EuroSDR Projects - Host Ireland

calibration and exterior orientation information (Figure 3-3). Photogrammetrically measured data was
corrected and improved by an AutoCAD 2000 system. All measurements and modelling was
performed by an unexperienced person.
After import of the digital aerial images in the digital station using the given camera calibration and
exterior orientation data, the automatic interior orientation of each image was performed in order to
achieve the necessary transformation parameters from pixel to image coordinates. The quality of the
exterior orientation of each stereo pair was checked for existing y-parallaxes and by comparing the
measured and given control points. If the exterior orientation was accepted, each building was
measured manually by the operator using the software module Feature Extraction of SOCET Set. The
operator could select three different roof types (flat, peaked and gabled). The measurement sequence
of the peaked roof points is illustrated in Figure 3-4. The operator first measured the points at each
roof corner (points 1, 2, 3), then the fourth point at the roof top and finally one point at ground
elevation. For gabled roofs the operator measured the point sequence 1, 2, 3 and 4 clockwise, the two
top points (5 and 6) and finally one point at ground elevation (Figure 3-5). Feature Extraction (Auto
Create Mode) automatically creates the remaining sides of the buildings based on the value specified
for the ground. Complex features were broken down into simpler components, which were later
combined in AutoCAD. Finally, the measured data was transferred to AutoCAD 2000 for the
correction of some measurements and for modelling of the complex buildings.
Figure 3-3: Workfow of photogrammetric data processing using SOCET Set on the DPW770.
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