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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