The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
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postprocessing 
Exposure delay 
Unknown, variable 
Given: measurement of the exposure 
delay and examination of delay pattern 
Systematical error, 1-3 m 
Instability of the platform 
No vertical images, due to winds 
and accelerations 
Not given 
Non systematic error, 3- 
5° 5-9 m 
External factors 
DEM (constant height 
value) 
Differences in elevation in the 
area, no DEM available 
Given: application of a better / more 
accurate DEM / ortho rectification 
Non systematic error < 5 
m 
JPG-Compression 
Poor image quality / problems at 
automatic tie point generation 
Given: may be reduced by lower 
compression / more storage space 
Small < 0.5 m 
Wind gusts 
Influences the speed of the 
UAV-> image overlap, block 
stability 
Partly given: await weather with low 
winds 
Large (> 5 m) 
Image motion 
Image motion due to high speeds 
at low altitudes above ground of 
the UAV, No FMC 
Given: use of camera with a large pixel 
size per CCD-element and short 
exposure intervals 
Medium (> 2 m) 
Table 4: Factors influencing the direct georeferencing of UAVs 
6. OUTLOOK AND FUTURE WORK 
Despite the above mentioned problems the system SUSI is 
currently used in the state forestry administration of 
Mcklenburg-Vorpommem quite successfully for a large range 
of forestry applications. Yet further improvements for the two 
Micro-UAV systems are necessary and should eliminate their 
specific weaknesses. The biggest improvement of the system 
SUSI should be an autopilot and an automated electronic flight 
management system in order to perform systematic aerial 
surveys. A better camera with higher resolution and shorter 
exposure interval and the synchronisation between the 
triggering of the camera and the recorded GPS-signal should be 
the first steps of improvement for the system Carolo P 330. The 
second step includes improvements in the autopilot system and 
a translation of the attitude angles of the INS into the 
photogrammetric angles. 
The large application potential of Micro-UAVs is directly 
linked to a precise and economic photogrammetric workflow. 
On one hand the generation of image mosaics, the incorporation 
of images in a GIS and 2D- or 3D-data analysis are based on 
precise geo referencing. On the other hand the effort for an 
aerial survey and the post processing of the data has to be cost 
efficient. It is too early for a reliable comparison of Micro- 
UAVs and common aerial surveys because the development of 
the Micro-UAVs for this kind of applications is still at an early 
stage. 
To sum up, current micro-UAV-systems have a great potential 
for many applications which require up to date data of small 
objects. Efficient geo referencing is a key issue. Therefore it is 
necessary that the developers of the UAVs and autopilots have 
to understand the special requirements of photogrammetry. 
Additionally, photogrammetrists have to develop new methods 
for efficient geo referencing and also use the potential for direct 
georeferencing. 
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