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The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008 
Figure 6: Pedestrian crossing 
From each pedestrian crossing, a resolution measurement is 
extracted, taking the mean of several values obtained over 
different parts of the crossing, in order to minimise the effects 
of noise. Furthermore, frames with a high number of crossings, 
placed horizontally and vertically, have been chosen in order to 
compare the results that we obtain with the theoretical 
estimations that we already have. 
The Figure 7 and 8 show the value of resolution obtained from 
the application of the software in different pedestrian crossings, 
based on the distance to the centre of the shot, compared to the 
theoretical values of resolution in flight and cross-flight 
direction, respectively. 
Figure 7: Resolution cross-flight direction 
Figure 8: Resolution flight direction 
7. CONCLUSIONS 
DMC digital images prove to have a big improvement in terms 
of image correlation reaching a matching accuracy of 1/10 th of a 
pixel. In aerotriangulation check points showed that an 
accuracy of 1/2 pixel in the horizontal components and 2/3 of a 
pixel in the vertical component can be routinely archived in 
production flights. In this study, however, the high accuracy in 
the correlation of digital images is not reflected in the 
horizontal accuracy because the check points are measured 
manually without any automatic or semiautomatic support. 
Despite of the worse b/h factor a small improvement in the 
vertical accuracy has been observed. This is due to the fact that 
most of the check points are measured in images from different 
strips (flown at 25% side lap), where the (larger) “side lap b/h 
ratio” compensates the worse b/h in flight direction. 
Automatically derived DEMs from digital and analog images 
result in more or less comparable accuracies with small 
advantages for the digital camera. Digital images also allow 
smaller grid spacing down to the size of 5 pixels. The 
comparison with L1DAR data proves a vertical accuracy of up 
to /2 pixels in flat areas without vegetation and buildings. In 
urban areas the accuracy is considerably worse (approximately 
2 pixels), because the DEM grid points do not well represent 
the height discontinuities at the edges of buildings or other man 
made objects. 
From the steroplotting point of view, the conclusion is that the 
use of digital images allows digitizing more information, 
extending the flight period and introducing more comfort in the 
steroplotting process. Although there is a slight loss of the relief 
feeling, and there is a small decrease in the height accuracy, it 
is not important enough to introduce degradations in the final 
products. Finally, more automatic tools are needed to optimize 
image display and management. Stereoplotting check points 
showed that an accuracy of 1.1 pixels in the horizontal 
components and about 1.5 pixels in the vertical component can 
also be routinely achieved in production projects. 
Concerning the resolution of DMC digital images in the paper 
absolute resolution measures have been generated from a 
Siemens star target whose dimensions are known. The 
measurement FWHM which is extracted from the LSF function 
provides a specific quantification of the resolution of the system, 
coherent with techniques of resolution evaluation, using USAF 
targets. This very same methodology can also be applied to 
analogues images (Alamus et. al, 2005). The results then 
obtained, showed the greater resolution power of the DMC, in 
front of the film cameras. 
REFERENCES 
Alamús, R., Komus, W., Palá, V., Pérez, F., Arbiol, R., Bonet, 
R., Costa, J., Hernández, J., Marimon, J., Ortiz, M. Á., Palma, 
E., Pla, M., Racero, S., Talaya, J. 2005: Validation process of 
the ICC digital camera. ISPRS Worshop “High-Resolution 
Earth Imaging for Geospatial Information”. Hannover. 
Honkavaara, E., Jaakkola, J., Markelin, L., Becker, S., 2006. 
Evaluation of Resolving Power and MTF of DMC. In 
proceedings of ISPRS Comission I Symposium, Paris. 
ACKNOWLEDGEMENTS 
We would like to thank the hard job done by M. Cabré, J. 
Costa., J. Marimon and A. Serrano for the selection and 
measurement of the check points used in the aerial triangulation 
and stereoplotting accuracy assessment. 
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