5. EXPERIMENTS IN DIGITAL VIDEO IMAGING AND PROCESSING FOR PHOTOGRAMMETRY
Video image experiments in Photogrammetric Research at NRC date back to
1976. An early 100x100 pixel solid state imager (Fairchild, left side of
Fig. 2a) and the first commercial CCD video frame memory, Real, 1986, were
employed in experiments in subsequent years for various purposes, but
initially for a digital profile to contour converter and display, Real,
1976. The work was never carried beyond the feasibility stage and results,
while promising, remained unpublished.
Video image transfer trials (in cooperation with Canadian Marconi,
1980-82) were conducted on the NRC Anaplot. The system consisted of an
analog video substitute for the stereo optical system with electronically
injected measuring marks adjustable as to intensity (light to dark), size
and position. Beamsplitters directed the stereo Anaplot images onto a pair
of COHU 7120 series high resolution 1000 line Vidicon cameras, the signals
from which were relayed to a separate room and displayed on Tektronix 634
black and white high resolution 5" monitors which were viewed with an
optical stereoscope. A separate set of handwheels, footwheel and terminal
port completed the remote Anapict workstation. Unpublished results show
that in spite of quite inferior stereo video images, compared to the optical
ones, relatively precise measurements were possible. It was considered
important that digital image processing be introduced into the system to
expand capability well beyond simply emulating an optical image transfer
system. A feasibility system evolved subsequently, partly from in-house
development, out of necessity, and partly from commercial products, Real,
1985. Results of the progress have been published since 1982, with some
updated examples below. A complete stereo image acquisition and digital
processing system for demonstration with the NRC Anaplot is being prepared.
An example of default window processing due to processing speed limits is
demonstrated in Fig. 3a. For example, if the entire image exceeds the
available processing rate, either frame update rate may be reduced, and/or
Fig. 3(a) Image with windowed portion transformed by convolution kernel
-12 -12- 8
12 O -12| (Real, 1984b).
-12 -14 12
-12 -12 - 8|? -12.-12.-.8
(b) Window: kernel 12 O -12] ; Border, kernel 12 0 -12
-12 -14 12 -14 -14 12
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