BOREAS RSS-03 Reflectance Measured from a Helicopter-Mounted SE-590
Summary
The BOREAS RSS-03 team collected multiple remotely sensed data sets from the
NASA UH-1 helicopter. This data set includes helicopter-based radiometric
measurements of forested sites acquired during BOREAS made with an SE-590
processed to reflectance factors. The data used in this analysis were collected
in 1994 during the three BOREAS IFCs at numerous tower and auxiliary sites in
both the NSA and the SSA. The 15-degree FOV of the SE-590 yielded a ground
resolution of approximately 79 m at the 300-m nominal altitude.
Note: An extensive helicopter log is available for each IFC. Environmental,
technical, instrumental, and operational conditions are noted for each
observation where applicable. It is strongly recommended that any researcher
doing extended work with this data set obtain a copy of the helicopter log.
Table of Contents
* 1 Data Set Overview
* 2 Investigator(s)
* 3 Theory of Measurements
* 4 Equipment
* 5 Data Acquisition Methods
* 6 Observations
* 7 Data Description
* 8 Data Organization
* 9 Data Manipulations
* 10 Errors
* 11 Notes
* 12 Application of the Data Set
* 13 Future Modifications and Plans
* 14 Software
* 15 Data Access
* 16 Output Products and Availability
* 17 References
* 18 Glossary of Terms
* 19 List of Acronyms
* 20 Document Information
1. Data Set Overview
Radiometer measurements of BOReal Ecosystem-Atmosphere Study (BOREAS) forested
tower and auxiliary sites were taken from a helicopter platform at nadir. The
data were collected in 1994 during the green-up, peak, and senescent stages of
the growing season at numerous tower and auxiliary sites in both the Northern
Study Area (NSA) and Southern Study Area (SSA). The 15-degree field of view
(FOV) of the Spectron Engineering Spectroradiometer (SE-590) yielded an
Instantaneous Field of View (IFOV) of approximately 79 m from the 300 m altitude
typically flown. The SE-590 has a spectral range of 362.7 to 1122.7 nm,
although the "usable" SE-590 range is actually ~400 to 900 nm. The SE-590
bandwidth is ~15 nm and the spacing between bands ~3 nm.
1.1 Data Set Identification
BOREAS RSS-03 Reflectance Measured from a Helicopter-Mounted SE-590
1.2 Data Set Introduction
The helicopter-measured SE-590 radiances and sunphotometer data were used as
input to Version 4.0 of the Second Simulation of the Satellite Signal in the
Solar Spectrum (6S) atmospheric correction software to obtain at-surface
reflectance factors. The data cover the three Intensive Field Campaign (IFC)
periods: 31-May through 10-June (IFC-1), 21-July through 8-August (IFC-2), and
6-September through 16-September (IFC-3).
1.3 Objective/Purpose
The objective of the study was to acquire multispectral, bidirectional
reflectance data of the study sites for assessments of spectral, spatial, and
temporal variability and the impacts of these variabilities on vegetation
indices. A helicopter with a pointable stabilized mount was used to carry a
spectrometer (visible and near-infrared), a spectroradiometer, an infrared
thermometer, and a video camera. An auto tracking sunphotometer was also
deployed to provide data for calculations of irradiance and for atmospheric
correction of the data. The latest available version of the 6S atmospheric
model was used for the calculations of irradiance and for atmospheric
corrections.
1.4 Summary of Parameters
Helicopter-based measurements of at-helicopter radiances and standard
deviations, at-helicopter and at-surface (atmospherically corrected)
reflectances and conditions (surface physical, geometric, and atmospheric) at
the time of the observation.
1.5 Discussion
These measurements were collected as part of the effort to evaluate models that
estimate surface biophysical characteristics from remotely measured optical
signatures.
1.6 Related Data Sets
BOREAS RSS-01 PARABOLA SSA Surface Reflectance and Transmittance Data
BOREAS RSS-02 Level-1b ASAS Imagery: At-sensor Radiance in BSQ Format
BOREAS RSS-03 Reflectance Measured from a Helicopter-Mounted Barnes MMR
BOREAS RSS-03 Atmospheric Measurements from a Helicopter-Mounted Sunphotometer
BOREAS RSS-03 Video Imagery Acquired from a Helicopter Platform
BOREAS RSS-11 Ground Network of Sun Photometer Measurements
BOREAS RSS-12 Automated Ground Sun Photometer Measurements in the SSA
BOREAS RSS-19 1994 Seasonal Understory Reflectance Data
BOREAS RSS-20 POLDER Measurements of Surface BRDF
2. Investigator(s)
2.1 Investigator(s) Name and Title
Dr. Charles L. Walthall, Physical Scientist
2.2 Title of Investigation
Biophysical Significance of Spectral Vegetation Indices in the Boreal Forest
2.3 Contact Information
Contact 1
-------------
Dr. Charles L. Walthall
Physical Scientist
USDA Agricultural Research Service
Remote Sensing and Modeling Laboratory
Beltsville, MD
(301) 504-6074
(301) 504-5031 (fax)
cwalthal@asrr.arsusda.gov
Contact 2
----------------
Sara Loechel
Faculty Research Assistant
Department of Geography
University of Maryland
Beltsville, MD
(301) 504-6823
(301) 504-5031 (fax)
sloechel@asrr.arsusda.gov
Contact 3
-------------
Jaime Nickeson
BORIS Team Representative
NASA GSFC
Greenbelt, MD
(301) 286-3373
(301) 286-0239 (fax)
jaime@ltpmail.gsfc.nasa.gov
3. Theory of Measurements
Radiation striking a vegetative canopy interacts with individual phytoelements
(leaves, stems, branches) and the underlying substrate. The interaction depends
on light quality, radiative form (direct or diffuse), illumination incidence
angle, vegetative component optical properties, and canopy architecture.
