Conclusions 
In conclusion, it has been shown that for a relatively small cost, an 
existing analogue plotter can be digitised, and that its own drafting table 
can be used to provide an automated output, using for the most part widely 
available components and a standard microcomputer. This system is still at 
an experimental stage, but enough work has been done to show that it will 
work satisfactorily for production operation, with very considerable 
benefits in the speed and flexibility of recording and drawing cross- 
sections and other profiles. The system was designed to use as many 
'off the shelf! items as possible, and where parts had to be made specially, 
they were fabricated so that they could be fitted by the Unit's own staff, 
thus avoiding expensive site visits. 
The digitising of the plotter to record coordinates is a very straight- 
forward process. The conversion of the table to an electrical drive is 
perhaps more unusual. Clearly, utilisation of an existing coordinatograph 
in this way will not provide the sophistication and speed of operation 
of photogrammetric manufacturer's own automated flat-bed plotters. However 
for many small departments such as the Photogrammetric Unit, the cost of 
such equipment would be prohibitive, and it would also be under-utilised. 
Modification to existing equipment in this way, while having considerable 
limitations, does provide the opportunity to carry out more advanced tasks 
than would otherwise be possible. 
References 
Petrie G and Adam M O: The design and development of a software based 
photogrammetric digitising system. Photogrammetric Record, 10 (55): 
39 - 61 (April 1980) 
Hilger and Watts Ltd: Automatic Digital Recording, for the Thompson-Watts 
Mark II plotter. Leaflet CS170, (1964) 
Acknowledgements 
  
I wish to thank Professor Douglass Wise for his help and encouragement in 
preparing this paper. Also the Directorate of Ancient Monuments and 
Historic Buildings of the Department of the Environment, for permission to 
use material prepared on their behalf. For manufacturing parts and 
providing technical advice: Mr H F Ross, Mr L W Bateson, Digiplan Ltd, 
Soton Micro Systems and the University of York Electronics Department, in 
particular Mr Ross Kirk. Thanks also to the staff of the Photogrammetric 
Unit and my typist Mrs Jennie Tavener. 
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