L. Prevot et al., ESTIMATING THE CHARACTERISTICS OF VEGETATION CANOPIES WITH AIRBORNE RADAR MEASUREMENTS, International journal of remote sensing, 14(15), 1993, pp. 2803-2818
Possible use of synthetic aperture radars (SAR) for monitoring agricul
tural canopies is investigated in this paper. Data have been acquired
on the Orgeval watershed during the AGRISCATT'88 campaign. Four radar
experiments were carried out with the airborne scatterometer ERASME (C
and X bands, HH and VV polarizations, multi-incidence angles). Simult
aneous ground measurements (soil moisture, leaf area index, water cont
ent of the canopy,...) were conducted on 11 wheat fields. Backscatteri
ng coefficients of the canopies are interpreted in the framework of se
mi-empirical 'water-cloud' models. A simple parametrization of the ang
ular effect of soil roughness is introduced, allowing the simultaneous
use of multi-incidence angle radar data. With a unique set of paramet
ers for each radar configuration (frequency and polarization) the wate
rcloud model appears to describe adequately the backscattering of all
the fields, over the range of incidence angles. It is shown that in th
is case, attenuation is the dominant effect of the vegetation and an i
nversion algorithm is proposed for estimating the water content of veg
etation. This algorithm requires measurements at two different inciden
ce angles and various combinations of radar configurations are then te
sted.