21. Helava, U.V. 
Hornbuckle, J.A. 
Shahan, A.J. 
United States 
ON DIGITAL PROCESSING AND ANALYSIS OF IMAGE DATA 
Digital computers can be used to perform different operations on image data. This paper describes several such 
techniques, including the use of Fourier and Hadamard transforms, and digital filtering. Image correlation 
processes also are amenable to analysis and implemention in the digital domain. Direct multi-level correlation 
is shown to be superior in practice to several other techniques. The relatively greater importance of high signal 
to noise ratio over high-bandpass for optimum correlation is also shown. 
22.  Hobbie, D. 
Germany (F.R.G.) 
NEW ACCESSORIES FOR THE GZ-1 ORTHOPROJECTOR 
During 1969, Carl Zeiss of Oberkochen introduced two new accessories for the GZ-1 which since then have 
come into extensive use. 
The ‘Optical Interpolation System’ is used in stripwise rectification where it permits an additional affine 
rectification within the strip. The elements of the image are initially projected on a fiber-optics ring whose 
surface includes ground slope normal to the scanning path up to +35". At the bottom of the ring, which is in 
contact with the film that is to be exposed, a section of the image will undergo affine rectification. This improves 
the horizontal accuracy of the orthophoto and eliminates mismatches. 
The *Electronic Contourline' plots contour lines simultaneously with the exposure of the orthophoto. The line 
width can be varied for emphasis. With this accessory it is no longer necessary to derive the contour lines 
manually, as required with ‘dropped lines’. Another advantage over dropped lines is that the vertical 
information contained in the profiles is much better utilized by using a cathode ray tube to scan the contours. 
This results in greater accuracy. 
Both the Optical Interpolation System and the Electronic Contour-liner can be used on the GZ-1 Orthoprojec- 
tor in the off-line mode. In addition to the well-known advantages of the off-line mode (optimized use of the 
instrument, economical operation, efficient map revision, etc.), the new accessories will cut considerably the 
time and costs required per map sheet by reducing the running time in the Orthoprojector due to wider width 
of the strip and by doing away with the need to construct contour lines. 
23. Hofmann, O. 
Germany (F.R.G.) 
A NEW PHOTOGRAMMETRIC PLOTTING SYSTEM 
A new photogrammetric plotting system for graphical and digital plotting of stereopairs is described. 
A single basic outfit in conjunction with a number of accessories will cover the entire range of stereophoto- 
grammetric plotting encountered in practical work. 
The modular construction of this equipment system permits digital and graphical plotting of satellite pictures, 
air photos and terrestrial photography up to 9" x 9" and taken with focal lengths in the range from 50 mm to 
3276 mm. 
Contour lines 
planimetric maps, 
orthophoto maps and 
spacial coordinates 
are produced and measured at any scale. 
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