Transcript PHILLS 1 Total AM Lines - University of California, Santa

LEO 2001 IN SITU DATA
Profiling Optics and Water Return (POWR) Package
Joe Rhea and Gia Lamela
12/28/2001 #1
LEO 2001 IN SITU DATA
Specifics of Data Collected July 22 Through August 2, 2001
1)
Profiling Optics and Water Return (POWR) Package
Instrument
What is measured
Histar
Water Absorption and Attenuation at 103 wavelengths
ac-9 unfiltered
Water Absorption and Attenuation at 9 wavelengths
ac-9 filtered
CDOM Absorption at 9 wavelengths
Hydroscat-6
Backscattering in 6 wavelengths
WetStar
Stimulated Fluorescence (460nm out / 695nm in)
Seabird CTD
Conductivity (Salinity), Temperature, Depth
Water bottles
8 bottles, each 2.5 liters (total 20 liters of water)
2)
Pad Absorption, including Ap, Ad, Aph, and Ag
3)
Chlorophyll concentration derived from both Turner and HPLC
4)
Above-water Rrs (350-850nm) - Collected when sky conditions permitted
5)
Sun Photometer - Collected when sky conditions permitted
6)
Total Suspended Sediments / Laser particle Counter
12/28/2001 #2
LEO 2001 IN SITU DATA
Summary of Data Collected July 22 Through August 2, 2001
Total stations sampled: 32
Item:
Optic Profiles
Rrs
Pad Absorption
Turner [Chl_a]
HPLC [Chl_a]
Sun Photometer
TSS/LPC
12/28/2001 #3
Processed by:
Rhea/Lamela
J. Rhea
G. Lamela
G. Lamela
C. Trees
W. Snyder
M. Sydor
Count:
55
17
23
23
19
19
> 21
Status:
In Progress
Completed
Completed
Completed
Completed
Completed
In Progress
LEO 2001 IN SITU DATA
Rrs Spectra Collected July 22 Through August 2, 2001
0.012
010722a
010723a
010723c
0.010
010723d
010723e
0.008
010725a
010727c
010731a
0.006
010731b
010731c
010801a
0.004
010801b
010801c
0.002
010801d
010802a
0.000
350
12/28/2001 #4
010802b
450
550
650
750
850
010802c
LEO 2001 IN SITU DATA
Station Locations, July 22 Through August 2, 2001
12/28/2001 #5
LEO 2001 IN SITU DATA
Station Locations for Selected Rrs Spectra
12/28/2001 #6
LEO 2001 IN SITU DATA
Selected Rrs Spectra
0.012
0.010
0.008
010723e
0.006
010731b
010801c
0.004
0.002
0.000
350
12/28/2001 #7
400
450
500
550
600
650
700
750
800
850
PHILLS-1 2001 LEO-15 Data Status
Curtiss O. Davis, Jeffrey Bowles & William Snyder
Code 7212
Naval Research Laboratory
Washington, DC 20375
12/28/2001 #8
Data Summary
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Data Collected.
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Data collected 7/22,, 7/23, 7/25, 7/27, 7/28, 7/31, 8/01 and 8/02/2001.
7/23 & 7/25 1.8 meter in-shore survey.
7/27 & 8/02 Hi-Resolution (0.8 m) in-shore survey.
7/31 AVIRIS over-flight.
8/01 Time series (with AVIRIS over-flight).
7/22 & 7/28 Engineering flights with science capability.
Status Summary.
– Data display small (~ 1 pixel) spatial displacement from laboratory
calibration.
– Some (< 1% of total) data contain dropped bands.
– Pre and Post deployment laboratory wavelength calibrations agree, but differ
slightly from flight data.
– Derived reflectance has been compared twice with simultaneous ASD
observations and are in reasonable agreement.
– However, water pixels located next to bright land features display a rising
reflectance at wavelengths greater than 0.7 microns. Likely cause is sensor
internal light scattering.
– Reflectance below 0.7 microns appears to be minimally effected.
– Latitude and longitude positional information available.
12/28/2001 #9
Code 7212 Web Site (rsd-www.nrl.navy.mil/7212).
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Quick-looks available on Code 7212 Web Site (rsd-www.nrl.navy.mil/7212).
– JPEGS of each aircraft scan.
– PowerPoint and Excel files displaying/listing planned scan coordinates.
12/28/2001 #10
Small Spatial Calibration Shift Across the Array
Result of Using Original Calibration Coefficient File
Result of Shifting Original Calibration Coefficient File 1 Spatial Pixel
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The top figure is an RGB calibrated image of the first 150 lines of
Run15Seq03 taken during the morning of 7/31/2001.
The bottom figure is the same scene but with the radiometric calibration
coefficients file shifted by 1 spatial pixel.
12/28/2001 #11
A small (1-2 nm) Wavelength Shift Across the Array
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12/28/2001 #12
The top figure is the oxygen line
of vegetation spectra extracted
from various samples across
run15seq00 taken on 7/31/01 am.