Radiation is reflected, transmitted or absorbed.
Reflected radiation measurements were converted to radiances and reflectance
factor. The reflectance factor is the ratio of the target reflected radiant flux
to an ideal radiant flux reflected by a Lambertian standard surface irradiated
in exactly the same way as the target. Reflected radiation from a field
reference panel corrected for nonperfect reflectance and sun angle was used as
an estimate of the ideal Lambertian standard surface (Walter-Shea and Biehl,
1990).
The helicopter missions were designed to provide a rapid means of intensive
spectral characterization of sites and to provide an intermediate scale of
sampling between the surface measurements and the higher altitude aircraft and
spacecraft multispectral imaging devices. The SE-590 instrumentation was chosen
to provide compatibility with surface-based radiometers and Thematic Mapper (TM)
spaceborne sensors. Off-nadir measurements were made as a means of providing
more accurate estimates of hemispherical reflectance and for use with
bidirectional reflectance models.
4. Equipment
4.1 Sensor/Instrument Description
The primary instruments for the BOREAS Remote Sensing Science (RSS)-03
deployment are the SE-590, a Barnes Modular Multiband Radiometer (MMR), a color
Charge-Coupled Device (CCD)-based video camera, and a sun-tracking photometer.
The downward-looking sensor heads, along with a color video camera, are mounted
on an operator-controlled pointable mount that gives variability in the view
zenith and view azimuth directions independent of the heading of the aircraft.
The SE-590 is a field portable, microprocessor-controlled spectroradiometer
developed in the early 1980s. The sensor is a CCD area array detector with a
diffraction grating serving as the spectral dispersion component. The complete
system consists of a microprocessor-based controller connected by cable to two
optical cameras containing the sensors. Lenses are used as collimators for the
optical cameras. Although three different optical heads are available for the
unit, only two can be used at once with a single controller. The primary unit
of interest is the visible/near-infrared (VIS/NIR) optical component, which
employs a silicon sensor and is sensitive to radiation in the 400-nm to 1100-nm
region. The short-wave infrared (SWIR) optical camera uses a lead sulfide
detector with a cooling device for temperature stability and is sensitive to
radiation in the 1100-nm to 2500-nm spectral region. Lenses for 1-degree and
15-degree FOV are available as standard attachments for the VIS/NIR system. A
15-degree FOV lens for the SWIR system was specially fabricated for BOREAS. The
serial number of the instrument used was 2071.
For the BOREAS deployment, a temperature-controlled box was built to counter the
effects of ambient temperature on radiometric response of the VIS/NIR optical
heads. Two VIS/NIR optical heads were housed in the temperature control box for
the final configuration, one with a 1-degree FOV lens and one with a 15-degree
FOV lens. The SWIR optical head was mounted external to the box with a 15-
degree FOV lens. The SWIR head was moved outside the temperature control box to
avoid conflicts between its temperature control system and the system of the
temperature control box. The configuration of the system was such that two of
the three optical heads could be operated at once using a single SE-590
controller. The choice of optical heads (two VIS/NIR or one VIS/NIR and the
SWIR) also required a change in software because the data stream from the SWIR
optical head is different from that of the VIS/NIR optical heads.
For helicopter use, the SE-590 is operated in a slave mode by a dedicated PC
running DOS. The data stream from the SE-590 is communicated via RS-232 cable to
the computer, where it is stored on a hard disk. The unit operates on AC power
available from the aircraft via inverters with self-contained rechargeable
batteries inside the controller available for backup. Sensor integration time
is set automatically via calculations made on a spectral scan prior to each data
collection scan.
The data stream from this device includes digital numbers (DNs) for each
channel, sensor dwell/integration time, date, time, and maximum signal level in
DNs. The PC software adds an operator-specified header and the SE-590 time is
replaced with time from the computer's clock as the data are stored.
4.1.1 Collection Environment
In general, the helicopter was flown during relatively clear days when possible.
Data collection was attempted during conditions of highest possible solar
elevation. All observations were attempted from a nadir observation point and
usually at 300 m above ground level (AGL). Exceptions are noted in the
helicopter log.
4.1.2 Source/Platform
The UH-1 "Huey" series of helicopters has been available as a platform for the
system in many field campaigns. The first 10 years of the system development
and use were with two UH-1B Huey helicopters, while the aircraft used for BOREAS
was a UH-1H model Huey helicopter. Wallops Flight Facility (WFF) changed to the
H-model helicopter because of its increased payload capability, the good
availability of spare parts, and its widespread use by other organizations. The
Bell UH-1H "Iroquois" helicopter, call number N415, was built in 1965 and was
acquired by WFF in 1993. Upon acquisition, the aircraft was slightly modified
for use as a scientific platform.
Helicopter N415 operates with standard or low mount, rear-leaning skids. The
engine is a Lycoming T53/L13, which provides 1,400 shaft HP with 1,290
transmission HP. The fuel capacity provides 2.0 hours of flying time with a 20-
minute fuel reserve under normal modes of operation. The addition of an
auxiliary fuel tank in the port-side door crewman's position provided an
additional 15 minutes of flight time during BOREAS given optimum flight
conditions.
The instrument platform controllers, power supplies and data loggers are mounted
on 54-inch wide, 72-inch-high steel rack mounts fabricated at WFF. Three racks
are situated directly in front of the instrument operators. Seats for the
instrument operators are located across the front of the transmission and main
rotor mast housing. Whenever possible, existing hard points are used for
attaching hardware both internally and externally.
The weight of the entire helicopter system with full instrumentation, full fuel,
and crew members was 9,500 lbs.
4.1.3 Source/Platform Mission Objectives
The helicopter missions were designed to provide a rapid means of intensive
spectral characterization of sites and to provide an intermediate scale of
sampling between the surface measurements and the higher altitude aircraft and
spacecraft multispectral imaging devices. The instruments were chosen to
provide compatibility with surface-based radiometers and TM spacecraft sensors.
