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4.4 Performance 
As we are planning to execute the extraction of traffic 
parameters on the 3 x 16 Mpix rgb-images obtained from the 
3K camera in near real time, we have to focus upon 
performance. Therefore, tests on road and vehicle detection as 
well as vehicle tracking were performed on actual standard 
hardware consisting of a dual-core PC with a CPU frequency of 
1.86 GHz and 2 GB RAM. Road extraction on a typical 
motorway takes less than 30 s for one nadir and two side-look 
exposures in total. Vehicle detection on these three images 
needs 25 s of calculation time on the present system. In 
comparison, car tracking is quite fast, consuming only 15 s for a 
tracking of 3 x 15 cars over an image sequence consisting of 3 x 
4 images. Moreover, the pure calculation time for cross 
correlation is 30 ms per vehicle for a tracking through the whole 
sequence. In total, it costs 70 s to analyse the traffic within one 
image sequence. That means, assuming a break of 7 s between 
each image “burst” (which would result in a overlap of 10 % 
between two image “bursts” at a flight speed of 60 m/s and a 
flight height of 1000 m), we have a time overhead in the 
processing chain for traffic monitoring of a factor of 10. 
However, the prototype of our processing chain is built up still 
modular, which means that each module in the chain reads an 
image from hard disk into memory, performs an operation, and 
at the end writes a new image to hard disk. We estimate to 
halve the overhead by reducing hard disk read/write. Further 
progress in reducing calculation time could be made by using 
actual hardware with high performance quad core CPUs. 
5. CONCLUSIONS 
Despite the large amount of incoming data from the wide angle 
camera system, we are able to perform traffic data extraction 
with a high actuality. Thereby, high accuracies for velocities (5 
km/h), good correctness in vehicle detection (79 %) and in 
vehicle tracking (90 % of detected vehicles) is reached. Hence, 
the investigations show the high potential using aerial wide 
angle image series for traffic monitoring and similar 
applications, like the estimation of travel times or the derivation 
of other relevant traffic parameters. Moreover, the data 
processing speed can be improved in future by converting the 
modules of the processing chain into tasks which hand over 
pointers to images stored in the RAM instead of reading and 
writing them on hard disk, as done by our prototype. 
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