International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004
that of most of the turnkey commercial systems. In other words,
the cost of a development leading to a modular fully digital large
scale mapping system of decimetre accuracy has been justified.
Equipment Cost [US$]
Digital Camera 30'000
GPS receivers 13000
IMU (LN-200 A1) 20'000
Lidar (LMS-Q1401-60) 35'000
IMU interface 3'000
Frame 2'000
Computer 2'000
TOTAL HARDWARE COST: 105'000
Table 6: System equipment cost.
OPERATION GEOREFERENCING PRODUCTS
MODES GCP Tie Navigation | DTM Ortho-
points ' photo
AT eM eM - e M eA
AT-GPS - eM € A e M eA
Direct
(CCD/GPS/I - - 9A eM eA
MU)
/
aii E 3 eA eA e A
/ x
Table 7: Comparison of processing tasks (M: manual, A:
automated) for different modes of system operation.
5. CONCLUSIONS AND OUTLOOK
The development of a dedicated airborne mapping system
(HELIMAP) was initiated as a response to the country's needs for
natural risk management and monitoring. The objective was to
design a self-consistent system, easily deployable on a helicopter
that can provide digital surface mapping of an area of interest:
e With a high precision (0.2m),
e With a high resolution (<1m?),
e Shortly after the flying mission (few hours).
This information is essential for risk assessment and monitoring of
natural hazards such as avalanches, debris and water flows,
floods, as well as forestry management. Evolution of the system
followed the emergent technologies used in modern mapping and
remote sensing. First, the analogue camera has been replaced with
a CCD sensor to increase the image quality. Second, airborne
laser scanner was added to drop the need for photogrammetric
stereoploting.
At the same time new approaches were investigated in the direct
georeferencing, especially with respect to boresight and lever arm
calibration. It was concluded that surveying lever arms in
laboratory is superior to in-flight calibration, which should be
reserved for determining boresight and parameters of interior-
orientation. Moreover, the significance of considering temporal
correlation in the IMU/GPS data with respect to the boresight
determination was highlighted in a newly developed procedure.
The mapping experience with the system in CCD/GPS/IMU mode
has proven its unique performance in terms of flexibility, cost and
accuracy (<20cm). To improve the production time and hopefully
fully automate the mapping process, a Lidar has been integrated to
the system. However, the evaluation of the new
ALS/CCD/GPS/IMU operation mode has not yet been finalized.
ACKNOWLEDGEMENTS
We would like to thank Ulrich, Weismann * Rolle AG for their
active contribution to the system conception and flight expertise.
Many thanks to Air Glaciers helicopter company for their
availability and flexibility during the frame design and test flights.
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http://www. vnrsa.ch/products/LN200.htm
