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International cooperation and technology transfer
Mussio, Luigi

Figure 2: GCP identification - Homologous points on the orthophoto (left) and the amplitude image (right).
Figure 3: GCP identification - Homologous points on the orthophoto (left) and the coherence image (right).
The identification of natural GCPs on amplitude SAR
images is very demanding because such images are
considerably more difficult to interpret than optical images.
Their resolution in azimuth is greater than in slant range.
The images are highly distorted in the slant range
direction (e.g. foreshortening, layover) and that makes the
GCP recognition very difficult. Furthermore, speckle
handicaps the image interpretation very much. To bypass
this last problem, the images are usually azimuth-
compressed. The compression reduces the noise and
improves the image interpretation.
In many cases it is difficult to measure a sufficient set of
3D GCPs. On the other hand, it is easier to recover height
GCPs, i.e. points whose height is known accurately but
which are not very well defined in planimetry (e.g. points
chosen in the centre of flat fields or flat homogeneous
areas). Our calibration accepts either full or height GCPs:
the height GCPs are introduced in the same way as the
full ones. However, their contribution to the LS adjustment
is differentiated through the stochastic model, i.e. they are
distinguished from the full GCPs through their variance-
covariance matrix.
In the last three years we were involved in a EU
Concerted-Action called ORFEAS (Optical-Radar sensor
Fusion for Environmental Applications), joining five
European research groups (University of Thessaloniki.
Cartographic Institute of Catalonia. ETH Zurich, Technical
University of Graz and Polytechnic of Milan). A
comprehensive data set. covering South Catalonia - Spain