International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B2. Istanbul 200
APP - AT1 APP - AT4b
RMS RMS X RMS Y RMS RMS X RMS Y
Mean 0.114 -0.071 0.084 0.140 -0.096 0.101
St. Dev. 0.035 0.036 0.030 0.015 0.010 0.017
Table VII. Statistical parameters of the comparison from the ortophotos for Catania project (in meters)
results of the comparison between the coordinates of some
points located over the APP orthophoto (fig. 6) with those of
the same points derived from the orthophotos related to other
two configurations; the average discrepancies are in the order of
10 cm.
4. CONCLUSIONS
Results obtained in both tests confirm precision and reliability
of this innovative technique. The use of the direct
georeferencing, also for production of digital large scale
orthophotos, seems to insure geometric accuracy required by
map standards.
Several check were carried out comparing the exterior
orientation parameters derived from GPS/INS sensor (APP)
with those computed by AT according to different
configurations; particularly the following configurations were
considered: AT with APP data and tie points (AT1); traditional
AT with tie-points and GCPs (AT2); AT with APP data, tie-
points and 1 GCP (AT3a) or 4 GCPs (AT3b). Besides, for one
of the two available flights, a calculation was done considering
only the perspective centre position and a small number of
GCPs, respectively 1 GCP (AT4a) and 7 GCPs (AT4b).
Discrepancies between these values and APP ones always result
very small, both with regard to the perspective centres and the
orientation angles.
The accuracy of the different AT configurations was computed
using some points surveyed by GPS method and employed as
CPs in the AT procedures. The residuals are always resulted
within geometrical tolerance required by National map
standards for digital orthophotos produced at scale of 1:2000
and 1:200.
A final check was done comparing the othophotos produced
from APP data with those related to ATI and AT2
configurations for Palermo and ATI and AT4b configurations
for Catania. The results show RMS in the order of few
centimetres for both projects.
Using direct exterior orientation parameters and some tie-points
(ATI configuration) it is possible to get results equivalent to
those obtained with use of some GCPs. However such
procedure does not permit to check the presence of systematic
or gross errors. The use of a certain number of CPs seems to be
essential to control the geometric accuracy of data also with
reference to national map standards.
REFERENCES
Cramer M., 2003. GPS/inertial and digital aerial triangulation —
recent test results. In. Photogrammetric Week 2003, Fritsch
(ed.), Wichmann Verlag, Heidelberg, Germany , pp. 161-172.
Cramer M., Stallmann D., 2003. On the use of GPS/inertial
exterior orientation parameters in airborne photogrammetry. In
Test Report and Workshop Proceedings, OEEPE Official
Publication n. 43, pp. 109-120.
Forlani G., Pinto L., 2002. Integrated INS/GPS systems:
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Workshop Proceedings, OEEPE Official Publication n. 43, pp.
85-96.
Galetto R., Casella V., 2003. An Italian national research
project on inertial positioning in photogrammetry. In.
Proceedings International Workshop WG1/5 “Theory,
Technology and Realities of Inertial/GPS Sensor Orientation”,
Barcellona, Spain.
Galetto R., Casella V., 2004. Direct Georeferencing Activities
in Italy. PE & RS, n. 1/2004.
Heipke C., Jacobsen K., Wegmann H., 2002. Analysis of the
results of the OEEPE test Integrated Sensor Orientation. In Test
Report and Workshop Proceedings, OEEPE Official
Publication n. 43, pp. 31-45.
Mostafa M., Hutton J. 2001. Direct Positioning and
Orientation Systems. How Do They Work? What is the
Attainable Accuracy?. Proceedings ASPRS.
http://www.applanix.com/html/gps inert resource.html
(accessed April 2004)
Jacobsen K., 2000. Potential and limitation of direct sensor
orientation. In. /nternational Archives of Photogrammetry and
Remote Sensing, Vol. XXXIII, Part. B3, Amsterdam, pp. 426-
435.
Jacobsen K., Wegmann H., 2002. Dependencies and problems
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ACKNOWLEDGEMENTS
We would like to thank:
- CGR from Parma, for the collaboration on the
photogrammetric operations related to Catania project;
- prof. Giuseppe Mussumeci, from the University of Catania,
for the cooperation in the GPS survey.
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