OR-1 LINKED WITH A PDP-11 MINICOMPUTER 
Grabmaier, K.A. 
ITC, The Netherlands 
Presented paper to WG II/1 
Abstract 
At the ITC a WILD OR-1 has been linked with a PDP-ll mini-computer 
instead of the NOVA computer which is usually delivered by WILD. 
The increased computational power and background memory permits an 
extension of the system capabilities. It is possible for example to 
produce orthophotos and stereomates directly from a DEM without the 
use of another computer. Moreover, the photo-coordinates of the 
ground control points needed for calculation of the transformation 
parameters, can be measured directly in the OR-l. "Facet-rectifica- 
tion" and "rectification of scanner images" by polynomials is also 
possible. 
This paper describes the present configuration and the existing 
programs and outlines the additional software to be developed. 
Further, the advantages of the described system in practical use are 
discussed and compared with the standard configuration (and the 
commercially available software). 
Introduction 
The first ITC concepts on digitally controlled off-line orthophoto 
printing date back to the beginning of 1969 [11. When the OR-1 was 
realised by Wild in 1976 its hardware was capable to implement most 
of the ITC's concepts, apart from the computer used for the process 
control. Its power was insufficient to carry out any additional 
tasks. Therefore the ITC purchased the optical-mechanical unit and 
the control electronics of the OR-1 and interfaced it, in close 
cooperation with WILD, to a PDP-ll minicomputer. 
At first a PDP-11/10 was used with one hard disk and one mag.tape 
unit. This configuration was quite adequate for the intended pur- 
pose, but for other, non-technical, reasons it was replaced by a 
PDP-11/45 with 2 hard disks and 2 mag.tape units and other periphe- 
rals. The software had to be developed fully by the ITC. The infor- 
mation needed on the hardware was supplied by WILD. 
The objective of this developement was to enable the system to pro- 
duce orthophotos and stereomates directly from terrain data. This 
terrain data could be either a limited number of irregularly distri- 
buted terrain points which describe the terrain by facets, or a 
regular grid DEM. With this approach it is not necessary to produce 
a different set of data for each product to be made. With the same 
input data set, an orthophoto or a stereomate can be made of a 
certain area, even from different photographs, at different scales 
or with different slits.