Characterization Soybean Field Sun-View Angle (801802)

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By K. Jon Ranson

Purdue University

The purpose of this experiment is to characterize a soybean field by its reflectance at various view and illumination angles and by its physical and agronomic attributes.

Additional materials available

Version 1.0 - published on 06 Apr 2015 doi:10.4231/R7TT4NWD - cite this Archived on 25 Oct 2016

Licensed under CC0 1.0 Universal

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Description

The purpose of this experiment is to characterize a soybean field by its reflectance at various view and illumination angles and by its physical and agronomic attributes. Reflectance measurements were acquired in the four Landsat wavelength bands through view zenith angles of 0, 7, 15, 22, 30, 45 and 60 degrees and view azimuth angles of 0, 45, 90, 135, 180, 225, 270, and 315 degrees. The field of view of the Landsat band radiometer was 10 degrees and the vertical height of the multiband radiometer above the ground was ten meters. These data were collected for various solar zenith and azimuth angles during three days each representing a different development stage for the soybean canopy. Measurements were also made of leaf transmittance.

An ancillary data set was collected in conjunction with reflectance measurements to describe the soybean field by its canopy geometry, ground cover, biomass, leaf area index and development stage. These data sets satisfy the input requirements for testing the validity of most mathematical models of canopy reflectance.

Photographs were also obtained to coincide with each spectral observation.

The development stages of the soybeans for the three dates spectral data were collected are recorded in the support file development_stages_801802.txt

Also canopy geometry measurements were collected for 25 cm. of row at 2 locations in each field for each date. The geometry measurements included:

  • XYZ location of each leaf
  • theta , phi orientation of each leaf
  • Area of each leaf

LARSPEC Identification Record Codes

1. Scene Type

The pair of numbers after 'SOYBEANS' or 'BARE SOIL' indicate the nominal view zenith and azimuth directions - zenith first, azimuth last. Nominal refers to the angles marked on the platform that were used for reference during data acquisition. The actual view zenith angle and azimuth angle are stored in the LARSPEC identification records under view zenith angle (VIZE) and view azimuth angle (VIAZ), respectively. The actual view zenith angle differs from the nominal view zenith angle for the first two days because the platform on which the Exotech 100 was rotated was not level. Therefore the view zenith angle changed for different view azimuth angles. On the third date of data collection a new mounting apparatus was used which made it possible to level the platform. Therefore the nominal view zenith angle and actual view zenith angle are the same for the third day.

2. Irradiance Azimuth Angle

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.

3. Irradiance Zenith Angle

This angle represents the direction of the solar disc measured from a vertical line passing through the earth at the soybean field.

4. View Azimuth Angle

This angle represents the direction that the Exotech 100 Landsat band radiometer is viewing towards measured clockwise from North.

5. View Zenith Angle

This angle represents the direction that the Exotech 100 Landsat band radiomenter is viewing measured from a vertical line passing through the earth at the soybean field.

 The test took place in 1980.

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.

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Notes

Location: Joe Kerkhove Farm, West Lafayette, IN
County: Tippecanoe
Latitude/Longitude: 0403030N 0870000W
Illumination: Solar
Experiment Type: Crops - Soybean, Soil
Radiometer: Exotech 100
Wavelength Range: 0.50-1.10 um

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