The purpose of this experiment was to characterize the polarization of a 100 meter by 100 meter sunflower plot at the Montfavet INRA facility. The polarization data along with many other canopy measurements will serve as a basis for research involving the spectral, directional and polarization characteristics of reflected light. Data from three Barnes 12-1000 and four Cimel multiband radiometers were collected on 10 dates during July and early August. Reflectance polarization measurements were acquired in five Landsat Thematic Mapper wavelength bands (0.45-0.52 um, 0.52-0.60 um, 0.63-0.69 um, 0.76-0.90 um, 1.55-1.75 um) plus a 1.15-1.30 um band and 3 SPOT bands (0.50-0.59 um, 0.62-0.68 um, 0.79-0.89 um). Measurements were collected for view zenith angles at about every 2 degrees from 0 to 70 degrees and view azimuth angles of 0, 45, 90, 135, 180, 225, 270, 315 degrees and 0, 90, 180 and 270 degrees relative to the solar illumination azimuth angle. Polarization measurements were also made of the sky conditions for view zenith angles at about every 2 degrees from 180 (straight up) to 110 degrees and view azimuth angles of 90, 180, and 270 degrees relative to the solar azimuth.
The radiometers were mounted on a 13.5 meter tower in the middle of the sunflower canopy. A set of sunflower measurements consists of 2 reps of 12 azimuth angles. A set of sky data consists of 3 azimuth angles. No data were collected for the azimuth angle towards the sun so as not to risk damaging the detectors.
The field of view of the Barnes multiband radiometers was 1 degree; the field of view of one Cimel that had no polarizing filters was 12 degrees. The field of view of the three Cimel multiband radiometers that contained polarizing filters was 1 degree before 7/25 and 12 degrees on 7/25 and thereafter. The data were collected from a height of 13.5 meters above the canopy. There were three channels of data collected for each of the nine wavelength bands listed above each having a polarizing film oriented at a different angle The three relative polarizer angles were 0, 45 and 90 degrees. Data were also collected for 6 wavelength bands with no polarizing film (0.50-0.59 um, 0.62-0.68 um, 0.79-0.89 um and 3 of 2.08-2.35 um).
Other measurements collected in conjunction with the reflectance measurements included leaf reflectance and transmittance, biomass, leaf area index, development stage.
The experiment is described in more detail in an IGARSS 92 paper entitled "Directional and Temporal Variability of the APAR/VI Relationships. The Case of a Sunflower Canopy" by F. Baret et. al.
Descriptions of Some of the Units Used in the Data Files.
1. Irradiance Azimuth Angle
2. Irradiance Zenith Angle
3. View Azimuth Angle
4. View Zenith Angle
5. Experimenter Parameter 1 (from Parameter Description File)
6. Experimenter Parameter 2 (from Parameter Description File)
7. Experimenter Parameter 3 (from Parameter Description File)
8. Experimenter Parameter 4 (from Parameter Description File)
9. Experimenter Parameter 5 (from Parameter Description File)
10. Experimenter Parameter 6 (from Parameter Description File)
11. Experimenter Parameter 7 (from Parameter Description File)
12. Experimenter Parameter 8 (from Parameter Description File)
13. Experimenter Parameter 9 (from Parameter Description File)
A summary of the data sets follow.
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Set Time Range Illumination Angles Cloud Scene
zenith azimuth Cover
(GMT) (degrees) (%)
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7/10/91
Practice Data Set.
7/11/91 (4043 observations)
1 8:47- 9:11 42-38 106-112 ? Sunflowers
2 9:15- 9:18 38-37 113-114 ? Sky
3 9:47-10:14 33-29 122-132 ? Sunflowers
4 10:19-10:23 28-28 134-135 ? Sky
5 12:18-12:49 23-25 200-216 ? Sunflowers
6 13:04-13:08 27-28 223-225 ? Sky
7 14:42-14:14 42-48 254-261 ? Sunflowers
8 15:20-15:26 49-50 262-263 ? Sky
7/12/91 (2226 observations)
1 9:57-10:24 31-28 125-135 ? Sunflowers
2 10:34-10:38 6-26 140-142 ? Sky
3 13:28-13:59 35-35 242-242 ? Sunflowers
4 14:12-14:24 37-39 246-249 ? Sky
7/15/91 (999 observations)
1 14:51-15:19 44-49 255-261 ? Sunflowers
2 15:33-15:36 52-52 264-264 ? Sky
7/16/91 (5280 observations)
1 08:58-09:23 41-37 109-115 ? Sunflowers
2 09:42-09:44 34-34 121-122 ? Sky
3 11:26-11:52 23-22 168-184 ? Sunflowers
4 12:07-12:10 23-23 193-194 ? Sky
5 12:26-12:52 24-26 204-217 ? Sunflowers
6 13:06-13:10 28-28 223-225 ? Sky
7 13:47-14:10 34-37 238-245 ? Sunflowers
8 14:26-14:28 40-40 249-249 ? Sky
9 14:54-15:20 45-49 256-261 ? Sunflowers
10 15:36-15:40 52-53 264-265 ? Sky
7/25/91 (3750 observations)
1 07:56-08:34 53-47 98-105 ? Sunflowers
2 08:52-08:58 44-42 109-111 ? Sky
3 09:15-09:51 40-34 115-126 ? Sunflowers
4 10:04-10:07 32-32 130-131 ? Sky
7/26/91 (857 observations)
1 07:45-08:01 55-53 96- 99 ? Sunflowers
7/27/91 (9664 observations)
1 08:05-08:42 52-45 100-108 ? Sunflowers
2 08:51-08:54 44-44 110-110 ? Sky
3 09:10-09:40 41-36 114-123 ? Sunflowers
4 09:52-09:55 34-34 127-128 ? Sky
5 10:11-10:45 32-28 133-147 ? Sunflowers
6 10:58-11:00 27-26 154-154 ? Sky
7 11:19-11:58 25-25 164-186 ? Sunflowers
8 12:17-12:20 25-25 197-198 ? Sky
9 14:09-14:41 39-44 242-250 ? Sunflowers
10 14:59-15:01 47-47 254-255 ? Sky
7/29/91 (610 observations)
1 15:27-15:39 52-54 260-262 ? Sunflowers
8/2/91 (9891 observations)
1 08:56-09:29 44-39 112-121 ? Sunflowers
2 09:48-09:51 36-36 127-128 ? Sky
3 12:09-12:47 26-29 192-211 ? Sunflowers
4 12:55-12:57 30-30 214-215 ? Sky
5 13:13-13:50 32-37 222-235 ? Sunflowers
6 14:03-14:05 39-39 239-239 ? Sky
7 14:22-14:56 42-47 244-252 ? Sunflowers
8 15:08-15:10 49-50 255-255 ? Sky
9 15:53-16:44 57-67 264-267 ? Sunflowers
10 17:05-17:09 70-71 276-277 ? Sky
8/5/91 (9813 observations)
1 08:07-08:47 53-46 102-111 ? Sunflowers
2 09:18-09:20 41-41 119-119 ? Sky
3 09:36-10:13 38-33 124-137 ? Sunflowers
4 10:25-10:27 32-32 141-142 ? Sky
5 10:50-11:24 29-27 152-168 ? Sunflowers
6 11:40-11:42 27-27 177-178 ? Sky
7 12:02-12:37 27-29 189-206 ? Sunflowers
8 12:52-12:54 30-30 213-213 ? Sky
9 14:23-15:00 42-49 244-253 ? Sunflowers
10 15:13-15:15 51-51 255-256 ? Sky