277
Table 3 shows the average mean square error in X, Y of the
orientation. It is clear that considerably accurate results were
obtained for satellite image orientation, so the accuracy of
image orientation has little effect on generating epipolar
imagery.
3.5 Results and analysis
k The result of experiment 1 shows that no big differences
exist between the coordinates obtained by the forward and
inverse RPC models and extracted initially. This outcome
indicates that the accuracy of forward and inverse RPC models
is precision reached.
2 Experiment 2 is carried out to generate the epipolar lines of
satellite stereo images. It was found that the vertical parallaxes
of the conjugate epipolar lines are not more than 1 pixel by the
means of manual visual interpretation either of across-track
stereo pairs or along-track stereo pairs. In which , along-track
stereo pairs include the data from the same satellite sensors and
different sensors.
3 > Accuracy results presented and compared in Table (2)
shows that the RMSEs in SPOT-HGR imagery and IKONOS
imagery was 0.253 pixel and 0.027 pixel. This result is very
good. But, the RMSEs in Radarsat imagery and SPOT-Radarsat
imagery are comparatively large.
4. CONCLUSIONS
Finally, conclusions and recommendations for further research
were presented.
In the first experiment, the conjugate epipolar lines generated
by the RPC model are highprecision. It conforms with accuracy
requirement that use RFM model by way of sensor model.
In the second experiment, for the five pairs of images, the
vertical parallaxs of the conjugate epipolar lines are not more
than 1 pixel by the means of manual visual interpretation as is
shown from Fig(l) to Fig(7). But in the Accuracy Assessment
Section, accuracy presented and compared in Table (2) shows
that the RMSEs in SPOT-HGR imagery and IKONOS imagery
are small, but in Radarsat imagery and SPOT-Radarsat image-
pairs are comparatively large. For the radar imagery, it’s
radiometric and geometric characteristics are special, and
proper conjugate epipolar lines are inexistent. The author just
to simulate its epipolar geometry in this method. The result
shows that there is no means of generating epipolar imagers of
radar by extended epiolar model.
The epipolar resampling approach presented in this paper is
based on the projection track method and using the RPC model
as sensor model. This method is, therefore, appropriate for
optical imagery such as SPOT and IKONOS imagery. In the
practical experiments, it was shown that accuracy of epipolar
generated better than half a pixel was achieved by the proposed
approach. But for the SAR imagery, this method is not
applicable.
Desirable future work related to these methods includes:
1. In this paper, the method of accuracy assessment is an
interior accuracy; it is not strict enough to test the
precision of entire epipolar line. The rigorous method is
matching a point on one image to the other to obtain the
conjugate point, and calculating the distance between the
obtained point to the corresponding epipolar line.
2. There is no need to resample the entire image in actual
production, at present, Mapping software only resamples
the area on the current Windows for the real time, so the
local epipolar is the next step.
3. The experiments in this paper do not establish the relation
between the resampled imagery and initial imagery, that
is to say, for the point on the resampled image, its
location on the initial image is unbeknown. So this is also
in the direction of future efforts.
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ACKNOWLEDGEMENTS
During the research we gain lots of help from others. Thanks
are due for the support from the National Basic Research
Program of P. R. China (No:2006CB701302), the Natural
Science Fund of P. R. China (No:40601084 and No:40523005),
the Open Research Fund Program of State Key Laboratory of
Satellite Ocean Environment Dynamics (No:SOED0602), the
Open research subject of Key Laboratory of Geo-informatics of
State Bureau of Surveying and Mapping, China International
Science and Technology Cooperation Project: High-Resolution
Stereo Mapping Satellite: Field Geometric Calibration and
Application(No.: 2006DFA71570),the Open Research Fund
Program of the Geometries and Applications Laboratory,
Liaoning Technical University (2006004) .With those help,
our research is able to go along propitious.
