International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B2. Istanbul 2004
4.4 Image Matching and 3-D Reconstruction
Object space reconstruction is the prime objective of
photogrammetry. Traditionally, this process starts by matching
points in the image space. However, matching points encounter
many problems due to different geometric and radiometric
differences between the images as well as repeated signals. It is
very hard to reduce or eliminate mismatched automatically — it
is up to the human operator to reject them. Apart from points,
Habib and Kelley (2001) used the MIHT strategy to estimate the
Relative Orientation Parameters (ROP) between stereo-pair of
images using linear features. The suggested approach was
successful in dealing with large-scale imagery over urban areas,
which proved to be difficult when using traditional matching
procedures. Habib et al. (2003a) extended this approach to
allow for the reconstruction of corresponding 3-D linear
features, Figure 6. Such an approach can be expanded to allow
for surface reconstruction, ortho-photo generations, and object
recognition applications.
(c)
Figure 6: Left (a) and right (b) images containing matched
linear features and the reconstructed 3-D linear
feature (c)
4.5 Photogrammetric and Medical
Registration
Image-to-Image
With the enormous increase in earth observing satellites, there
has been an urgent need for establishing automatic and accurate
registration techniques of multi-source imagery with varying
geometric and radiometric properties. Traditional image
registration techniques require distinct points, which have to be
identified in the imagery. However, identifying conjugate points
in imagery with varying geometric and radiometric resolutions
is difficult. Habib and Al-Ruzouq (2004) used linear features for
the co-registration of scenes captured by space-borne linear
array scanners. The MIHT strategy has been implemented to
automatically establish the correspondence between conjugate
linear features as well as estimate the parameters relating the
involved scenes. Figure 7 shows straight-line fcatures digitized
in SPOT and IKONOS scenes as well as a mosaic scene
generated after establishing the registration.
(a) (b) (c)
Figure 7. SPOT (a) and IKONOS (b) scenes with digitized
linear features, which are used to generate a
composite mosaic (c)
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Similarly, in medical images, it is often hard to find conjugate
points, Figure 8. Linear features, as seen in the same figure, can
be used instead to facilitate the registration between the images,
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Figure 8. Registration of medical images
4.6 Surface-to-Surface Registration
With the increasing popularity of LIDAR systems, there has
been an interest in establishing procedures for surface-to surface
registration for change detection applications (e.g., Habib et al., |
2001b). Habib et al. (2004) used LIDAR features as control
information to establish the absolute orientation of 3-D
photogrammetric models. Photogrammetric triangulation |
incorporating tie linear features has been used to derive 3-D
straight-line segments relative to an arbitrary coordinate system,
Figure 9-a. On the other hand, LIDAR linear features have been
extracted by processing the elevation data, Figure 9-b. Finally,
conjugate photogrammetric and LIDAR features were used to
determine the parameters relating the photogrammetric
coordinate system to the LIDAR reference frame (i.c., solve for
the absolute orientation paramcters). The approach proved to be
successful in detecting discrepancies between the involved
surfaces. Such discrepancies can be either attributed to changes
in the object space and/or un-accounted systematic biases in the
data acquisition systems.
(a) (b)
Figure 9. Straight-line features obtained from photogrammetric
(a) and LIDAR (b) systems
5. CONCLUSIONS AND RECCOMENDATION FOR
FUTURE RESEARCH
This paper discussed key issues related to the incorporation of
linear features in photogrammetric applications. First, it has
been established that among the possible types of linear
features, straight-line segments are the most interesting ones.
This can be attributed to the fact that they abundantly exist in
imagery of man-made environments. Also, free-form linear |
features can be represented with sufficient accuracy as à
sequence of straight-line segments (poly-lines). Moreover,
straight-line segments are valuable for the self-calibration of
frame cameras and the recovery of the EOP for linear array
scanners.
We introduced a mathematical model for incorporating linear
features in photogrammetric and medical problems (c.g.
automatic space resection, photogrammetric triangulation,
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