TM 5-6675-250-20
2 - 1 0 . T R O U B L E S H O O T I N G ( C o n t i n u e d)
T a b l e 2 - 3 . T r o u b l e s h o o t i n g ( C o n t i n u e d )
M A L F U N C T I O N
TEST OR INSPECTION
CORRECTIVE ACTION
GYROSCOPIC REFERENCE UNIT (GRU) (Continued)
6 . I N A C C U R A T E T H E O D O L I T E R E A D I N G I N D I C A T I O N S .
Step 1.
Check reference mirror for improper alignment.
a. Set-up the SIAGL with the GRU over a base line of a known azimuth.
b . P e r f o r m o n e a z i m u t h d e t e r m i n a t i o n .
c. Set the theodolite horizontal circle to the azimuth of the known line,
with the theodolite on target.
d. Place the MODE SELECT switch (1) on the ECU (2) to SELF TEST (3)
and the TEST SELECT switch (4) to CW (5), and turn the GRU output
shaft 5 to 10 degrees clockwise from the position of the previous
azimuth determination. Switch the SELF TEST switch (3) out of the SER-
VO position (6) to stop the turning action.
e . P e r f o r m a n a d d i t i o n a l a z i m u t h d e t e r m i n a t i o n.
f. Read and record the azimuth to the target and the reference mirror
angle, using both direct and reverse readings.
g. Repeat step f for the counterclockwise turn direction.
h. Repeat steps f and g for a total of ten azimuth determinations.
i. Calculate the arithmetic mean of the determined azimuths and sub-
tract from the known value .
j. Calculate the arithmetic mean of the measured reference mirror
angle and algebraically add to the resultant of step (i). The result of this
calculation is the new reference mirror azimuth value.
2-29