Off-nadir measurements were made as a means of providing more accurate estimates
of hemispherical reflectance and for use with bidirectional reflectance models.
4.1.4 Key Variables
Surface reflectance.
4.1.5 Principles of Operation
Computer control of the instruments provides precise, automatic control and
ensures proper timing of data collection. The radiometric instruments are
configured such that all sensors except the photographic camera can be triggered
near-simultaneously with a single computer keyboard keystroke. The command sent
from the keyboard is first sent to the SE-590, then to the A/D systems. Raw
data from each of the instruments are displayed via graphics and tabular
listings on the main computer screen immediately after scanning.
The system is configured for multiple sensor data collection. The MMR, SE-590,
infrared thermometer, autotracking sunphotometer, and video sensor were the
primary payload during BOREAS.
4.1.6 Sensor/Instrument Measurement Geometry
The National Aeronautics and Space Administration (NASA) Goddard Space Flight
Center (GSFC)/WFF helicopter-based optical remote sensing system was deployed to
acquire canopy multispectral data with an SE-590 while hovering approximately
300 meters AGL (Walthall et al., 1996). The 15-degree FOV of the SE-590 yielded
a ground resolution of approximately 79 m at this altitude.
4.1.7 Manufacturer of Sensor/Instrument
SE-590:
Spectron Engineering, Inc.
25 Yuma Court
Denver, CO 80223
(303) 733-1060
4.2 Calibration
4.2.1 Specifications
Spectral Characteristics
SE-590 Range 362.7 to 1122.7 nm
"Usable" SE-590 Range ~400 to 900 nm
Bandwidth ~15 nm
Spacing between bands ~3 nm
Filter function Gaussian (best approximation)
Spectral bands (reported in data set) [nm]:
402.6 405.3 408.0 410.7 413.4 416.1 418.8 421.5 424.2 426.9 429.6
432.3 435.0 437.8 440.5 443.2 446.0 448.7 451.4 454.2 456.9 459.7
462.4 465.2 467.9 470.7 473.4 476.2 479.0 481.8 484.5 487.3 490.1
492.9 495.7 498.5 501.3 504.1 506.9 509.7 512.5 515.3 518.1 520.9
523.7 526.5 529.4 532.2 535.0 537.9 540.7 543.5 546.4 549.2 552.1
554.9 557.8 560.7 563.5 566.4 569.3 572.1 575.0 577.9 580.8 583.7
586.5 589.4 592.3 595.2 598.1 601.0 603.9 606.8 609.8 612.7 615.6
618.5 621.4 624.4 627.3 630.2 633.2 636.1 639.1 642.0 645.0 647.9
650.9 653.8 656.8 659.8 662.7 665.7 668.7 671.6 674.6 677.6 680.6
683.6 686.6 689.6 692.6 695.6 698.6 701.6 704.6 707.6 710.6 713.7
716.7 719.7 722.8 725.8 728.8 731.9 734.9 738.0 741.0 744.1 747.1
750.2 753.2 756.3 759.4 762.4 765.5 768.6 771.7 774.8 777.8 780.9
784.0 787.1 790.2 793.3 796.4 799.5 802.7 805.8 808.9 812.0 815.1
818.3 821.4 824.5 827.7 830.8 834.0 837.1 840.2 843.4 846.6 849.7
852.9 856.0 859.2 862.4 865.6 868.7 871.9 875.1 878.3 881.5 884.7
887.9 891.1 894.3 897.5 900.7
4.2.1.1 Tolerance
None given.
4.2.2 Frequency of Calibration
Radiometric calibration and spectral calibration procedures were performed
before and after the field season to check for changes in sensor radiometric
response. In-field calibration checks were periodically made with a large,
portable integrating sphere system. This sphere was used to calibrate the
airborne instruments on other aircraft and some of the surface-based radiometric
instrumentation.
4.2.3 Other Calibration Information
The question of how to calculate reflectance and correct for atmospheric
influences on airborne data is a challenging issue. The irradiance solution for
the NASA GSFC/WFF helicopter system prior to BOREAS used a second set of
instruments at a centrally located surface-based calibration site. The
instruments were positioned to collect data from a white reflectance panel
(barium sulfate or halon) periodically during the day starting approximately 30
minutes before take-off and stopping 30 minutes after landing.
SE-590 coefficients from the second IFC were calculated in the field.
Conditions did not change much from the beginning of the first IFC until the end
of the last IFC; thus, any of the calibration files are sufficient. The table
of calibration coefficients is output from a software module that supplied
default wavelengths, instead of the exact wavelengths of this instrument. In
practice, they apply to the closest band as given in the SE-590 data set.