The detector was in low gain.
The bottom figure is averaged
spectra taken from the left,
middle and right third of the same
image.
The change in line shape suggests
that there is a small spectral shift
across the detector array.
The bin width for this data set is
~4.8 nanometers.
The change in line shape suggests
that the spectral shift is probably
1-2 nanometers.
This amount agrees with more
quantitative analysis using
Tafkaa.
Pre and Post LEO-15 PHILLS1 Wavelength Calibrations Agree
But Flight Wavelengths Are Shifted By A Small Amount
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Band #
cal010711 cal010815 Diff
micron micron nm
Tafkaa Offset
nm
10
28
79
91
115
0.427131
0.514701
0.762816
0.821196
0.937957
1.21
2.21
2.66
2.69
3.24
0.426798
0.514426
0.762705
0.821123
0.937961
0.333
0.275
0.111
0.073
-0.004
512 channel linear calibrations were derived for Pre (cal010711) and Post
(cal010815) LEO-15 deployment using Spec_Cal_Peak_Find1.pro.
The wavelength calibrations for the 512 bands were then “collapsed” to
produce 128 band wavelengths using Bin_Wav_Band.pro.
The wavelengths shown above are the bin center wavelengths derived for the
128 bands.
Agreement between the two calibrations appears to be within 0.33 nanometers.
This difference is much smaller than the wavelength offsets derived for
cal010711 using Tafkaa to obtain the best goodness of fit about selected
atmospheric absorption lines for Run15Seq03 on 7/31/01.
12/28/2001 #13
Spectral Stray Light Correction Required
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Scene averaged calibrated spectrum of water image. The different curves
represents a prob512 of 0.0 (black), 1.0 (green) and 1.6 (red) x 10-4 of spectral stray
light. Note that the radiance goes negative for 1.6 x 10-4 (the value used to correct
last years images).
12/28/2001 #14
Data Calibration Procedure
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The PHILLS-1 calibration coefficients file has been derived using preLEO-15 laboratory calibration data.
Observed counts are corrected for spectral stray light using a delta
function scattering approximation with prob512 = 0.96 x 10-4.
128 spectral band data summed to 64 spectral bands to reduce small band
to band calibration systematic effects.
Radiometric calibration coefficients were computed using sample
averaged laboratory wavelength calibration values.
Resultant calibration coefficient file was then linearly “stretched” to
match wavelength shifts computed by Tafkaa for flight data and then
spatially shifted by 1 pixel.
It is this stretched and shifted laboratory calibration coefficient file that is
applied to the spectral stray light corrected flight data to produce the
radiance data.
12/28/2001 #15
Line (Frame) Banding Example (010722 Run05seq05)
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12/28/2001 #16
Streaks are evident in the data, which for
PHILLS-1 are most evident in spectral
band 128.
Inspection of these streaks indicates that
they are properly placed spatially, but
are spectrally shifted by one band.
Inspection of one flight line with 8129
frames indicates that 64 lines are so
shifted.
If this is representative of the rest of the
data, this indicates that 64/8129 lines or
less than 1% of the data have this
problem.
A bad lines mask, identifying the bad
lines, will be distributed with each data
cube.
Sun Photometer Data are Available for Atmospheric Correction
R/V Northstar Sun Photometer 7/31/2001 15:01 - 15:39 GMT
0.25
0.20
-1.7081
Optical Depth
y = 0.0552x
2
R = 0.9663
0.15
0.10
0.05
0.00
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
Wavelength (microns)
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Data are available at 0.440, 0.675, 0.870, 0.936 And 1.020 Microns.
A power law is fit to the data to obtain optical depth at 550 nm.
– Data above 0.9 microns are excluded.
12/28/2001 #17
Sun Photometer Data Summary
Sun Photometer Summary
Date
GMT
 (550 nm)Exponent H2O (cm-2)Photometer
Lat_Deg Lat_Min Long_DegLong_Min Station
7/23/2001 19:46-20:36
0.184
-1.677
2.4 Cal Panel
39
31.074
74
20.235 Cal
17:51-20:07
0.113
-0.778
1.7 R/V Northstar
39 28.3987
74
8.4116 PM5-E
7/25/2001 13:59-14:01
1.013
-0.597
4.1 R/V Northstar
39 25.2385
74 18.0101 AM4-A
7/27/2001 20:08-20:16
0.173
-0.365
1.1 Cal Panel
39
31.074
74
20.235 Cal
20:12-20:29
0.084
0.561
0.8 R/V Northstar
39 31.0825
74 20.1173 FISH-A
7/31/2001 14:00-14:30
0.122
-1.919
1.8 Cal Panel
39
31.074
74
20.235 Cal
14:01-14:39
0.153
-1.708
1.9 R/V Northstar
39 31.0762
74 20.1035 FISH-A
8/1/2001
15:16
0.177
-1.654
2.0 R/V Northstar
39 30.8624
74 14.7774
01-B
16:48
0.146
-2.233
1.8 R/V Northstar
39 31.5163
74 10.9934
02-A
17:56
0.152
-1.766
1.8 R/V Northstar
39 34.8650
74 11.9610
03-A
20:37
0.148
-1.666
1.5 R/V Northstar
39 27.5607
74 14.8117
04-A
8/2/2001
13:34
0.325
-2.170
2.2 R/V Northstar
39 27.4334
74 14.5871
01-A
13:40-14:55
0.257
-2.035
1.9 Cal Panel
39
31.074
74
20.235 Cal
15:37
0.211
-2.069
1.8 R/V Northstar
39 23.9855
74 15.9401
02-A
17:57
0.198
-1.681
1.6 R/V Northstar
39 26.1816
74 18.5462
03-A
Data on 7/31/2001 taken at same location.
