Synthetic aperture radar interferometry(11)
时间:2025-07-11
时间:2025-07-11
Synthetic aperture radar interferometry is an imaging technique for measuring the topography of a surface, its changes over time, and other changes in the detailed characteristics of the surface. By exploiting the phase of the coherent radar signal, interf
Fig.21.Baseline decorrelation for various point target response functions.The solid line is for standard sinc response with no weighting.The dashed,dotted–dashed,dotted,and triangled lines are weightings of half-cosine,Hanning,Hamming,and optimized cosine,respectively.
It was shown in[23]
that
(63)
provided the scattering volume could be regarded as homo-
geneous in the range direction over a distance defined by the
range resolution.The
function
is the effective normalized backscatter cross sec-
tion per unit height.The term“effective”is used to indicate
that is the intrinsic cross section of the medium atten-
uated by all propagation losses through the medium.The
specific form
for depends on the scattering medium.
Models for this term,and its use in the remote sensing of
vegetation height,will be discussed in the applications sec-
tion of this paper.
In repeat-pass systems,there is another source of decor-
relation.Temporal
decorrelation
(shaded boxes)
as scattering from the volume contributes within a resolution
cell.
,the correlation due to thermal noise alone,can be written
as
(65)
where channel.In addi-
tion to thermal noise,which is additive,SAR returns also
have other noise components,due to,for example,range
and Doppler ambiguities.An expression for the decorrela-
tion due to this source of error can only be obtained for ho-
mogeneous scenes,since,in general,the noise contribution
is scene dependent.Typically for simplicity these ambigui-
ties are treated as additive noise as part of the overall system
noise floor.
In general,the full correlation will comprise contribution
from all these
effects
Synthetic aperture radar interferometry is an imaging technique for measuring the topography of a surface, its changes over time, and other changes in the detailed characteristics of the surface. By exploiting the phase of the coherent radar signal, interf
Fig.23.(a)Correlation image in radar coordinates of Algodones Dunefield,CA,measuring the sameness of the two images acquired one day apart used to form an ERS-1/2radar interferogram.Blue denotes low correlation,purple moderate correlation,and yellow-green high correlation.Salton Sea decorrelates because water changes from one second to the next.Some agricultural fields and dune areas decorrelate from over the one day period.Mountains decorrelate from baseline decorrelation effects on high slopes rather than temporal effects.Dunes remain well correlated in general over one day.(b)Five month correlation map showing large decorrelation in the unvegetated Algodones dunes but significantly less in much of the vegetated area to the west(in box).(c)Ground photo of vegetated dune area in box.
Rodríguez and Martin[23]presented the analytic expression
for the Cramer–Rao bound[54]on the phase variance
(67)
The variable
200m/s)and
spaceborne platforms(
Synthetic aperture radar interferometry is an imaging technique for measuring the topography of a surface, its changes over time, and other changes in the detailed characteristics of the surface. By exploiting the phase of the coherent radar signal, interf
platforms are limited in their ability to repeat their flight track
spatially with sufficient control.For a given image resolu-
tion and wavelength,the critical baseline for spaceborne plat-
forms is longer than airborne platforms by the ratio of their
target ranges,typically a factor in the range of20–100.For
example,a radar operating at C-band at40-MHz range band-
width looking at35
denote
the range-compressed presummed signal data for a pulse,
with.The motion
compensated signal is given by
(68)
where is
the range component of the displacement from the reference
path to the actual antenna location.This is denoted and
in Fig.24for the two interferometric antennas and is
given by
(69)
where
…… 此处隐藏:2057字,全部文档内容请下载后查看。喜欢就下载吧 ……