---------------------------------------------------------------------------
Wavelength Coefficient (offset of zero) and r2 from regression
---------------------------------------------------------------------------
WAVE COEF r2 WAVE COEF r2
---------------------------------------------------------------------------
401.5 177.877 0.944291
404.3 195.617 0.953270
407.1 212.354 0.959176
409.9 240.441 0.969660
412.7 281.806 0.976171
415.5 329.396 0.983505
418.3 362.033 0.985738
421.1 383.876 0.987624
423.9 406.884 0.989234
426.7 427.885 0.990205
429.5 446.648 0.991536
432.3 454.986 0.992297
435.1 476.587 0.994173
438.0 493.344 0.994685
440.8 511.822 0.995202
443.6 522.264 0.995745
446.4 523.222 0.996257
449.3 519.927 0.996496
452.1 514.144 0.997100
454.9 515.135 0.997069
457.8 507.969 0.997500
460.6 497.376 0.997683
463.5 492.863 0.997825
466.3 492.648 0.997897
469.2 487.060 0.998084
472.0 481.766 0.998269
474.9 478.953 0.998335
477.7 469.324 0.998460
480.6 456.215 0.998530
483.4 447.377 0.998650
486.3 441.005 0.998666
489.2 438.226 0.998647
492.0 441.260 0.998873
494.9 449.451 0.998914
497.8 456.074 0.998928
500.6 459.451 0.999010
503.5 454.181 0.999101
506.4 446.948 0.999090
509.3 440.210 0.999098
512.2 434.007 0.999064
515.1 433.951 0.999189
518.0 434.958 0.999175
520.8 441.795 0.999182
523.7 452.507 0.999234
526.6 461.811 0.999292
529.5 470.346 0.999288
532.4 481.618 0.999324
535.3 485.763 0.999395
538.3 486.522 0.999378
541.2 487.035 0.999372
544.1 481.228 0.999428
547.0 471.868 0.999408
549.9 464.951 0.999458
552.8 456.612 0.999396
555.8 454.872 0.999417
558.7 459.347 0.999432
561.6 467.344 0.999438
564.5 478.390 0.999478
567.5 489.023 0.999479
570.4 496.558 0.999513
573.3 505.392 0.999555
576.3 507.749 0.999551
579.2 504.828 0.999536
582.2 498.284 0.999541
585.1 489.910 0.999553
588.1 480.059 0.999562
591.0 470.787 0.999550
594.0 463.137 0.999574
596.9 457.157 0.999541
599.9 454.545 0.999552
602.9 455.709 0.999546
605.8 458.806 0.999567
608.8 463.753 0.999581
611.8 469.958 0.999595
614.7 477.498 0.999620
617.7 482.404 0.999643
620.7 482.992 0.999660
623.7 480.767 0.999653
626.7 477.871 0.999653
629.6 473.047 0.999663
632.6 464.294 0.999626
635.6 456.748 0.999657
638.6 448.964 0.999647
641.6 442.057 0.999641
644.6 436.108 0.999634
647.6 433.334 0.999650
650.6 426.841 0.999646
653.6 424.231 0.999654
656.6 418.953 0.999628
659.6 417.769 0.999646
662.6 419.553 0.999671
665.7 418.793 0.999664
668.7 418.464 0.999665
671.7 418.540 0.999691
674.7 419.266 0.999675
677.7 414.472 0.999683
680.8 408.282 0.999666
683.8 402.339 0.999697
686.8 394.407 0.999663
689.9 383.948 0.999669
692.9 377.904 0.999662
695.9 371.917 0.999645
699.0 366.746 0.999641
702.0 362.821 0.999658
705.1 364.155 0.999659
708.1 361.576 0.999668
711.2 364.754 0.999664
714.2 370.359 0.999676
717.3 372.134 0.999673
720.4 376.100 0.999686
723.4 381.964 0.999712
726.5 383.358 0.999717
729.6 385.283 0.999733
732.6 387.747 0.999745
735.7 389.354 0.999746
738.8 385.004 0.999735
741.8 379.187 0.999740
744.9 371.829 0.999722
748.0 363.352 0.999721
751.1 354.343 0.999710
754.2 347.139 0.999680
757.3 340.538 0.999703
760.4 336.410 0.999688
763.5 329.992 0.999674
766.6 325.867 0.999690
769.7 319.102 0.999647
772.8 311.361 0.999645
775.9 305.954 0.999653
779.0 299.664 0.999634
782.1 296.534 0.999644
785.2 292.414 0.999615
788.3 288.519 0.999602
791.4 287.586 0.999618
794.5 286.344 0.999597
797.7 284.828 0.999584
800.8 282.668 0.999593
803.9 279.686 0.999592
807.1 277.144 0.999604
810.2 275.932 0.999587
813.3 271.085 0.999558
816.5 266.655 0.999554
819.6 262.913 0.999582
822.7 257.784 0.999555
825.9 250.574 0.999536
829.0 244.616 0.999500
832.2 237.477 0.999479
835.3 228.120 0.999470
838.5 219.124 0.999430
841.6 211.521 0.999392
844.8 204.434 0.999410
848.0 195.746 0.999362
851.1 189.681 0.999332
854.3 187.142 0.999297
857.5 185.715 0.999299
860.6 183.007 0.999294
863.8 181.422 0.999319
867.0 180.540 0.999299
870.2 176.893 0.999283
873.4 171.383 0.999210
876.5 167.060 0.999245
879.7 163.815 0.999196
882.9 160.072 0.999179
886.1 156.389 0.999145
889.3 154.292 0.999143
892.5 151.666 0.999141
895.7 147.559 0.999065
898.9 143.946 0.999039
902.1 138.765 0.998934
5. Data Acquisition Methods
The use of off-the-shelf field instruments aboard airborne platforms is a cost-
effective and efficient approach to assembling a data collection system. The
instruments are generally rugged enough for the harsh operating environment of a
helicopter, provide data comparable to data sets on the surface, and are easy to
use and versatile during operation. The system developed jointly at NASA's GSFC
and WFF uses several widely accepted field-portable radiometric instruments.
The system is configured such that instruments from other investigators can be
deployed on the helicopter with little or no interference with the primary
instrument system. An autotracking sunphotometer system, developed specifically
for use on helicopters, is the newest addition to the system.
The NASA GSFC/WFF helicopter-based optical remote sensing system was deployed to
acquire canopy multispectral data with an SE-590 while hovering approximately
300 meters AGL (Walthall et al., 1996). The 15-degree FOV of the SE-590 yielded
an IFOV at this altitude of approximately 79 m. Observations were made over
various tower and auxiliary sites during all three IFCs.
Measurements were collected as conditions permitted during each IFC. In
general, the helicopter would hover 1-2 minutes for each observation (consisting
of an average number of 20-25 scans).
6. Observations
6.1 Data Notes
See Section 6.2.
6.2 Field Notes
An extensive helicopter log is available for each IFC. Environmental,
technical, instrumental, and operational conditions are noted for each
observation where applicable.
