OBSERVATIONS WITH PIM

Abstract

The performance of gyro-theodolites is not widely known amongst land surveyors because the use of these costly instruments is mainly confined to mining and artillery surveyors. The instruments themselves have been well described: accounts of the pendulous type in which the spinner hangs by means of a thin filament aligned in the vertical axis of the theodolite are given by Strasser & Schwendener [1] and Schwendener & Ward [2]; whilst the floated rate-integrating gyroscope manufactured by the British Aircraft Corporation and known as the Precision Indicator of the Meridian, or PIM for short, is the subject of lucid papers by Sutton & Thomas [3] and Thomas [4, 5]. The results of PIM observations taken under Thomas' direction are given in his papers, but the only protracted series quoted are those for the determination of azimuth inside the Sperry factory [5; p. 58] and these results are briefly summarized.