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4.2 Photogrammetry Operation Process
4.2.1 Targets
Targets in photogrammetry operation refers to put coded markers and uncoded
markers on the object which would be measured.
The requirements for pasting uncoded markers are as follows:
The spacing between each two mark points is 30mm to 250mm, which is
determined according to the actual situation of the workpiece. If the surface
curvature changes little, the distance can be appropriately larger, and the
maximum distance is 250 mm. If the workpiece features more curvature changes,
the distance can be appropriately reduced, and the minimum distance is 30 mm.
As shown in Figure 4-1.
Figure4- 1 Pasting uncoded markers
Note that the mark points should be randomly distributed to avoid regular
arrangement (Figure 4-2). Because the scanner is relatively positioned by
identifying the position structure composed of the marker points, if the marker
points are arranged regularly, the probability of reading errors at the marker point
position is increased, thereby causing data acquisition errors.
