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LATEST DEVELOPMENTS
RELATING TO
THE HILGER & WATTS STEREOCOMPARATOR
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Summary
The principle features of the Hilger & Watts Stereocomparator
are described together with the modifications and improvements
which have been introduced as a result of gaining user
experience. The advantages of the solid state decoding and
transmitting system are outlined, and the forms of recording
by punched card or teleprinter are given.
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The Hilger & Watts Stereocomparator was developed originally to
meet a War Office requirement for a measuring machine with automatic
recording of photo - co-ordinates and pre-set data. The prototype has
been fully described by A.H. Anstis (l), but since then a number of
changes have been ma.de to the production version. Though very little
alteration has been made to the specification or the principle of the
mechanical design the overall appearance has undergone quite a change,
and there has been considerable development in the recording system.
The first production model, which would, perhaps, be better des
cribed as a second prototype, was shown at the i960 I.S.P. Congress
Exhibition in London (still with a relay-operated recording system),
and described in a general review of stereocomparators by
I.A. Harley (2). All the development effort devoted to the project
between prototype and final production model has been directed towards
obtaining full user convenience, good mechanical functioning and accu
racy, and reliability in the digital recording system. Too much empha
sis, of course, cannot be placed upon the importance of the latter, and
the decoding and transmitting system now uses transistor switching
throughout, the advantages of which will be discussed later. For the
latter part of the development period the Ordnance Survey operated a
machine under test, and the assistance which they gave, both as an
organisation and as individuals, was of very great value indeed, and
has, in no small way, contributed to the successful development of the
final model. In this short account of the latest developments it is not
proposed to give a complete description of the machine, which has
already been done by Anstis and Harley, and may be obtained from Hilger
& Watts literature (3).
The fundamental specification was drawn up almost ten years ago,
by those with the foresight to see that reseaux photography offered
significant advantages for analytical photograrametry. We can now see
an increasing interest in the reseaux, Judging by the number of manu
facturers offering cameras with this facility.