DOI: 10.4231/r73f4mj6
title: Tower Sunflower Polarization (916403)

description: &lt;p&gt;This experiment includes sunflower polarization data collected from a 13.5 meter tower over a 100 meter by 100 meter plot at the Montfavet INRA facility.&lt;/p&gt;

&lt;p&gt;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.&lt;/p&gt;

&lt;p&gt;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.&lt;/p&gt;

&lt;p&gt;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).&lt;/p&gt;

&lt;p&gt;Other measurements collected in conjunction with the reflectance measurements included leaf reflectance and transmittance, biomass, leaf area index, development stage.&lt;/p&gt;

&lt;p&gt;The experiment is described in more detail in an IGARSS 92 paper entitled &quot;Directional and Temporal Variability of the APAR/VI Relationships. The Case of a Sunflower Canopy&quot; by F. Baret et. al.&lt;/p&gt;

&lt;p&gt;Descriptions of Some of the Units Used in the Data Files.&lt;/p&gt;

&lt;dl&gt;
 &lt;dt style="font-weight:normal"&gt;1. Irradiance Azimuth Angle&lt;/dt&gt;
 &lt;dd&gt;This angle represents the direction of the solar disc measured clockwise from North. In other words it is the azimuthal angle from which the directional solar rays are coming.&lt;/dd&gt;
 &lt;dt style="font-weight:normal"&gt;2. Irradiance Zenith Angle&lt;/dt&gt;
 &lt;dd&gt;This angle represents the direction of the solar disc measured from a vertical line passing through the earth at the sunflower field.&lt;/dd&gt;
 &lt;dt style="font-weight:normal"&gt;3. View Azimuth Angle&lt;/dt&gt;
 &lt;dd&gt;This angle represents the direction that the multiband radiometers are viewing towards measured clockwise from North.&lt;/dd&gt;
 &lt;dt style="font-weight:normal"&gt;4. View Zenith Angle&lt;/dt&gt;
 &lt;dd&gt;This angle represents the direction that the multiband radiometers are viewing measured from a vertical line passing through the earth at the sorghum field.&lt;/dd&gt;
 &lt;dt style="font-weight:normal"&gt;5. Experimenter Parameter 1 (from Parameter Description File)&lt;/dt&gt;
 &lt;dd&gt;Raw data for the Barnes (serial number 104) detector temperature.&lt;/dd&gt;
 &lt;dt style="font-weight:normal"&gt;6. Experimenter Parameter 2 (from Parameter Description File)&lt;/dt&gt;
 &lt;dd&gt;Raw data for the Barnes (serial number 105) detector temperature.&lt;/dd&gt;
 &lt;dt style="font-weight:normal"&gt;7. Experimenter Parameter 3 (from Parameter Description File)&lt;/dt&gt;
 &lt;dd&gt;Raw data for the Barnes (serial number 108) detector temperature.&lt;/dd&gt;
 &lt;dt style="font-weight:normal"&gt;8. Experimenter Parameter 4 (from Parameter Description File)&lt;/dt&gt;
 &lt;dd&gt;The &#39;New Code&#39; assigned to a series of measurements.&lt;/dd&gt;
 &lt;dt style="font-weight:normal"&gt;9. Experimenter Parameter 5 (from Parameter Description File)&lt;/dt&gt;
 &lt;dd&gt;The voltage measurement from the yellow inclinometer. This inclinometer is used for view zenith angles from 0 to 70 degrees.&lt;/dd&gt;
 &lt;dt style="font-weight:normal"&gt;10. Experimenter Parameter 6 (from Parameter Description File)&lt;/dt&gt;
 &lt;dd&gt;The voltage measurement from the red inclinometer. This inclinometer is used for view zenith angles from -70 to 0 degrees.&lt;/dd&gt;
 &lt;dt style="font-weight:normal"&gt;11. Experimenter Parameter 7 (from Parameter Description File)&lt;/dt&gt;
 &lt;dd&gt;The voltage measurement for the azimuth/calibration encoder channel.&lt;/dd&gt;
 &lt;dt style="font-weight:normal"&gt;12. Experimenter Parameter 8 (from Parameter Description File)&lt;/dt&gt;
 &lt;dd&gt;The voltage measurement for Licor Monitor channel.&lt;/dd&gt;
 &lt;dt style="font-weight:normal"&gt;13. Experimenter Parameter 9 (from Parameter Description File)&lt;/dt&gt;
 &lt;dd&gt;The view zenith angle in degrees to one decimal place. (The view zenith angle given in &#39;T02&#39; line of the data base is to the nearest integer value.&lt;/dd&gt;
&lt;/dl&gt;

&lt;p&gt;Revised (9-22-93)&lt;/p&gt;
description: The purpose of this experiment was to characterize the polarization of a 100 meter by 100 meter sunflower plot at the Montfavet INRA facility, France