7. Data Description
7.1 Spatial Characteristics
7.1.1 Spatial Coverage
The helicopter visited all of the NSA and SSA tower and category-1 auxiliary
sites.
Each site listed below was observed by this instrument at least once during the
1994 campaign at BOREAS:
--------------------------------------------------------------------------
Site Id Operat�l Longitude Latitude UTM UTM UTM
Grid ID Easting Northing Zone
--------------------------------------------------------------------------
Flux Tower Sites
Southern Study Area:
SSA-FEN-SE501 F0L9T 104.61798W 53.80206N 525159.8 5961566.6 13
SSA-OBS-SE501 G8I4T 105.11779W 53.98717N 492276.5 5982100.5 13
SSA-OJP-SE501 G2L3T 104.69203W 53.91634N 520227.7 5974257.5 13
SSA-YJP-SE501 F8L6T 104.64529W 53.87581N 523320.2 5969762.5 13
SSA-9OA-SE501 C3B7T 106.19779W 53.62889N 420790.5 5942899.9 13
SSA-9YA-SE501 D0H4T 105.32314W 53.65601N 478644.1 5945298.9 13
--------------------------------------------------------------------------
Northern Study Area:
NSA-OBS-SE501 T3R8T 98.48139W 55.88007N 532444.5 6192853.4 14
NSA-OJP-SE501 T7Q8T 98.62396W 55.92842N 523496.2 6198176.3 14
NSA-YJP-SE501 T8S9T 98.28706W 55.89575N 544583.9 6194706.9 14
NSA-BVP-SE501 T4U6T 98.02747W 55.84225N 560900.6 6188950.7 14
NSA-FEN-SE501 T7S1T 98.42072W 55.91481N 536207.9 6196749.6 14
--------------------------------------------------------------------------
Auxiliary Sites
Southern Study Area:
SSA-9BS-SE501 D0H6S 105.29534W 53.64877N 480508.7 5944263.4 13
SSA-9BS-SE501 G2I4S 105.13964W 53.93021N 490831.4 5975766.3 13
SSA-9BS-SE501 G2L7S 104.63785W 53.90349N 523793.6 5972844.3 13
SSA-9BS-SE501 G6K8S 104.75900W 53.94446N 515847.9 5977146.9 13
SSA-9BS-SE501 G9I4S 105.11805W 53.99877N 492291.2 5983169.1 13
SSA-9JP-SE501 F5I6P 105.11175W 53.86608N 492651.3 5968627.1 13
SSA-9JP-SE501 F7J0P 105.05115W 53.88336N 496667.0 5970323.3 13
SSA-9JP-SE501 F7J1P 105.03226W 53.88211N 497879.4 5970405.6 13
SSA-9JP-SE501 G1K9P 104.74812W 53.90880N 516546.7 5973404.5 13
SSA-9JP-SE501 G4K8P 104.76401W 53.91883N 515499.1 5974516.6 13
SSA-9JP-SE501 G7K8P 104.77148W 53.95882N 514994.2 5978963.8 13
SSA-9JP-SE501 G8L6P 104.63755W 53.96558N 523778.0 5979752.7 13
SSA-9JP-SE501 G9L0P 104.73779W 53.97576N 517197.7 5980856.0 13
SSA-9JP-SE501 I2I8P 105.05107W 54.11181N 496661.4 5995963.1 13
SSA-ASP-SE501 B9B7A 106.18693W 53.59098N 421469.8 5938447.2 13
SSA-ASP-SE501 D6H4A 105.31546W 53.70828N 479177.5 5951112.1 13
SSA-ASP-SE501 D6L9A 104.63880W 53.66879N 523864.0 5946733.2 13
SSA-ASP-SE501 D9G4A 105.46929W 53.74019N 469047.1 5954718.4 13
SSA-MIX-SE501 D9I1M 105.20643W 53.72540N 486379.7 5952989.7 13
SSA-MIX-SE501 F1N0M 104.53300W 53.80594N 530753.7 5962031.8 13
SSA-MIX-SE501 G4I3M 105.14246W 53.93750N 490677.3 5976354.9 13
SSA-CLR-SE501 FRSHCL 104.69194W 53.91639N 520205.2 5974269.4 13
--------------------------------------------------------------------------
Northern Study Area:
NSA-9BS-SE501 S8W0S 97.84024W 55.76824N 572761.9 6180894.9 14
NSA-9BS-SE501 T0P7S 98.82345W 55.88371N 511043.9 6193151.1 14
NSA-9BS-SE501 T0P8S 98.80225W 55.88351N 512370.1 6193132.0 14
NSA-9BS-SE501 T0W1S 97.80937W 55.78239N 574671.7 6182502.0 14
NSA-9BS-SE501 T3U9S 97.98339W 55.83083N 563679.1 6187719.2 14
NSA-9BS-SE501 T4U8S 97.99325W 55.83913N 563048.2 6188633.4 14
NSA-9BS-SE501 T4U9S 97.98364W 55.83455N 563657.5 6188132.8 14
NSA-9BS-SE501 T5Q7S 98.64022W 55.91610N 522487.2 6196800.5 14
NSA-9BS-SE501 T6R5S 98.51865W 55.90802N 530092.0 6195947.0 14
NSA-9BS-SE501 T6T6S 98.18658W 55.87968N 550887.9 6192987.9 14
NSA-9BS-SE501 T7R9S 98.44877W 55.91506N 534454.5 6196763.6 14
NSA-9BS-SE501 T7T3S 98.22621W 55.89358N 548391.8 6194505.6 14
NSA-9BS-SE501 T8S4S 98.37111W 55.91689N 539306.4 6197008.6 14
NSA-9BS-SE501 U5W5S 97.70986W 55.90610N 580655.5 6196380.8 14
NSA-9BS-SE501 U6W5S 97.70281W 55.91021N 581087.8 6196846.5 14
NSA-9JP-SE501 99O9P 99.03952W 55.88173N 497527.8 6192917.5 14
NSA-9JP-SE501 Q3V3P 98.02473W 55.55712N 561517.9 6157222.2 14
NSA-9JP-SE501 T7S9P 98.30037W 55.89486N 543752.4 6194599.1 14
NSA-9JP-SE501 T8Q9P 98.61050W 55.93219N 524334.5 6198601.4 14
NSA-9JP-SE501 T8S9P 98.28385W 55.90456N 544774.3 6195688.9 14
NSA-9JP-SE501 T8T1P 98.26269W 55.90539N 546096.3 6195795.3 14
NSA-9JP-SE501 T9Q8P 98.59568W 55.93737N 525257.1 6199183.2 14
