Transcript Document

K-meter Survey System
Lidar Data
Mike Contarino
Go forth and
collect data
Jennifer Prentice
Dave Allocca
Tom Curran
Alan Laux
EO and Special Mission Sensors Div
AIR-4.5.6 Bldg. 2185 Suite 1100
22347 Cedar Point Road
Patuxent River, MD 20670-1161
301-342-2025
[email protected]
Brian Concannon
What is ksys?
•
•
•
Returned Optical Signal
System Attenuation Coefficient
An apparent optical property
Water Clarity
Po, FOV, Div
h
Air
H2O
Time = Depth
d
a, b, c, b, n
Returned optical power vs.
depth is a function of :
- system parameters
- water IOP’s
P(d) =
AP0 e
-2Ksys d
2
(n h + d)
Where :
A includes system parameter effects,
air-water transmission and b(p)
Po = transmitted power
h = height above surface
n = water index of refraction
d = water depth
Three Simple Lidar Cases
Wide Div
Narrow FOV
ksys
c
Loss is due to a and b
Wide Div
Wide FOV
ksys
kd
Krumboltz
Pencil Beam
Wide FOV
ksys a
Loss is due to a
K-Meter Survey System (KSS)
1nm Interference Filter
Receiver Lens
Adjustable Iris
PMT
LASER
CH 2
Divergence Lens
Window
Attenuator
.25” Aperture
Steering Mirrors
CH 1
Receiver Lens
PMT
Adjustable Iris
Pentium IV
Computer
with:
GPS
Digitizers
Pitch & Roll
1nm Interference Filter
Shipboard KSS Optical Layout
Shipboard System Design Specs:
Div = 3o, CH 1 FOV = 10o, CH 2 FOV = 4o
Dual Independent 4” x 4”, ND of 2.6 to 4
Output Power: 100mJ @ 532 nm
8nS Pulse Width
100Mhz Analog Bandwidth
8 bit, 1 GSPS Dual Digitizers
PMT Photo Detectors with 10% QE
Interference Filters with 4 nm Bandwidth
Lidar Signals for Different Water Types
0.8
Clean Return
Dirty Return
Clean Ksys
Dirty Ksys
0.7
0.6
0.4
Clean
Enroute Sta 2 - 3
Dirty
0.3
Sta 13
0.2
0.1
0
0
5
10
15
Depth (m)
20
25
30
ksys (/m)
LOG(volts)
0.5
Comparison of Lidar and In-situ Profile Data
Shallow 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
0.300
Ave. Ksys CH1
Ave Ksys Ch2
Sta Num
Ksys (/m)
0.250
0.200
CH 2
Narrow FOV
0.150
CH 1
Wide FOV
0.100
9
7
8
5
6
4
2
3
0.050
0.320
0.071
0.270
0.064
c(532) [Pegau slowdrop]
a(532) [Pegau slowdrop]
0.220
0.170
-73.4
-73.2
-73
-72.8
-72.6
0.057
-72.4
-72.2
Longitude (deg)
-72
-71.8
-71.6
-71.4
0.050
-71.2
a (/m)
c (/m)
10
A Quick Look at Ksys vs. a(532) and c(532)
(Pegau, SLOWDROP Profiler)
2.000
1.800
a(532)
c(532)
Ksys vs c
Ksys vs a
1.600
1.400
a, c (/m)
1.200
1.000
y = 5.159x - 0.4685
0.800
0.600
0.400
y = 0.4434x - 0.0034
0.200
0.000
0.000
0.050
0.100
0.150
0.200
0.250
Ksys (/m)
0.300
0.350
0.400
0.450
0.500
Dr. E. Zege Analytical Lidar Model - KSS-2
Future Work
Science Missions :
•Validate the model using in-situ data
Solving the forward problem (IOP inputs gives lidar waveform)
•Reverse problem
Can a unique set of IOP’s be derived from a single lidar measurement ?
•Detect, identify and monitor shallow water column structures
For 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
References
Krumboltz REFERENCE
1.
H. Krumboltz, “Experimental Investigation of System Attenuation Coefficient for HALS”,,Report No
NADCS0035-30 prepared for Defense Mapping Agency, August 1979.
Zege REFERENCES
1.
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).