirrors

Divergence Lens

.25” AperturePentium IVComputerw ith:GPSDigitizersPitch & Roll

Receiver Lens

Receiver Lens

Adjustable Iris

PMT

1nm Interference Filter

1nm Interference Filter

Adjustable IrisPMT

Window

LASER

Attenuator

Steering Mirrors

Divergence Lens

.25” AperturePentium IVComputerw ith:GPSDigitizersPitch & Roll

Receiver Lens

Receiver Lens

Shipboard System Design Specs:

Div = 3o, CH 1 FOV = 10o, CH 2 FOV = 4o

Dual Independent 4” x 4”, ND of 2.6 to 4Output Power: 100mJ @ 532 nm8nS Pulse Width100Mhz Analog Bandwidth8 bit, 1 GSPS Dual DigitizersPMT Photo Detectors with 10% QEInterference Filters with 4 nm Bandwidth

Shipboard KSS Optical Layout

K-Meter Survey System (KSS)

CH 2

CH 1

0 5 10 15 20 25 30

Depth (m)

LO

G(v

olt

s)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

ks

ys (

/m)

Clean Return

Dirty Return

Clean Ksys

Dirty Ksys

CleanEnroute Sta 2 - 3

DirtySta 13

Lidar Signals for Different Water Types

Comparison of Lidar and In-situ Profile DataShallow Mixed Layer at Station 10

HyCODE 2001 – NAVAIR Station Locations

25,000 Ksys Waveforms Collected On Station and In Transit July 22-25

Typical Sample=

40 waveforms

Waveforms processed to yield an average Ksys point measurement for a given depth range

e.g. (1-15 m)

KSS Transect Data, Stations 2 to 10>500 Ksys Samples

0.170

0.220

0.270

0.320

-73.4 -73.2 -73 -72.8 -72.6 -72.4 -72.2 -72 -71.8 -71.6 -71.4 -71.2

Longitude (deg)

c (

/m)

0.050

0.057

0.064

0.071

a (

/m)

c(532) [Pegau slowdrop]

a(532) [Pegau slowdrop]

0.050

0.100

0.150

0.200

0.250

0.300

Ksy

s (

/m)

Ave. Ksys CH1

Ave Ksys Ch2

Sta Num

34567 28910

CH 2Narrow FOV

CH 1Wide FOV

y = 5.159x - 0.4685

y = 0.4434x - 0.0034

0.000

0.200

0.400

0.600

0.800

1.000

1.200

1.400

1.600

1.800

2.000

0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350 0.400 0.450 0.500

Ksys (/m)

a,

c (

/m)

a(532)

c(532)

Ksys vs c

Ksys vs a

A Quick Look at Ksys vs. a(532) and c(532)(Pegau, SLOWDROP Profiler)

Dr. E. Zege Analytical Lidar Model - KSS-2

Future Work

Science Missions :•Validate the model using in-situ dataSolving the forward problem (IOP inputs gives lidar waveform)

•Reverse problemCan a unique set of IOP’s be derived from a single lidar measurement ?

•Detect, identify and monitor shallow water column structuresFor example: plankton and particle scattering layers

Navy Mission :•Sensor performance predictions (ALMDS = AES1)Generate global maps of water clarity versus season

•Mixed layer detection and mapping

Krumboltz REFERENCE1. H. Krumboltz, “Experimental Investigation of System Attenuation Coefficient for HALS”,,Report No

NADCS0035-30 prepared for Defense Mapping Agency, August 1979.

Zege REFERENCES1. E.P. Zege, A.P. Ivanov, and I.L. Katsev, Image Transfer through a Scattering Medium (Springer- Verlag,

Heidelberg, 1991). 349p.

2. I.L. Katsev, E.P. Zege, A.S. Prikhach, and I.N. Polonsky, “Efficient technique to determine backscattered light power for various atmospheric and oceanic sounding and imaging systems”, JOSA A., 14, 1338-1346, (1997).

3. E.P. Zege, I.L. Katsev, and I.N. Polonsky, “Analytical solution to LIDAR return signals from clouds with regard to multiple scattering”, Appl. Phys., B60, 345-353, (1995).

4. E.P. Zege, I.L. Katsev, and I.N. Polonsky, “Effects of Multiple Scattering in Laser Sounding of a Stratified Scattering Medium. 1. General Theory”, Izv., Atmos. Oceanic Phys., 34, N1, 36-40, (1998).

References