Until the summer of 1994 we had measured the track with two inclinometers
of 1" resolution made by British Aerospace. These were alternately mounted
on the A-frames and the TMU and measures taken each 1-degree of azimuth.
Various problems outlined below (see Sect.5 Data Acquisition and
Strategies) necessitated repeated measurement at regular
intervals that forced much slewing of the antenna back and forth.
This modus operandus had several drawbacks, not least the protracted
length of time required to obtain the necessary data with which to construct the
track model. In addition, obtaining enough data to provide checks on
repeatability and other characteristics doubled and re-doubled the time
required.
A new system was needed to ensure that inclinometry data could be taken
much more rapidly and repeatably, thus avoiding many problems associated with
the old system. Such a system would include