Digital Photogrammetric Applications 
with the 
Prime-Wild S9 Analytical Plotter 
David Wilkins 
Institute of Geodesy and Photogrammetry 
Swiss Federal Institute of Technology 
ETH - Hönggerberg 
CH - 8093 Zürich 
Switzerland 
Abstract 
In the context of a collaborative project currently underway at the Institute of Geodesy and 
Photogrammetry of the Swiss Federal Institute of Technology (ETH) in Zürich, a Prime-Wild 
System-9 Analytical Plotter (S9AP) has been modified to enable the installation of a pair of CCD 
cameras. Together with appropriate image acquisition hardware and host computer, the S9AP is 
thus transformed into a general-purpose image scanner for digital photogrammetric applications. 
Before the instrument can be used as such, it is necessary to perform a calibration to determine the 
relationship between the digital image pixel coordinate systems and the S9AP stage coordinate 
systems. An extensive software package has been written for this, which contains some special 
components made necessary by the mechanical design of the instrument. As a means to 
demonstrate the potential accuracy of the system, the signalised points of a photogrammetric test 
block were digitised, their coordinates determined by template matching and subsequently 
processed in a bundle adjustment. The results of this investigation are presented, together with a 
comparison with the results from a manual measurement of the same block on the same instrument. 
Key words: analytical plotter, digital photogrammetry, image matching, bundle adjustment. 
1. Background 
The aims of this paper are twofold. It arises out of 
the work done over the last two years on a 
collaborative project between the Institute of 
Geodesy and Photogrammetry of the Swiss Federal 
Institute of Technology (ETH) in Zürich and Wild 
Heerbrugg. The purpose of the project was to 
develop a system for automatic DTM data 
generation through image matching, using the 
analytical plotter System-9 AP (S9AP) as an on 
line source for analogue image information. To 
this end, an S9AP with an adaptation to its optics 
allowing the attachment of a pair of CCD cameras 
was installed in Zürich. The work on the project 
then followed two major paths: calibration of the 
hardware and algorithms for the image matching. 
The first aim of this paper is to present the result of 
the former, that is, to introduce the modified S9AP 
as a general-purpose image scanner. 
The second aim is to present one possible 
application using such a system - aerial 
triangulation using image coordinates determined 
by point location in digital images. This lies 
outside of the specific aims of the project, but it has 
always been seen that the modified S9AP could 
have applications in other areas; the overall aim is 
to show this. 
The paper is organised into two parts reflecting 
these dual aims. The first part (sections 2 and 3) 
will describe the system hardware, the procedures 
for its calibration, and some results therefrom. The 
second part (section 4) will concentrate on the 
aerial triangulation investigation - the data 
acquisition and the results of bundle adjustments 
thereon. 
2. Hardware Introduction - the S9AP 
2.1 Analytical Plotters as Image Scanners 
Since analytical plotters became generally accepted 
in the commercial sector in the early 1980’s, there 
have been various attempts at installing them with 
CCD cameras to enable the digitisation of image 
sub-scenes. In the most cases, the subsequent 
processing of the digital imagery was aimed at, but 
not restricted to, the automatic or semi-automatic 
generation of height data for DTM applications. 
Two of the major photogrammetric instrument 
manufacturers ran projects along these lines. Zeiss 
Oberkochen of West Germany, in collaboration