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(m)
Y
3,03
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2,68
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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part Bl. Istanbul 2004
Correction RMS (m) Maximum (m)
Method X Y X Y
Parametric | 1,05 1,94 3,45 6,08
RPC 2,70 1.52 5,84 3,14
Table 7. Comparison of RMS and maximum errors over 91
ICPs of parametric model and RPC computation with
10 GCPs
For row IKONOS data for Warsaw areas, a mean positioning
error of 10 m in the Y (orbit direction) and only 2 m in X di-
rection was found in the 35 ICPs.
|. For flat areas (Figure 3.), with a use of DEM of accuracy
5-7 meter ( Z ) and with a use of altimetrical points from
GPS survey for IKONOS images, method RPC enables
achieving accuracy (RMS) of some 1.5 meter irrespective
of a number of GSP used. Even a use of a single 1 GSP
provides for achieving sufficient accuracy. Parametrical
method for this sensor requires a use of at least 9 GCP in
order to achieve nearly the same accuracy.
bo
In case of images achieved from QuickBird (Figure 4.) (for
the same conditions), RPC method gives accuracy (RMS)
of 2 meter, but with a use of minimum 2 GCP. Applying
PM for 8 GCP we can obtain RMS nearly | meter.
3. For mountain areas (of de-leveling 500 meters) with iden-
tical DEM for IKONOS images, RPC method gives RMS
of some 1.5 meter. With a use of PM, minimum number of
GCP is 7, and it gives the same accuracy.
4. For QB imaging, using a method type RPC, we can obtain
RMS slightly above 3 meters with a use of at least 2 GCP.
At the same time, with a use of MP of minimum number of
GCP equal to 9, we can improve the accuracy even twice.
4. CONCLUSION
Commercial PCI software used enables VHR ortho-adjustment
with the use of methods RPC and PM for different numbers of
GCP and available DTM, and to achieve accuracy in VHR or-
tho-adjustment process of nearly 1 meter. At the same time we
have to be very strict when determining the following:
a. GCP points should be very precisely selected, measured
and interpreted in the process of ortho-adjustment.
b. The test show that the parametric models demonstrating
error stability for QuickBird orthorectification, with min.
8-10 of GCP. While non-parametric models is less precise
for that system.
c. The parametric approach is very sensitive in accuracy for
distribution GCPs in range of 7-10.
d. For IKONOS data non-parametric (RPC) approach has
better stability and needs less GCPs points for
orthorectification.
e. The input values of Z in the process of ortho-adjustment
on the basis of used points GCP "read only " from DTM or
GPS survey, it gives almost the same accuracy for ortho
-rectification process.
f. For flat areas it is enough to apply DEM of accuracy in
range 5-7 meters for IKONOS imaging with minimum
number of GCP, achieving accuracy of some 1.5 meter. At
the same time for QB imaging the application of paramet-
ric method brings better results.
ga
Similar recommendations apply to mountain terrain. Using
more precise DEM we can achieve a considerable im-
provement of accuracy.
h. The geometric limitation is the very often limited quality
of control points in the images.
5. ACKNOWLEDGEMENTS
The author thank INTA SPACTURK and European Space Im-
aging for providing IKONOS images, DigitalGlob for provid-
ing the QuickBird images and ImageSat Int. for providing
EROS images, respectively to do research in Poland.
6. REFERENCES
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