NSA-9OA-SE501 T2Q6A 98.67479W 55.88691N 520342.0 6193540.7 14
NSA-ASP-SE501 P7V1A 98.07478W 55.50253N 558442.1 6151103.7 14
NSA-ASP-SE501 Q3V2A 98.02635W 55.56227N 561407.9 6157793.5 14
NSA-ASP-SE501 R8V8A 97.89260W 55.67779N 569638.4 6170774.8 14
NSA-ASP-SE501 S9P3A 98.87621W 55.88576N 507743.3 6193371.6 14
NSA-ASP-SE501 T4U5A 98.04329W 55.84757N 559901.6 6189528.2 14
NSA-ASP-SE501 T8S4A 98.37041W 55.91856N 539348.3 6197194.6 14
NSA-ASP-SE501 V5X7A 97.48565W 55.97396N 594506.1 6204216.6 14
NSA-ASP-SE501 W0Y5A 97.33550W 56.00339N 603796.6 6207706.6 14
NSA-MIX-SE501 Q1V2M 98.03769W 55.54568N 560718.3 6155937.3 14
NSA-MIX-SE501 T0P5M 98.85662W 55.88911N 508967.7 6193747.3 14
NSA-BRS-SE501 BRSOL 98.28889W 55.90528N 544441.4 6195777.7 14
NSA-TMK-SE501 TAMRK 98.42111W 55.91583N 536165.1 6196874.8 14
NSA-BRN-SE501 BRNJP 99.04383W 55.88184N 497240.1 6192940.9 14
--------------------------------------------------------------------------
7.1.2 Spatial Coverage Map
Not available.
7.1.3 Spatial Resolution
The 15-degree FOV of the SE-590 yielded a ground resolution of 79 m from the 300
m altitude.
7.1.4 Projection
Not applicable.
7.1.5 Grid Description
Not applicable.
7.2 Temporal Characteristics
7.2.1 Temporal Coverage
Observations were made during all three BOREAS 1994 IFCs, which occurred during
the following periods:
IFC-1 24-May - 16-June
IFC-2 19-July - 10-August
IFC-3 30-August - 19-September
Measurements were made as conditions permitted during each IFC.
7.2.2 Temporal Coverage Map
Observations were made at several sites on the following dates:
-----------------------------
Date Study Area
-----------------------------
31-May-94 SSA
1-Jun-94 SSA
4-Jun-94 SSA
6-Jun-94 SSA
7-Jun-94 SSA
8-Jun-94 NSA
10-Jun-94 NSA
21-Jul-94 NSA
22-Jul-94 SSA
23-Jul-94 SSA
24-Jul-94 SSA
25-Jul-94 SSA
28-Jul-94 SSA
4-Aug-94 NSA
8-Aug-94 NSA
6-Sep-94 NSA
8-Sep-94 NSA
9-Sep-94 NSA
13-Sep-94 NSA
15-Sep-94 SSA
16-Sep-94 SSA
7.2.3 Temporal Resolution
Measurements were collected as conditions permitted during each IFC. In
general, the helicopter would hover 1-2 minutes for each observation (consisting
of an average number of 20-25 scans). Each site was visited as often as
possible during each IFC, with priority given to tower flux sites and category 1
auxiliary sites. Helicopter flight time was limited to approximately 2 hours by
fuel constraints. As many sites as possible were visited during each flight.
7.3 Data Characteristics
Data characteristics are defined in the companion data definition file
(rs3se590.def).
7.4 Sample Data Record
Sample data format shown in the companion data definition file (rs3se590.def).
8. Data Organization
8.1 Data Granularity
All of the Reflectance Measured from a Helicopter-Mounted SE-590 data are
contained in one dataset.
8.2 Data Format(s)
The data files contain a series of numerical and character fields of varying
length separated by commas. The character fields are enclosed within single
apostrophe marks. There are no spaces between the fields. Sample data records
are shown in the companion data definition file (rs3se590.def).
9. Data Manipulations
9.1 Formulae
9.1.1 Derivation Techniques and Algorithms
From Vermote et al. (1997):
"Two atmospheric processes modify the solar radiance reflected by a target when
viewed from space: absorption by the gases (when observation bands are
overlapping gaseous absorption bands) and scattering by the aerosols and the
molecules. If the gaseous absorption can be de-coupled from scattering as if
the absorbents were located above the scattering layers, as assumed in the 6S
code, the equation of transfer for a Lambertian homogeneous target of
reflectance P_SFC at sea level altitude viewed by a satellite sensor (under
zenith angle of view theta_v and azimuth angle of view phi_v) and illuminated by
sun (theta_s, phi_s) is...:
P_TOA(theta_s, theta_v, phi_s-phi_v) =
T_g(theta_s, theta_v) *
[P_R+A + T_dn(theta_s) * T_up(theta_v) * {P_SFC / (1 - S*P_SFC)}]. (1)
The various quantities are expressed in terms of equivalent reflectance P
defined as P = pi * L /mu_s* E_s where L is the measured radiance, E_s is the
solar flux at the top of the atmosphere, and mu_s = cos(theta_s) where theta_s
is the solar zenith angle."
