1040
stage of growth the assumption of vegetation homo
geneity does not apply any longer and the model must
be extended to a two-layer model with separate values
for C and D, (Hoekman e.a. 1982)
Recently it was suggested to improve the cloud mo
del further by the introduction of polarization de
pendence (Allen e.a. 1984).
REFERENCES
Allen, C.T. & F.T.Ulaby 1984. Modelling the polari
zation dependence of the attenuation in vegetation
canopies. Proc. IGARSS, Vol 1, pi 19-124.
Attema, E.P.W. &F.T.Ulaby 1978. Vegetation modelled
as a water cloud. Radio Science, Vol 13, No 2,
P357-364.
Attema, E.P.W. & P.J. Kats, van & L.Krul 1982. A
radar signature model for partially coherent scat
tering from irregular surfaces. IEEE Trans. Geo
science and Remote Sensing GE 20 nr. 1 p76-84.
Attema, E.P.W. & P.Snoeij 1984. Dutscat, a 6-freq
uency airborne scatterometer. Proc. Earsel work
shop. ESA-sp 227, pl27-129, Amsterdam.
Hoekman, D.H. & E.P.W.Attema & L.Krul 1982. A multi
layer model for radar backscattering by vegetation
canopies. Proc. IGARSS, Vol II pTA-1, 4.1.4.7.
Hoogeboom, P. 1983. Classification of agricultural
crops in radar images. IEEE Trans. Geoscience and
Remote Sensing, vol GE21, nr. 3, p329-336.
Krul, L. 1979. The modelling Problem an introduction.
Proc. Earsel-workshop: Microwave Remote Sensing on
Bare Soil, p85-95.
Krul, L. 1981. Scatterometer Systems. Proc. ESA-
Earsel workshop, ESA SP-166, pl9-27, Alpbach.
Loor, G.P. de 1974. Measurements of radar ground
returns. Proc. URSI Specialist Meeting Microwave
Scattering and Emission from the Earth, pl85-195,
Berne.
Megier, J. & W.Mehl & R.Ruppelt 1985. Methodological
studies of rural land use classification of SAR and
multi-sensor imagery. Investigators Final Report
SAR-580, p693-721.
Ruck, G.T. et al 1970. Radar Cross Section Handbook.
Plenum Press, London.
Smit, M.K. 1979. Preliminary results of an investi-
gatioh into the potential of applying X-band SLR-
images for crop type inventory purposes. IEEE Trans.
Geosc. Electr. 17, p303-308.
