Example of processing of the RADARSAT-1
SAR stereo pair for "Trieste" site.
As an example of processing of the RADARSAT-1 SAR stereo
data the pair of images acquired over south Europian region
was selected. It is an area of intersection of the three state
borders: Austrian, Slovenian, and Italien. The Alps occupy
the most part of scenes. In lower part of map — a part of Venetian
bay, Adriatic sea.
The input scenes have been presented in SGF (SAR georeferenced)
format. These are images in the ground path projection and
with axes "radar slow time — ground range". The
scenes were acquired in standard stripmap mode by S3 and S7
beams. The viewing geometry is shown on the figure below:
These images cover a surface area more than 10000 sq. km.
Imaged terrain is mostly mountained and contains elevations
up to 3000 m. Incidence angles on the scene center for
the beams S3 and S7 are 34 and 47 degrees, so the difference
of 12 degrees for the mountained relief provides the clear
distinguished parallaxes. As the master image the scene S3
was selected. The images of processed stereo pair are shown
on the picture below:
On the first stage, according to adopted methodology
of processing, the co-registration of stereo images was performed.
The goal of this operation is a spatial overlapping of images
and the interesting subset selection.
The co-registration has been performed with
use of ground tie points, which were set on the input images.
Tie points have been selected over simple identified objects
on the both images. The process was interactive and included
the control of RMS errors, introduced by each tie point.
On the second stage — automatic digital matching
— the processing was performing with use of approach exploited
adaptive correlation window. The window sizes on the each
matching level and for each image point were selecting automatically.
Other processing parameters (number of matching levels, search
range boundaries, and compression factor for each particular
level) were selecting by operator. They are shown below:
The step by step dynamic of output file generation
during hierarchical matching is shown on the picture below:
The result of digital matching — parallaxes matrix expressed
in gray levels and pseudo color presentation looks like following:
On the next stage the parallaxes file was geocoded (orthorectified),
i.e. transformed with account of its own elevations into a
normal projection on the geographic grid above the reference
ellipsoid WGS84. Created raster presents the digital elevation
The perspective presentation of created elevations
matrix and anaglyph picture of its part are shown below: