SUCCESSFUL DIGITAL PHOTOGRAMMETRY AT THE ORDNANCE SURVEY OF IRELAND 
; Richard A. Kirwan 
Director of Operations, Ordnance Survey, Ireland 
Scott B. Miller 
Director of Engineering, Helava Associates, Inc., USA 
A. Stewart Walker 
Product Manager Digital Photogrammetry, Leica AG, USA 
Commission IV, Working Group IV/4 
KEY WORDS: Digital Photogrammetric Systems, National Mapping Organization, Production, Scanner, 
DEM/DTM, Orthoimage, Feature Extraction, Automation. 
ABSTRACT 
Ordnance Survey continues its pioneering role as the world’s premier national mapping organisation in terms of the 
adoption of digital photogrammetry for daily production. The first two, well known phases have been supplemented by 
a third major procurement of workstations, accompanied by installation of a complex network to increase productivity. 
Special software has been added for quality control of digital orthophoto sheets. A fourth phase, which may include 
monoplotting from the orthophotos, is at the design stage. Not only is digital photogrammetry productive and 
successful in its natural roles of generating digital terrain models and image maps, but it is also equal to or better than 
analytical plotters for feature collection in terms of productivity and operator satisfaction. The Irish procurements have 
been facilitated by appropriate financing and the new technology has enabled Ordnance Survey to provide the vast 
amounts of timely information which the European Community's programmes have required. 
1. INTRODUCTION 
The Ordnance Survey of Ireland (OSI) is Ireland's 
national mapping, organisation, established in 1824 and 
headquartered in Dublin. A popular history is provided 
in Anon (1991). OSI's mandate to map Ireland and to 
create medium and large scale digital databases has 
necessitated formidable and complex investment in new 
technology since the 1970s. OSI expanded radically 
following a decision in 1968 to accelerate the updating of 
its considerable range of map sheets, some of which had 
been rather neglected since Ireland had become a free 
state in 1922. More recently, OSI has invested in modern 
technology for all aspects of its work, based on a digital 
mapping system supplied by SysScan (now Sysdeco), 
running largely on Digital computers interconnected by 
DECnet. A progress report was given by Walsh (1987). 
The increases in productivity have been salutary. As a 
result, mapping staff have been reduced in number to 
around 270, 65 of whom are in survey control and data 
acquisition, 140 in large scale digital compilation and 65 
in small scale compilation, map production and digital 
data distribution. OSI’s operations are to some extent 
decentralised: 170 of the above staff are in the Dublin 
headquarters and 100 in six regional offices. 
2.0 PHOTOGRAMMETRY AT OSI 
The modernisation programme has included major 
investments in photogrammetry, necessitated by the 
extensive requirements. 
2.1 OSI’s mandate 
The current programme is oriented to photogrammetric 
resurvey rather than labour intensive revision by field 
925 
methods. The tasks, ranked in order of priority, may be 
summarised as follows: 
() maintain the existing 1:1000 urban mapping in 
a structured digital database and resurvey by 
photogrammetry whenever updates are required 
(ii) establish and maintain a small scale, structured 
digital database from imagery, mainly aerial 
photography, capable of graphical output at 
scales from 1:10,000 to 1:500,000, giving a new 
1:50,000 series high priority 
(iii) establish and maintain a large scale, structured 
digital database by photogrammetric resurvey, 
capable of graphical output at scales from 1:500 
to 1:10,000 
(iv) participate in the commercial mapping business. 
2.2 Analytical photogrammetry 
The acquisition of 16 analytical plotters took place at 
much the same time as the implementation of the digital 
mapping system. A Kern DSR1 was installed in 1982 
and by 1992 there were 11 DSRs, 4 Zeiss P3s and a 
Leica SD2000; the complement of analogue instruments 
had been reduced to 4. An increasing number of the 
systems run KLT ATLAS software for map compilation, 
though Kern MAPS200, Zeiss PHOCUS and Leica PC- 
PC-PRO600 with Bentley Systems MicroStation are also 
in use. The analytical plotters were deployed almost 
entirely on the large and small scale databases before the 
digital procurements. Triangulation was performed using 
natural control, pass and tie points on the DSRIs, 
adjusted with PAT-MR on a VAX minicomputer. In 
1993 a Barco publishing system was added, consisting of 
Barco workstations and Mercator map finishing 
software, an IRIS variable inkjet plotter for proofing and 
a Barco MegaSetter laser plotter, to enable the 1:50,000 
sheets to be published in the latest manner. The large 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996