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:
