Synthetic aperture radar interferometry(6)
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.13.Block diagram showing the major steps in interferometric processing to generate topographic maps.Data for each interferometric channel are processed to full resolution images using the platform motion information to compensate the data for perturbations from a straight line path.One of the complex images is resampled to overlay the other,and an interferogram is formed by cross-multiplying images,one of which is conjugated.The resulting interferogram is averaged to reduce noise.Then,the principal value of the phase for each complex sample is computed.To generate a continuous height map,the two-dimensional phase field must be unwrapped.After the unwrapping process,an absolute phase constant is determined.Subsequently,the three-dimensional target location is performed with corrections applied to account for tropospheric effects.A relief map is generated in a natural coordinate system aligned with the flight path.Gridded products may include the target heights,the SAR image,a correlation map,and a height error
map.
Fig.14.Sensitivity tree showing the sensitivity of target location
to various parameters used in interferometric height reconstruction.
See Fig.15for definitions of angles.orthogonal to the velocity vector,the velocity errors do not
contribute to target position errors.Fig.14graphically de-
picts the sensitivity dependencies,according to the geometry
defined in Fig.15.
To highlight the essential features of the interferometric
sensitivity,we simplify the geometry to a flat earth,with
the Fig.15.Baseline and look angle geometry as used in sensitivity
formulas.
baseline in a plane perpendicular to the velocity vector.With this geometry the baseline and velocity vectors are given
by
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
and
is baseline
length,
is the look angle,as shown in Fig.9.These formulas are
useful for assessing system performance or making trade
studies.The full vector equation however is needed for use
in system calibration.
The sensitivity of the target position to platform position
in the along-track
direction,and
vertical
direction
have larger cross track position errors
than vertical errors.
The sensitivity of the target position to errors in the base-
line length,and baseline roll angles are given
by
is1or2for single transmit or ping-pong modes.This
is inversely proportional to the perpendicular component of
the
baseline,
is obtained from the third component of(30).
Fig.16represents an example of an interferometric
SAR system for topographic mapping.Several parameters
defining the performance sensitivity,and therefore calibra-
tion of the interferometer,relate directly to radar hardware
observables.
•Baseline vector,including length and attitude,for
reduction of interferometric phase to height.This pa-
rameter translates to knowing the locations of the phase
centers of the interferometer antennas.
•Total radar range,
say
and
,between channels,for determi-
nation of the topography.This parameter translates to
knowing the phase delays through the receiver
chains,
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