. Correction of mismatching points in low contrast area
+ With the method of parallax smoothing to detect blunders
2.5 Generation of DEM
After correlation procedure a parallax grid regularly arranged
on left epipolar image can be formed, and then forward intersection
is needed to calculate space coordinates from epipolar line
coordinates airectly. For generation of digital elevation model
a simplified method for interpolation is used in sCDANS.
2.6 Contouring and digital rectification
Based on digital elevation model we can derive contour lines in
raster data format and rectify image digitally. Then, it is quite
easy to superpose these two files with the "OR" operation for
getting a final result -- orthophoto with contour lines.
2.1 annotation
Annotation is one of important parts of a map. For the purpose of
making annotation, we should establish a "data bank" for digital
numbers and characters (chinese characters are also contained) by
scanning and digitizing a lettering composite film, which is de-
rived from photocomposer. Once the "data bank" has been established
any character needed for annotation can be picked out and put it
onto a correct position. The digital numbering annotation for index
contour line (fig.4.) has shown this capability successfully.
A software "adapter" has also been developed for using the DEM
generated by SODaMS to produce a data tape of image coordinates,
which can be directly used to drive Wild Avioplan OR 1 for orthopho-
toproduction.
2. RESULTS QF PEHFORMANCE TESTS FOR SODAMS
For the purpose of testing the performance of SODAMS, we have chosen
four models of good quality image and moderate relief, which were
taken from Wild RC - 8 camera. Some parameters concerned are shown
as follows:
focal length z210.25 mm
photo scale =1:10000
maximum altitude difference within a nodel > 200 m
All of those four models are processed by the SODANS. The ortho-
ptioto with contour lines of one model is shown in Figure 4. Sever-
al index contour lines have been marked by digital numbering on
suitable places.
For tne purpose of assessing heignt accuracy of this digital auto-
matic mapping system, we use the known planimetric coordinates X,Y
of check points as input data. The an interpolation for their
- 678 -
