TM 5-6675-250-20
2-16. DETERMINATION OF AZIMUTH VALUE FOR REFERENCE MIRROR (Continued)
L O C A T I O N / l T EM
A C T I ON
R E M A R KS
SERVICE (Continued)
N O TE
Actuation of the RESET switch reinstates the servo mechanism so that it
m a y c o n t i n u e t o t r a c k a n d d a m p t h e p e n d u l u m f o r a m i n i m u m o f 45
seconds. Under normal operating conditions, it is not required to use the
reset, for it would only delay the azimuth determination with little improve-
ment in azimuth determination accuracy. Three possible examples of when
to use the reset are: (1) an abnormally short alignment time, (2) when the
GRU or tripod has been disturbed after the READ AZIMUTH indicator illumi-
nates, or (3) after an immediate full scale deflection in either direction on
the TEST METER FOLLOWING ILLUMINATION OF the READ AZIMUTH in-
dicator. Considering time available to establish azimuth and accuracy re-
quired, the operator must exercise judgment prior to performing the reset
operation. In order to avoid error accumulation, it is recommended that the
RESET not be used later than 20 minutes after biasing.
x.
Read and record the azimuth to
the target and the reference mirror angle, us-
ing both direct and reverse readings.
y.
Repeat step (x) for the counter-clockwise turn
d i r e c t i o n .
z.
Repeat steps (x) and (y) for a total of ten
a z i m u t h d e t e r m i n a t i o n s .
a a.
Calculate the arithmetic mean of the deter-
mined azimuths and subtract from the known
value.
a b.
Calculate the arithmetic mean of the
measured reference mirror angle and
algebraically add to the resultant of step (aa).
The result of this calculation is the new refer-
ence mirror azimuth value.
2-82