Cal Panel Photometer: #3129
R/V Northstar Photometer: #3130
12/28/2001 #18
Great Bay Region Analysis (010731 Run15seq03)
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X(3)
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X(4)
X(2)
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X(1)
12/28/2001 #19
This image was collected at
an altitude of 8500 feet.
The sensor frame rate was
25 fps, data is binned into 64
spectral channels and the
gain was low.
The image is 1000 pixels
wide and 1024 pixels long.
The spatial resolution is 1.8
meters.
The data has been calibrated
using a calibration
coefficients obtained with a
laboratory plaque
calibration setup corrected
for spectral stray light.
“X’s” mark the location of
spectra shown on the
following slides.
7/31/01 Run15seq03 Region #1, #2 Reflectance
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The single pixel Rrs derived from region #1 (S:551,L:985) and region #2
(S:956,L:708) of the PHILLS1 image shown previously. Also shown (as a blue
line) is the smoothed ASD spectrum measured simultaneously from the R/V
Northstar located near region #1. A mid-latitude summer atmospheric model has
been assumed with marine aerosol ( = 0.12), relative humidity of 70% and 2 m/s
wind speed. Water vapor was determined on a pixel by pixel basis.
Agreement between ASD and aircraft derived reflectance is fair to good in the 0.40.7 micron range. However, an excess reflectance is apparent at longer
wavelengths for region #1.
12/28/2001 #20
7/31/01 Run15seq03 Region #3, #4 Remote Sensing Reflectance
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The single pixel Rrs for two other regions in the image are shown. Region #3 was
taken from [S:748,L:262] and region #4 from [S:488,L:838].
Also shown (in blue) for comparison is the ASD reflectance derived for Region #1.
The Region #3 spectrum shows the effect of viewing the bottom through shallow
water.
The region #4 spectrum is for a land pixel and shows the characteristic red edge
rise in reflectance caused by plant material.
12/28/2001 #21
010731 Run15seq03 (996 nm)
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X(1)
12/28/2001 #22
This image shows the relative
reflectance at 996 nanometers.
An equalization stretch has been
applied to the image.
Note the “glow” around the land
features. It is in these regions
that the rise in near-IR
reflectance is most pronounced.
This glow might be caused by
atmospheric scattering or stray
light entering the detector from
inside, or possibly outside, the
instantaneous FOV defined by
the spectrometer slit.
Note that the ASD measurement
#1 shown previously occurred in
a region with no land (that is,
bright) features within the
IFOV.
Latitude and Longitude Information
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Latitude and longitude information can be derived for each pixel in a
scene based on in-flight C-MIGITS data and derived detector offset
information.
Comparison of known and computed positions of manmade features
observed with low altitude data taken on 8/01/2001 were used to derive
the sensor offsets.
These sensor offsets were then used to derive “time offsets” for each of the
other flights. Reasonable (5-10 pixel) RMS positional errors were
obtained.
It is therefore possible to produce latitude and longitude information for
each scene based on the time offsets derived for each flight and the single
set of sensor offset parameters. Positional errors are expected to be on the
order of 10 meters or less for normal flight altitude data.
This positional information will be stored in IGM files that will
accompany any image that we provide and can be used in ENVI to
georectify an image as desired.
12/28/2001 #23
Image Georectification Example
Original Image
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Georectified Image
IGM files will accompany any image that we provide and can be used to georectify
an image as desired. An challenging example is shown above.
It will probably be necessary to “rubber sheet” any georectified image to other
ground truth information if spatial accuracy < 10 meters is desired.
12/28/2001 #24
Products
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For each image sequence requested, the following products will be
provided.
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Radiance and/or Remote Sensing Reflectance (Rrs) data cube.
Band lines mask.
Positional (IGM) file for that data cube.
A land mask file will also be produced if an Rrs file is produced.
We prefer to download data to the user’s FTP site. It may be possible for
a user to download data from our site but NRL security requirements will
need to be met.
We can make CDs of SMALL data sets.
Products will be produced with the best available information available at
the time but will require user feedback to help identify, quantify and
remove any remaining or newly discovered systematic effects.
12/28/2001 #25