DIGITAL PHOTOGRAMMETRIC WORKSTATIONS 1992-96 
A Stewart Walker 
Product Manager Digital Photogrammetry, Leica AG, USA 
Gordon Petrie 
Professor, Department of Geography & Topographic Science, University of Glasgow, Scotland 
Invited paper, Intercommission Working Group III 
KEY WORDS: Digital Photogrammetric Workstations, Softcopy, Systems, Hardware, Software, Automation, Status. 
ABSTRACT 
Digital photogrammetric workstations are on the point of superseding analytical plotters, following a vigorous expansion of their 
use during the period 1992-96. An aggressively competitive market-place has developed, in which several manufacturers offer 
systems which perform the basic digital photogrammetric tasks - orientation, digital terrain models (DTMs), orthophotos, feature 
extraction - and in some cases include interesting additional functionality. The hardware platforms, operation and functionality of 
these systems are all improving apace, while certain developments of the software represent radical innovations, especially 
automated triangulation, mosaics and semi-automated tools for feature extraction. Acclaim of this technical wizardry must be 
tempered with comment on customers’ applications and expectations. Intriguing too is the ongoing debate whether digital 
photogrammetry is evolutionary or revolutionary and to what extent the promise of digital photogrammetry has been fulfilled in 
terms of the use of automation. While DPWs have an assured future and their accession to the role of workhorse in 
photogrammetric production is imminent, their perceived technical pre-eminence is conditional upon greater automation leading 
to unarguable increases in productivity and operator comfort, coupled with users finding markets for the much wider range of 
deliverables which digital photogrammetry can generate vis a vis analogue or analytical. 
1. INTRODUCTION TO DIGITAL 
PHOTOGRAMMETRIC SYSTEMS 
By 1992 digital photogrammetric workstations (DPWs) had 
begun their migration from military applications into the 
commercial market-place. This had taken ten years. Four 
years later their status is equal to, perhaps greater than, the 
analytical plotter (AP). They have not quite superseded 
analytical plotters, but almost so. Yet a DPW is not an AP: it 
performs the functions of an AP, but many more tasks besides. 
Why then the frequent comparisons with APs? 
By adopting digital methods, photogrammetry accepted its 
third “paradigm” and the change from analytical to digital is 
proving shorter and sharper than from analogue to analytical 
some 15 to 20 years ago (Leberl, 1991, 1992a). The huge 
growth of the DPW literature is informative: before the 1992 
Congress there were overview papers offering analyses, 
taxonomies and predictions, for example by Dowman (1991a, 
1991b), Dowman et al. (1992) and Schenk and Toth (1992); 
and there were product descriptions by vendors, for example 
Helava (1991a), lifting the wraps off previously less well 
known military systems, Kaiser (1991) and Nolette et al. 
(1992). Overviews were given at the last Congress, for 
example by Leberl (1992b) and are still written, both more 
penetrating academic analyses, for example Leberl (1994) and 
Heipke (1995a), and lighter pieces designed to bring 
appreciation of the technology to wider audiences, for example 
Trinder and Donnelly (1996). Vendors, too, continue to write 
updates on their latest product lines, for example Dôrstel 
(1995), Miller and Walker (1995) and Gagnon et al. (1995). 
Users have found their pens in droves, spurred by a desire to 
explain how they have encompassed the new technology, for 
example Corbley (1995), Foley et al. (1993), Johansson et al. 
(1995), and Kirwan (1996). Some go further and compare 
systems, for example Baltsavias ef al. (1996) and Kolbl 
(1996). The whole field has been surveyed by Heipke (1995b). 
Here we set DPWs within the overall digital photogrammetric 
process, then discuss the hardware and software, attempting to 
384 
discern trends where appropriate. We briefly compare DPWs 
and APs from the user's standpoint and assess how great an 
achievement the current status of DPWs may be. 
1.1 Basic components 
Digital photogrammetric systems have become well 
understood. The major characteristics are: 
(i) the system combines computer hardware and 
software to allow photogrammetric operations to be 
carried out on digital image data; 
(ii) the sets of digital image data consist of arrays of 
picture elements (pixels) of fixed size and shape; 
each pixel has one or more brightness values giving 
the value(s) of the radiance from the object field 
falling on each individual element of the imaging 
sensor; 
(iii) the sensor may produce digital data, for example a 
digital camera incorporating an areal array of CCDs, 
or a pushbroom scanner with a linear array of CCDs; 
(iv) data is often derived from a camera producing frame 
images on photographic film; these are converted 
into digital form using high precision scanners; 
(v) the main element of the system is the DPW on which 
the required mathematically based photogrammetric 
operations are carried out to produce data for input to 
digital mapping, CAD or GIS/LIS systems; 
(vi) these operations are performed manually or 
interactively, for example most feature extraction 
and editing, or using automated or semi-automated 
methods, for example DTMs and orthophotos; 
(vii) final output may take the form of vector line maps, 
DTM data files or image maps; thus many systems 
include raster plotters or film writers. 
1.2 Input data 
1.2.1 Sensors. The data volumes in digital photogrammetry 
are considerable, but vary according to the sensor. Digital 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996 
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