INTRODUCTION 
In recent years, there has been a growing interest in the possibilities of 
applying photogrammetric techniques to objects in the underwater 
environment. Early work has concentrated on underwater mapping of the sea 
bed, identification and mapping of shipwrecks and the measurement of 
marine biological specimens: (Pollio 1969, 1971; Rosencratz, 1971; 
Torlegard and Lundalv, 1974). 
More recently the growth of the offshore oil and gas industry has produced 
new applications. For the first time, large man made structures have been 
positioned and operated within the hostile and dynamic environment of the 
sea. These installations require a regular inspection and maintenance 
programme to ensure safety of operation. Several systems have evolved to 
meet the demand for underwater inspection and essentially these are based 
on the use of divers, manned submersibles or remotely controlled vehicles 
(rcv's). All systems employ underwater video and still photographic 
cameras but, at present, much of the interpretation of these visual records 
is only of a qualitative nature. Detailed visual inspection plays a large 
part in all current inspection systems. 
The suggestion that photogrammetry could also be used to monitor and assess 
damage of offshore installations appears to have originated with Pollio 
(1969) and was later re-iterated by Rebikoff (1976). However it was not 
until 1977 that the first large underwater photogrammetric damage 
assessment survey was carried out during the repair of the North Sea 
Heather platform leg (Welsh et al, 1980). Photogrammetric techniques were 
used to obtain accurate measurements of the size and shape of a damaged 
area of the platform leg so that a sleeve could be produced to match the 
buckling and cover the damaged surface. Gres (1980) has, also, reported 
on the use of photogrammetry in connection with the inspection of the base 
connector plate of the Frigg flare Structure. 
These applications demonstrate that photogrammetry has the potential to 
provide an efficient and accurate method for determining the size and shape 
of underwater objects and features and they have stimulated a great deal of 
interest both in the offshore oil industry and in photogrammetric circles. 
As a result it is likely that, before long, photogrammetry will be added 
to the range of non-destructive testing techniques available to the 
underwater surveyor. 
This paper discusses work to date on a project being carried out in the 
Department of Surveying, University of Newcastle upon Tyne in conjunction 
with British Oceanics Limited, an offshore underwater inspection company 
and currently the major operator of manned submersibles in the North Sea. 
The immediate aim of the project is to design and implement an offshore 
based photogrammetric measurement and analysis system adopting a manned 
submersible camera platform and using commercially available equipment. 
The emphasis is on achieving the minimum interference with general 
submersible operations, and producing results as quickly as possible to 
a consistent and acceptable level of accuracy. 
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