NavList:

Byron,

On the subject of determining Gyro Error. The merchant ship's I've been on use various means to determine gyro error and other safeguards with regards to the gyro.

First and foremost, before the ship leaves the berth or enters into pilotage waters, the gyro repeaters, to include the helm, are all aligned to the master gyro compass. This is usually done with 2 officers via UHF radio. The radars, bridge wing repeaters, autopilot, and bridge repeater all all synchronized to the master.

Once the repeaters are synchronized, they are checked by various means. At a berth, the most common method used it to find the direction the ship is pointing via the chart and gryro error is determined in this way. I prefer the Franklin technique if the conditions exist, but if there is not a change in the normal gyro error, the former method is usually sufficient.

Once underway gyro error is again usually checked by ranges. Most channels have visual range markers and the gyro course can be checked against the charted range bearing when centered on the range. This is done as a matter of habit.

Once in the deep ocean gyro is checked by azimuth. In my standing orders, this is done once per watch (4 hours) as conditions permit and recorded both in the deck log and in the azimuth log. This allows me to see if the error is constant or is trending one direction or another.

I have been on only 2 ships in the last 7 years so I can't make sweeping statements on normal errors, but these ships typically between 0 and 0.5 degrees of gyro error at any one time.

As a note, most modern ships are using ring laser or flux gate compass instead of gyroscopes. My ships tend to be old, so I have no personal experience with this equipment.

I have used your techniques from anchorage in 2009 and found it highly effective. When next I sail, I will try it again and report my findings.

Jeremy
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