Observations were taken on approximately fifty days over a
two-and-a-half month period, with roughly 60% of the observa
tions having been taken at University Pillar. Over nine hundred
"reversal points" and "transits" were observed, the tracking and
the transit methods each providing roughly twenty-five deter
minations of gyro-indicated north. The "breakdown of observations
and determinations is shown in Table I below. Table II shows the
comparison of the gyro-indicated norths' differences obtained at
the ends of the test line with meridian convergence.
24
In the foregoing Table II, each of the sixteen determinations of GIN
at University Pillar has been compared with each of the eleven
determinations of GIN at Waterval, by the tracking method, and
the average and highest positive and negative discrepancies re
corded. Identical comparisons are also recorded for the determi
nations of y by the transit method. No special considerations have
been given to weighting of individual gyro-indicated north deter
minations, in the comparisons with y, as precision does not appear
to be solely a function of the number of observations taken. There
does, however, appear to be some relationship between the number
of times the secondary harmonic (SHAR) effect is successfully
captured and relative precision, even although the set of obser-
278
Table I Breakdown of Observations
Method
Total No.
No. of
T.P.'s
No. of Independent
Observation Sets
Total
of Obs.
Transits
For Back
Tracking
679
8
16
20
3°
45
3 3
4 2
2 0
3 3
4 3
27
Transit
230
5
10
20
6 4
6 4
3 1
24
Table II Discrepancies between Gyro-indicated Norths
v (seconds of arc)
Method
Mean
Maximum
Positive Negative
Tracking
8
20
Transit
9
26
22
