The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B5. Beijing 2008 
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CPU demanding application is the visual GUI of HELIPOS 
with the map layer and the handling of different layers (e.g. 
flight-lines, system position, RT swath, data extend and data 
gaps). Especially performing zoom and pan operations 
(inducing complete screen refreshments) on the map loads the 
CPU up to 30%. 
The performance analysis shows that the current configuration 
can manage and process the different data streams in real-time 
at full data rates. The whole application could even run on a 
single computer, although for safety reasons, a physical 
separation between the vital parts (data logging and storage) 
and extended functionality is recommended. 
8. CONCLUSIONS AND OUTLOOK 
While previous research focused on determining ALS data 
quality (i.e., the homogeneity, completeness and accuracy) by 
post-processing analyzes, in this contribution we proposed, 
designed and tested an approach that achieves good part of such 
evaluation in the real-time. By enabling such analyzes in the 
flight, the operator is immediately informed if part of the 
mission does not correspond to its requirements. From our 
experience, such information is critical in complex flight 
missions using helicopters and/or oblique orientation of the 
LiDAR sensor. 
We presented modular software architecture where the data 
acquisition components are tied to a specific hardware while 
those related to data processing are not. The architecture is thus 
portable to different systems with the adaptation limited to the 
data acquisition components. If needed, the design is also 
scalable to different data throughput by running some modules 
on separate processors. 
The empirical testing was limited to GPS data in point 
positioning mode. Hence, the obtained accuracy of the real-time 
laser point-cloud reflected that of GPS and stayed at the metric 
level. Nevertheless, such accuracy proved to be largely 
sufficient to control the completeness of the scanning mission in 
terms of its coverage and density. 
Our future efforts will focus on employing different strategies 
to improve RT positioning accuracy. These methods are of 
interest for controlling partially or completely the integrity of 
the GPS code and/or phase measurements before the post 
processing. This information will be also pre-requisite for the 
extended quality analyses that incorporates rigorous error 
propagation considering all measurements, system components 
and laser incident angle as described in (Schaer et al., 2007). 
ACKNOWLEDGMENT 
This work was mainly funded by the Swiss Commission for 
Innovation (CTI/KTI Project 7782.1 EPRP) in collaboration 
with SWISSPHOTO AG. 
The GIINAV-Module is licensed software to EPFL by the third 
author. 
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