In addition, note the following notation (Vermote et al, 1997):
T_g Gaseous transmission of water vapor, carbon dioxide, oxygen
and ozone.
P_TOA Reflectance at the top of the atmosphere.
P_R+A Intrinsic reflectance of the molecule + aerosol layer.
T_dn Total transmission of the atmosphere on the path between the
sun and the surface.
T_up Total transmission of the atmosphere on the path between the
surface and the sensor.
S Spherical albedo of the atmosphere.
9.2 Data Processing Sequence
9.2.1 Processing Steps
The SE-590 sensor voltages were processed to at-sensor radiances (W/m2 sr mm)
following procedures described in Markham et al. (1988). Calibration
coefficients were obtained before and after the deployment at NASA GSFC and
onsite during the deployment using a portable calibration apparatus. The
individual data scans were examined and those with obvious spurious values (i.e.
outliers in the distribution) were removed.
The mean helicopter SE-590 radiances and sunphotometer data collected by the
onboard sunphotometer were then input into Version 4.0 of the 6S software
(Vermote et al., 1997) to obtain at-surface reflectance factors corrected for
atmospheric effects. A surface-based network of sunphotometers supplemented the
helicopter-based measurements of atmospheric conditions when the latter were
not available.
9.2.2 Processing Changes
None.
9.3 Calculations
9.3.1 Special Corrections/Adjustments
None.
9.3.2 Calculated Variables
See Section 9.1.1.
9.4 Graphs and Plots
Not included here. See Loechel et al., 1996.
10. Errors
10.1 Sources of Error
Potential sources of error include radiometric calibration; spectral
calibration; physical (environmental and human) conditions (including helicopter
vibration, minor changes in helicopter altitude and inclination); atmospheric
conditions, including atmospheric parameters estimated from the surface
sunphotometer network; and the atmospheric correction algorithm (Vermote et al.,
1997). Confidence intervals for the visible/near-infrared at-sensor radiance
values presented in this data set are within 3%. The possibility of errors
being introduced into the data set increases with additional manipulations of
the data. For an in-depth discussion of error considerations, see Markham et
al. (1988).
10.2 Quality Assessment
Visual quality assessment was performed during data collection. See reference
list and helicopter logs.
10.2.1 Data Validation by Source
None given.
10.2.2 Confidence Level/Accuracy Judgment
A thorough quantitative error analysis of this kind of data set is given in
Markham et al. (1988).
10.2.3 Measurement Error for Parameters
Confidence intervals for the at-sensor radiance values presented in this data
set are within 3%.
10.2.4 Additional Quality Assessments
See helicopter logs. Also, see reference: Walthall et al., 1997.
10.2.5 Data Verification by Data Center
A visual examination of all of the helicopter-mounted SE-590 at-surface
reflectances reveal artifacts from the atmosphere in all of the spectra. This
is especially obvious in the oxygen and water absorption regions in the near-
infrared. That all the atmospheric effects have not been removed from the near-
infrared bands causes one to suspect the atmospheric corrections in the visible
bands as well.
While the atmospheric effects on at-surface reflectance at any given wavelength
may be small, these effects may cause significant problems in some types of
hyperspectral analyses. Some analysis techniques look at band-to-band
covariances or derivatives. The atmospheric effects are nonlinear with
wavelength, and thus, by not completely removing these effects, the data become
questionable for those types of analyses.
11. Notes
11.1 Limitations of the Data
See section 10.2.5.
11.2 Known Problems with the Data
Caution should be used when using a band reflectance in the near-infrared
calculated with a gaseous transmittance much under 0.9; i.e., use caution in the
oxygen band (~760 nm) and the water vapor absorption band (~820 nm) -- where
absorption effects can be under/overestimated, respectively. It is suggested
that a neighboring band not affected by gaseous absorption be used, which seems
to characterize surface absorption effects well through the near-infrared.
Data collected over sparse canopies and with extreme solar geometry (i.e., early
morning/late afternoon observations) will contain substantial amounts of shadow,
which may complicate the retrieval of surface vegetation parameters.
In addition, isolated atmospheric events (such as forest fires or scattered
cloudiness) reduce the certainty in the atmospheric correction. The use of
surface-measured atmospheric variables contributes to error in the data set in
those cases.
11.3 Usage Guidance
See Sections 10.2.5, 11.1, and 11.2.
11.4 Other Relevant Information
None given.
12. Application of the Data Set
Research questions that may be examined with this data include:
� Retrieval of leaf area index (LAI) from spectral vegetation index.
� Scaling of spectral response in boreal regions (in combination with other
BOREAS data sets).
13. Future Modifications and Plans
None.
14. Software
14.1 Software Description
The software used in the atmospheric correction of this data set was 6S, Version
3.2 (Vermote et al., 1997).
14.2 Software Access
This software is public domain and available via anonymous ftp at
kratmos.gsfc.nasa.gov.
15. Data Access
15.1 Contact Information
Ms. Beth Nelson
BOREAS Data Manager
NASA GSFC
Greenbelt, MD
(301) 286-4005
(301) 286-0239 (fax)
Elizabeth.Nelson@gsfc.nasa.gov
15.2 Data Center Identification
See Section 15.1.
15.3 Procedures for Obtaining Data
Users may place requests by telephone, electronic mail, or fax.
15.4 Data Center Status/Plans
The RSS-03 helicopter SE-590 data are available from the Earth Observing System
Data and Information System (EOSDIS), Oak Ridge National Laboratory (ORNL)
Distributed Active Archive Center (DAAC). The BOREAS contact at ORNL is:
ORNL DAAC User Services
Oak Ridge National Laboratory
Oak Ridge, TN
(423) 241-3952
ornldaac@ornl.gov
ornl@eos.nasa.gov
16. Output Products and Availability
16.1 Tape Products
None.
