I 1 • • ■
The International Archives of the Photogrammetry. Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008
258
equipped also with a LIDAR Leica ALS50. This selection has
been done after a detailed analysis of the actual problematic of
process for orthoimage generation in urban areas in which the
company Altais, S.L. has participated. Figure 9 shows in one
way an example of one orthoimage obtained using classical
methods of orthorectification (Ground Ortho), and on the other
way, the orthorectification resulting from using the program
ALTAIS-LRTO, in an area in Burgos with a flight from year
2007.
Figure 9.- Example of True Orthorectification using the
solution Altais-LRTO.
6. CONCLUSIONS
A new method of orthorectification was developed giving
notable improvements compared with commercial systems as it
integrate analysis of multiple incidence algorithms:
• Most Right Method. It is an orthorectification and
mosaiking method based in spatial resection of the
perspective ray of most verticality for each terrain point,
i.e. it uses the photography of better perspective for
each point.
• Nadiral Profile Method. Equally it is an
orthorectification and mosaiking method that resolves
the spatial resection of the perspective ray free of
occlusions for each point in the terrain. This method,
applied to the true position of sun, also determines the
shadow areas of the orthophotograph, which can be
treated radiometrically, to extract detailed information
within the shadow.
The system Altais LRTO resolves problems well known in
orthophotography, such as the appearance of stretching areas
due to the compression of the input image, where the
relationship GSD input /GSD output <l is not true, the true
orthorectification of elements within the DSM with no need to
use additional volumetric information, not just presenting these
in its correct position, with no leaning, but automatically
completing the occluded information due to this leaning with
the appropriate information showed under the influence of
shadows.
ACKNOWLEDGEMENTS
The results exposed in this work belong to the ones obtained in
the research project “Development of a true orthoimage
generation software as a base for urban territorial information”
(Proyecto DATOS) (FIT-340001-2006-41) belonging to the
National Plan for R+D+I within the PROFIT program of the
State Secretary of Telecommunications and for the Information
Society of the Ministry of Industry, Tourism and Commerce.
These activities form part of the R+D+I activities of the
research group of “Photogrammetric and Topogrammetric
Systems” of Jaén University partially funded by the regional
government of Andalusia through the R+D+I Regional
Program.
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