The Photogrammetric Society Analogue Instrument Project: An Eighth Extract

Abstract

This eighth and penultimate extract from the Archive is an unusual one for a number of reasons. Of these the most important one is the fact that it is concerned solely with instruments produced in Great Britain. It is therefore concerned mainly with the Thompson‐Watts plotter, the only British instrument to go into full‐scale commercial production. Strictly speaking the other instrument included in this extract should not have had a separate entry at all, simply because no instrument of this type exists now and so cannot have an entry in the catalogue of instruments. However, in order to trace the development of the Thompson‐Watts Mk 2 plotter, produced in 1963, from the remarkable work of Henry Fourcade carried out in the 1920s, the Barr and Stroud ZA2 plotter based on his work has been accorded an Appendix of its own.Both instruments in this extract are based on an optical‐mechanical solution to the photogrammetric problem of space intersection and the Thompson‐Watts is in fact the only instrument of this type to be found in the catalogue. This particular solution did not find great favour on the continent and so few instruments of this type were produced commercially.