The purpose of this experiment is to characterize a spring wheat canopy by its reflectance at various view and illumination angles and by its physical and agronomic attributes. Reflectance measurements were acquired from 0.46 to 2.40 um using an Exotech model 20C spectroradiometer. at view zenith angles of 0, 15, 30, 45 and 60 degrees and view azimuth angles of 0, 45, 90, 135, 180, 225, 270, and 315 degrees. Spectral data and a photograph of the instrument field of view were taken in each of the 33 view directions. The field of view of the Exotech 20C was 15 degrees and the vertical height of the system above the soil was 7.6 meters. These data were collected for various solar zenith and azimuth angles during five days each representing a different development stage for the spring wheat canopy. Measurements were also made of leaf transmittance. An ancillary data set was collected in conjunction with reflectance measurements to describe the spring wheat field by its canopy geometry, ground cover, biomass, leaf area index and development stage.
On two of the four days, June 19 and July 17, polarization measurements were collected. The polarization data for these days only include wavelengths from 0.46-0.72 um since the polarizing material that was used was only good for the visible wavelengths. A polarization analyzer, a sheet of polarizing film mounted in a rotateable bracket, was attached to the spectroradiometer at the entrance port. In each view direction, two spectra were acquired, one with the polarization analyzer oriented for maximum detector signal amplitude and the other with the analyzer oriented for minimum signal. See reference for details of an analysis of this polarization data.
The test took place in 1976.
The supporting docs include a brief summary of used instruments, a wavelength table (Wavelength_ASCII.txt), reflectance note and reflectance tables (ReflectanceTable206.txt and ReflectanceTableMulti.txt), and file format description (ExperimentDataFormat3.txt). The format description file is in ASCII format in lines of 80 characters.
This research dataset is part the Field Research Data Library that consists of over 200,000 spectral observations of soils and vegetation that have been collected since 1972 till 1991 as part of the research focused on vegetation and soils at the Laboratory for Applications of Remote Sensing (LARS) located at the Purdue University.
Cite this work
Researchers should cite this work as follows:
- Location: Experiment Station, Williston, ND
- County: Williams
- Latitude/Longitude: 0480800N 1034400W
- Illumination: Solar
- Spectrometer: Exotech 20C-SW
- Wavelength Range: 0.40-2.40 um
- Experiment Type: Crops - Spring Wheat