is used by us to generate initial approximate
orientation parameters along orbital paths. We
conclude that fewer than 10 ground control points
are quite enough for space resection (Chen and
Lee,1990). It is interesting to note that the re-
section procedure is equally applicable to a sin-
gle SPOT scene or to multiple scenes in stere-
oscopy. As far as improvements on additional
self-calibrating parameters are concerned more
research on our part is necessary.
One of the purposes in studying our integrated
model for image matching and 3D positioning
is to test its applicability to spaceborne stereo
imagery. We know there is an advantage in theo-
retical analysis on error propagation; it is a wor-
thy trade-off when thinking about rather heavy
computational loads. Another advantage inher-
ent in the integrated approach is automatic gen-
eration of orthographic (sub-)images along with
that of a dense digital elevation model. Cur-
rently, we must impose weights in form of a di-
agonal matrix on unknown height parameters of
DEMs. This arises in part from the fact there
exists locally no or little image contrast in SPOT
sub-images. Therefore, our on-going research ef-
forts are led to
- determine in image preprocessing weighting
functions that allow for gray-value contrast,
textures or features in (sub-)images;
- design regional radiometric parameters to re-
place two global parameters ro, r1 in Eq.(3b);
- discover methods of interpolation more realis-
tic than those by non-differentiable, contin-
uous piecewise linear or patchwise bilinear
modeling;
- as a long-term goal correct radiometrically for
atmospheric effects and terrain effects to ar-
rive at normalized reflectance images for pho-
togrammetric multi-point positioning.
At last, we kindly acknowledge the research funds
provided by the Sinotech Foundation for Re-
search and Development of Engineering Sciences
and Technologies.
650
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