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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