Methods For Finding Gyrocompass Error
There are three celestial methods used by QMs for finding gyrocompass
error. They are:
Azimuth of the Sun
Azimuth of Polaris
Amplitude of the Sun
In each case, you are required to gather data for use in computation.
This data may be in the form of sights from the sextant, time in GMT,
DR Lat. and Long., and so forth. For each celestial method, we will
begin with gathering the necessary data and then working the solutions.
Azimuth of the
You must know the following values to determine gyrocompass errror
Time of the actual observation
Date of the observation
DR position at the time of observation
Azimuth (gyro bearing of the Sun)
Rule: Due to the elevation of the Sun, azimuths should be taken in
mid-morning or mid-afternoon.
Use the following table to gather the data to work the azimuth solution.
You must have a recorder present to mark and record the exact time of
Obtain a time tick from WRN-6 or chronometer with a
Break out and place the azimuth circle on the gyro repeater
closest to the Sun.
Align the Sun in the reflecting mirror in a manner so that the
rays reflect back through the prism housing and onto the
When each spirit level is leveled, mark the time and record the
reflected gyro bearing from the compass card to the nearest
0.1°. Note: This is a difficult procedure in heavy seas;
however, if the azimuth circle is not level, errors will occur.
Repeat steps 4 and 5 a minimum of three times.