273
The fallacy of using the consistency of consecutive Schuler
means as a criterion for acceptance of observations of the extremal
points of gyroscope oscillations, is illustrated by the following
twenty consecutive observations abstracted from a set of forty-five
observed on 13th May, 1966. A range of nearly one minute of arc
occurs in the Schuler means, the high-low pattern repeating
itself three times during the gyro-run. The full set of observations
took nearly three hours to complete.
Comparing the weighted mean of i8o°io'o6", derived from this
example, duly corrected by an orientation correction of +45", as
was applicable to the set, the instrument calibration constant would
be -f-10'51". This result compares to +5" with the calibration
constant of +io'4Ó" obtained from all observations. The accept
ance of the "high mean" would have resulted in an error of +44"
in the bearing of the line University Pillar Waterval. The
"middle mean" would have produced a fortuitous error of 1"
and the "low mean" would have caused a bearing error of 9".
It is of particular interest to note that it is virtually impossible
to make an advance decision concerning the number of observations
to be taken, if maximum accuracy is to be achieved, with the gyro-
theodolite. The location of the "high-low" range has to be found
before any set can be accepted as being complete. Of course, under
normal circumstances of application some practical upper and lower
Left
i790oi'56"
179.04.00
179.06.05
17g.08.40
179.11.16
179.11.5g
179.12.42
179.13.12
179.13.42
179.14.08
I79-I4-35
179.14.46
179.14.58
179.15.18
I79I5-39
179.15.49
I79-I5-59
179.16.09
179.16.19
i8i°I7'26"
181.15.12
181.12.59
181.10.21
181.07.43
181.07.18
181.06.52
181.06.25
181.05.58
181.05.24
181.04.50
181.04.41
181.04.32
181.04.14
181.03.56
181.03.48
181.03.39
181.03.20
181.03.02
Mean
i8o°io'43"
180.10.39
180.10.50
180.10.48
180.09.51
180.10.00
180.10.02
180.10.04
180.10.03
180.10.00
180.09.48
180.09.50
180.09.55
180.09.56
180.09.52
180.09.54
180.09.54
180.09.50
Remarks
High mean: i8o°io'45"
Middle mean: i8o°io'oo"
Low mean; i8o°og'52''
See note page 272.
