1S
nd
Automatic determination of réseau targets is
performed by a precise line detection method, which
calculates line points of the target legs with subpixel-
accuracy. The total precision of the target location
amounts to approximate 0.1 - 0.2 pixel [LUHMANN 1986al.
The programs for sensor control and image processing
operations are written in Turbo-Pascal 3.0 installed
on a personal computer compatible to IBM-PC or XT.
Based on the scheme of Fig.5 the RS system can be
combined with a graphics tablet for generating
scanner control values and supporting automatic point
measurements. Furthermore the whole system is completely
compatible to the Rolleimetric MR2 multi-image
restitution system.
4. Applications and results
— — — — —— — 9À—— M — 9 À ——À — M — i — e—— — M — U— — e — e — e
On principle the Rolleimetric RS1 can be used to digitize
any kind of picture for purposes like medical applications,
earth sciences, remote sensing or any field of pattern
recognition and image processing. Color filters inserted
in the light path enable different spectral band digitizing.
Furthermore the RS1 system can be used as digital
mono-comparator. Depending on the desired accuracy, a
suitable projection scale can be choosed. The image
coordinates are measured interactively by cursor control
on a video display.
An extended software system is able to perform
automatic measurements of those points, whose pattern
structure is known (e.g. fiducial marks, réseau crosses,
marked points). Initial coordinates of these points
are generated by an auxiliary measuring system (graphic
tableau, display) or by an approximate orientation
parameter set [LUHMANN 1986b].
The following two examples of photogrammetric evaluations
show reliability and accuracy of the RS1 system.
First, a calibrated grid is measured automatically
performed by the same procedures as used for sensor
orientation. À linear affine least square fit of
located control targets leads to a standard error
of unit weight of +1.5 um (maximum discrepancy 2.5 um)
using a scan-réseau grid size of 2.5 mm (projection
scale 1.7:1).
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