PROGRESS AND POTENTIAL OF DIGITAL PHOTOGRAMMETRIC 
WORKSTATIONS 
IAN DOWMAN 
University College London 
Gower Street 
London WC1E6BT 
Abstract 
This paper reviews the development of digital stereoscopic photogrammetric workstations and 
looks at their potential use in the next few years. A joint workshop of ISPRS IWG II/III and WG 
V/4 held in february 1990 discussed the application of fast processing to workstations, the 
findings of the workshop are reviewed and compared to the realisation of systems. The use of 
transputers and other fast processing hardware is essential for the efficient development of 
photogrammetric workstations and particuar attention is paid the these components. 
Introduction 
There has been a considerable interest in the use of digital data in the past few years which has led 
to a significant increase in the speed of development of digital workstations. Prior to 1988 there 
had been a number of systems discussed in the literature but these were either prototypes or for 
specialist applications. At the ISPRS Congress in Kyoto in 1988 two commercial systems were on 
display in the exhibition and a number more were discussed in the technical sessions. In addition a 
number of workers reported the use of standard general purpose workstations for stereo 
measurement and there was great interest in components and software which would aid this 
development. Since 1988 the rapid increase in the speed of computer systems has continued and 
today a number of possibilities exist. 
Developments in both hardware and software were reviewed at a joint workshop meeting of 
ISPRS IWG П/Ш and WG V/4 on the application of fast processing to workstations, held at 
University College London in February 1990. The papers and discussion at this meeting give an 
up to date view of the the state of development and will be reported in this paper. 
Definition and role of a digital photogrammetric workstation (DPW) 
A digital photogrammetric system is defined in the terms of reference of ISPRS IWG II/III as 
"hardware and software to derive photogrammetric products from digital imagery". This clearly 
embraces close range, aerial and satellite imagery and also co-ordinate determination, line maps and 
digital elevation models (DEM). The key elements relating to photogrammetry are digital imagery 
and co-ordinate determination; other aspects such as identification of features and automated 
functions are less important to the concept of a digital photogrammetric workstation. 
The question must be asked: why are digital photogrammetric workstations needed? Are they 
developed just because the technology is there? Without a good digitiser aerial photographs cannot 
be used in a digital system. DPWs are however needed to handle data originally recorded in digital 
form, and one of the main reasons for developing photogrammetric workstations is to allow 
human intervention in automatic processes; the objective for such systems must be to eliminate the 
human operator altogether but such an aim will not be achieved for some years to come. The 
development of automatic techniques is therefore very much tied up with that of workstations. The 
computer power needed for manipulating the data is also needed to carry out automatic 
computations. 
A photogrammetric workstation should be seen as a window into the data base whereby the 
operator can interact with the data and with the functions performed on it. In a photogrammetric 
context this implies stereoscopic viewing and real time scanning of the data. The features which 
specifically characterise a photogrammetric workstation can be defined as: