Corn growth as monitored by radar

Abstract

Results of an experiment to determine the feasibility of monitoring corn growth with radar are reported. Radar backscattering data were acquired with a ground based 8-18 GHz radar spectrometer during the summer of 1974. Supporting ground truth data were also collected. During the month of July the crop suffered from a water deficit, although by no means was the crop destroyed by this lack of moisture. At angles of incidence of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">40\deg</tex> or greater, the results of the data analysis indicate a strong correlation between the radar backscattering coefficient <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\sigma\deg</tex> and the "normalized plant water content" <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">W_{pn}</tex> , where <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">W_{pn}</tex> is the mass of water in the corn plant divided by its height. The correlation coefficient between <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\sigma\deg</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">W_{pn}</tex> , which was calculated for each of 176 different combinations of the radar parameters (signal frequency, angle of incidence and polarization), was highest (0.96) at 17.0 GHz, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50\deg</tex> VV polarization. Considering the fact that the data used covered a period of four months during which the corn plants underwent considerable change in geometry and dielectric properties, the high correlation of 0.96 between <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\sigma\deg</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">W_{pn}</tex> points to a promising future for radar as a tool for monitoring corn development.