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Azimuth of the Sun, Continued
Tab Z
Exact Z (-360)
Exact Zn
Drop the value from Tab Z.
Apply the Total Corr to Tab Z (- 0.10).
On each page of Pub 229 are small notes that
state:
129.1
129.0
231.0
In N. Lat. if LHA is Greater than 180 then Zn= Z
if LHA is Less than 180 then Zn= 360-Z
In S. Lat. if LHA is Greater than 180 then Zn= 180-Z
if LHA is Less than 180 then Zn= 180+Z
Gyro Bearing
Gyro Error
Our Lat is N. and LHA is less than 180,
therefore Zn=360 - 129 or 231°.
Enter the gyro bearing from the observation.
Find the difference between Exact Zn and the
gyro bearing and name the error. If the gyro
bearing is less than the Exact Zn, the error is
easterly, if more than Exact Zn, it’s westerly.
Use this memory aid:
231.6
0.6 West
Gyro least - error east, Gyro best - error west.
We have now used the Sun to find the error on our gyrocompass. As stated
before, a greater degree of accuracy can be obtained by making several
observations and then working the solutions and averaging the results. This
may seem a bit tedious, however, you may work all observations at once.
This is easily accomplished by entering data in the strip form in stages.
Try this method. First enter GMT DR Lat, DR Long, GHA, Dec, and d#.
Next find Incements (m/s), LHA, and True Dec. Now find your leftover
values for Dee Inc, Lat Inc, and LHA Inc and enter Pub 229.
Once you have completed the solutions for all obsvervations, you can average
the results. Here’s an example:
Error 1 = .6 W Error 2 = .5 W Error 3 = .7 W for a total of 1.8 ÷ 3 = .6 W
9-10
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