16.2 Film Products
None.
16.3 Other Products
The data are available as American Standard Code for Information Interchange
(ASCII) files of helicopter SE-590 data.
17. References
17.1 Platform/Sensor/Instrument/Data Processing Documentation
Markham, B.L., D.L. Williams, J.R. Schafer, F. Wood, and M.S. Kim. 1995.
Radiometric characterization of diode-array field spectroradiometers. Remote
Sensing of Environment, vol. 51, pp. 317-330.
17.2 Journal Articles and Study Reports
Loechel, S., C.L. Walthall, E. Brown de Colstoun, J. Chen, and B. Markham.
1996. Spatial and temporal variability of surface cover at BOREAS using
reflectance from a helicopter platform. International Geosciences and Remote
Sensing Symposium (IGARSS), Lincoln, NE.
Markham, B.L., F.M. Wood Jr., and S.P. Ahmad. 1988. Radiometric calibration of
thereflective bands of NS001-thematic mapper simulator (TMS) and modular
multispectral radiometers (MMR). In Recent Advances in Sensors Radiometry and
Data Processing for Remote Sensing Proc. SPIE 24, pp. 96-108.
Sellers, P. and F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment
Plan. Version 1994-3.0 NASA BOREAS Report (EXPLAN 94).
Sellers, P. and F. Hall. 1996. Boreal Ecosystem-Atmosphere Study: Experiment
Plan. Version 1996-2.0 NASA BOREAS Report (EXPLAN 96).
Sellers, P. and F. Hall. 1997. BOREAS Overview Paper. JGR BOREAS Special Issue,
201.
Sellers, P., F. Hall, and K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere
Study: 1994 Operations. NASA BOREAS Report (OPS DOC 94).
Sellers, P., F. Hall, and K.F. Huemmrich. 1997. Boreal Ecosystem-Atmosphere
Study: 1996 Operations. NASA BOREAS Report (OPS DOC 96).
Sellers, P., F. Hall, H. Margolis, B. Kelly, D. Baldocchi, G. den Hartog, J.
Cihlar, M.G. Ryan, B. Goodison, P. Cril,l K.J. Ranson, D. Lettenmaier, and D.E.
Wickland. 1995. The boreal ecosystem-atmosphere study (BOREAS): an overview and
early results from the 1994 field year. Bulletin of the American Meteorological
Society. 76(9):1549-1577.
Strebel, D.E., D.R. Landis, K.F. Huemmrich, and W.W. Meeson. 1994. Collected
Data of The First ISLSCP Field Experiment, Volume 1: Surface Observations and
Non-Image Data Sets. Published on CD-ROM by NASA.
Vermote, E., D. Tanre, and J. Morcrette. 1997. Second simulation of the
satellitesignal in the solar spectrum, 6S: an overview. IEEE Trans. Geosci.
Remote Sens., vol. 35, no. 3, pp. 675.
Vermote, E., D. Tanre, J.L. Deuze, M. Herman, and J.J. Morcrette. 1996. Second
simulation of the satellite signal in the solar spectrum (6S), 6S User Guide
Version 1, October 7, 1996. University of Maryland/Laboratoire d'Optique
Atmospherique, 216 pp. (available via anonymous ftp at kratmos.gsfc.nasa.gov).
Walter-Shea, Elizabeth A. and Larry L. Biehl, 1990 "Measuring Vegetation
Spectral Properties", Remote Sensing Reviews Chapter 11, Edited by Narendra Goel
and John Norman, Vol. 5, pp 179-205.
Walthall, C., and E. Middleton. 1992. Assessing spatial and seasonal variations
in grasslands with spectral reflectances from a helicopter platform. J.
Geophys. Res., vol. 97, no. D17, pp. 18905-18912.
Walthall, C., D.L. Williams, B. Markham, J. Kalshoven, and R. Nelson. 1996.
Development and present configuration of the NASA GSFC/WFF helicopter-based
remote sensing system. International Geosciences and Remote Sensing Symposium
(IGARSS). Lincoln, NE.
17.3 Archive/DBMS Usage Documentation
None.
18. Glossary of Terms
None.
19. List of Acronyms
6S - Second Simulation of the Satellite Signal in the Solar Spectrum
AGL - Above Ground Level
ASCII - American Standard Code for Information Interchange
BOREAS - BOReal Ecosystem-Atmosphere Study
BORIS - BOREAS Information System
BSQ - Band Sequential
CCD - Charge-Coupled Device (??)
DAAC - Distributed Active Archive Center
DN - Digital Number
EOS - Earth Observing System
EOSDIS - EOS Data and Information System
FOV - Field of View
GSFC - Goddard Space Flight Center
IFC - Intensive Field Campaign
IFOV - Instantaneous Field of View
LAI - Leaf Area Index
MMR - Modular Multiband Radiometer
NASA - National Aeronautics and Space Administration
NSA - Northern Study Area
ORNL - Oak Ridge National Laboratory
PANP - Prince Albert National Park
RSS - Remote Sensing Science
SE-590 - Spectron Engineering spectroradiometer
SSA - Southern Study Area
SWIR - Short-Wave Infrared
TM - Thematic Mapper
URL - Uniform Resource Locator
UTM - Universal Transverse Mercator
VIS/NIR - Visible/Near-Infrared
WFF - Wallops Flight Facility
20. Document Information
20.1 Document Revision Date
Written: 31-Oct-1995
Last Updated: 02-Jul-1998
20.2 Document Review Date(s)
BORIS Review: 30-Nov-1997
Science Review:
20.3 Document ID
20.4 Citation
If this data set is referenced by another investigator, please acknowledge the
RSS03 investigation team and this document.
20.5 Document Curator
20.6 Document URL
KEYWORDS:
reflectance
radiometer
atmospheric correction
helicopter
RSS03_Helo_SE590.doc
07/07/98