International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part Bl. Istanbul 2004
For GPS post-processing, data from a base station of the
Austrian Academy of Science in Graz was used. This base
station has a distance of six km from the centre of the project
area. The number of satellites was between five and seven with
a P-DOP around two.
The GPS post-processing was done with GrafNav of Waypoint
Consulting, the GPS/IMU processing was executed with
AEROoffice, the automatic tiepoint measurement with
MATCH-AT from INPHO and the AT with B/NGO of GIP.
6.1 Guidance accuracy
To check the correct timing of the trigger pulse and the
feedback signal, the difference between the planned photo
position and the measured position of the camera at the instant
of exposure was compared.
Figures 7 and 8 show these differences for the flight direction
and the perpendicular direction, respectively (for the east-west
lines). The comparison shows a RMS of about 2m for the flight
direction, and a RMS of about 4m for the perpendicular
direction.
The value in flight direction is dominated by the GPS realtime
accuracy for the navigation. The position difference
perpendicular to the flight direction reflects the skills of the
pilot to stay on the flightline indicated by the CONS.
20
RMS = 205m
15 4 ; mean = -1.75m
min. =-7.67m
10 re = ES ~ max. - 306m | |
0 100 200 300 400
Fig. 7: Difference between planned and flown photo-position in
flight direction, number of photos vs. difference in
meters.
20 RMS = 419m
15 + mean = 0.60 m
min. =-9.51 m
10 + max. = 18.02 m
5 À
0 4
-5 +
-10 |
-15 1
-20
0 100 200 300 400
Fig. 8: Difference between planned and flown photo-position
perpendicular to the flight direction, number of photos
vs. difference in meters.
These results illustrate the capability of the system to
reproduce photos within a position accuracy of some meters
(“pin pointed aerial photography”).
176
6.2 Boresight alignment
The relative orientation between the IMU coordinate system
and the coordinate system of the camera has been determined
with help of an ISO of a sub-block of the project area. For this
extended AT a small block of 30 images in the south of the
area was used. In this calculation only every third image was
used, resulting in a forward overlap of app. 70%.
With this boresight AT the misalignment angles have been
calculated with an accuracy of app. 0.7 deg for roll and pitch
and 2.6 deg for the heading angle. The datum shift to the local
coordinate system was calculated as well.
6.3 Direct georeferencing (DG)
The results of the boresight alignment were used to orient the
images in a block 2 km apart the area of the boresight AT.
The positions of known GCPs were determined with help of
the directly measured EO-parameters. Deviations between
GCP coordinates and measured coordinates over a set of 8
points were investigated as a final proof of the quality of direct
georeferencing. Horizontal deviation of about +/- 14 cm in east
and north direction and deviations of the z-component of the
position in a range of +/- 23 em could be observed.
For the given mission parameters, these values are within the
expected accuracy range. The setup of images was done on the
SUMMIT Evolution of DAT/EM and found to be free of
vertical parallaxes.
7, CONCLUSIONS
We have shown the integration of the large format digital
aerial camera ULTRACAMnp of Vexcel and the CCNS4
guidance and sensor management system together with the
GPS/IMU option AEROcontrol of IGI mbH. A test project was
successfully flown and results were presented.
The novel option of the digital camera to transit from the
traditional 6096 forward overlap to a highly redundant set of
images with forward overlaps of up to 90 % was discussed and
the need to automate the processing of such datasets was
mentioned.
8. REFERENCES
Cramer, M. (2003) Erfahrungen mit der direkten
Georeferenzierung, PFG 2003(4), pp 131-137
Heipke, C. et al, (2001): The OEEPE Test on Integrated
Sensor Orientation, OEEPE Workshop on Integrated Sensor
Orientation, Hannover, Germany
Kremer, J. (2001): CCNS and AEROcontrol: Products for
Efficient Photogrammetric Data Collection, Photogrammetric
Week' 0l, Fritsch/Spiller (Eds. Wichmann Verlag,
Heidelberg: 85-92
Kremer, J. (2002); CCNS / AEROcontrol - an Integrated
GPS/IMU System for Direct Georeferencing of Airborne Image
Data, Symposium Gyro Technology 2002, H. Sorg (Ed.),
Universität Stuttgart: 16.0 -16.9
Kremer, J. & Kruck, E. (2003): Integrated Sensor Orientation -
Two Examples to show the Potential of simultaneous
GPS/IMU and Image Data Processing, Proceedings of the
ISPRS Workshop Working Group 1/5 “Theory, Technology and
