In: Wagner W., Székely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010, IAPRS, Voi. XXXVIII, Part 7B 
3) Location models improvement using a space-triangulation 
process and model parameters correction, including a possible 
DEM refining. 
Moreover, thanks to the high agility and the precise pointing 
capability of the Pleiades-HR platform, it will be possible to 
acquire several successive adjacent strips within a unique pass 
over a targeted area. 
Thus, the Pleiades-HR ortho-mosaic product will provide 
end-users with an image of larger size, as being the 
result of a seamless patchwork of individual strips. The 
output coverage may reach up to 10 000 km 2 and even 
more, according to the length of the neighbouring strips 
and the tolerated B/H ratio between acquisitions. 
Figure 5: Pleiades-HR agility and mosaicking capability 
The automatic mosaicking process relies on two geometric 
refining phases (as described above). The same method is used 
for: 
Phase 1: Absolute refining of each data strip location model 
using Reference3D™ data. 
Phase 2: Relative and finer improvement of location models 
using overlapping areas of adjacent strips (350m to 3.5km) and 
Reference3D™ DEM. The evaluation has been done using 
aerial images simulating Pleiades-HR acquisitions and the 
results were excellent. Thanks to the first phase, the absolute 
accuracy is less than 2.5m (0.5 Reference3D™ pixels). The 
second phase refines the relative model with respect to the very 
high resolution of the acquisition (<0.5 pixels HR). 
This product represents the successful realization of the 
Pleiades-HR mission since it takes advantage of the main 
characteristics of the system: agility and high location 
precision. The automatic mosaicking process relies on 
automatic tie point selection (Baillarin 2004) and geometric 
models refining phases followed by local radiometric 
homogenisation and stitching phases (seam-less line 
computation). 
Figure 6: Pleiades-HR mosaic (and stitching line) 
5. CONCLUSION AND OUTLOOK 
The Pleiades-HR image processing is very complex (about 50 
times more complex than SPOT5) and therefore time 
consuming, especially for geometric corrections. Nevertheless, 
a ground processing unit has been successfully developed to 
handle up to an average of 200 products a day for the main 
civilian UGC in Spot Image premises. Based on a multi 
clusters architecture (IBM Blade Center™) linked by high 
speed Fibre Channel to a Storage Area Network, the Pleiades- 
HR infrastructure is highly scalable for the different centres 
needs (including local receiving stations). In particular, for 
emergency needs, pan-sharpened ortho-rectified products 
(20x20km 2 ) are processed in less than 45mn and mosaic 
products (60x60km 2 ) in less than 140mn. 
The realization of the Pleiades-HR ground segment is once 
more the opportunity to demonstrate that a global optimization 
of the system from board to ground design must be considered 
in order to relax requirements of on-board architecture and 
lower the overall cost of the mission. 
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Baillarin S, 2006, Remote Sensing Image Ground Segment 
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Kubik P, 2005, PLEIADES image quality from users’ needs to 
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Unser M, 1999, Splines: A perfect fit for signal and image 
processing, IEEE Signal Processing Magazine, November 
1999. 
De Lussy F, 2006, Pleiades-HR image system products and 
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Tao C., Hu Y., 2001, The Rational Function Model: a tool for 
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