Simrad GC80 Instruction Manual download pdf (Page 24)

Simrad GC80/GC85 Compact Gyro Compass

16 20221511 / C

Speed

The GC80/GC85 gyro compass calculates bearing based on the

speed and latitude information that is input to the gyro system.

Any errors in speed input will therefore cause incorrect true

bearing from the gyro compass.

Press the DISP button until the vessel’s speed information is

displayed.

Confirm in 4 hours intervals that the displayed speed is the same

as the vessel’s actual speed.

Any discrepancy between displayed speed and actual speed is

corrected as described in Setting the Speed input system, page

51.

Speed error correction

Any gyro compass will generate a heading error caused by

vessel speed and the earth rotation. GC80/GC85 calculates this

error based on latitude and speed input information, and corrects

automatically the bearing signal output. If no speed information

is available, the gyro compass will output a heading error either

westwards or eastwards depending on the vessel’s course.

If speed information is unavailable, the figure on next page

could be used for manually calculating the heading error.

In this figure, the following values are used as example:

- Latitude: 40°

- Vessel speed: 16 knots

- Vessel heading: 30°

The heading error is found by:

1 Drawing a line between the latitude and the vessel heading

(shown with gray line on the figure)

2 Drawing a straight line (broken line in the figure) between

the vessel speed and the point where the latitude/heading

line intersects with the solid black line in the figure.

In the example above, the figure shows a speed error of appr.

1.1°, and the true bearing should then be 30°-1.1° = 28.9°.

Note! When the course is within 270° - 0° - 90°, true heading is found

by subtracting the speed error from the compass heading.

If the course is within 90° - 180° - 270°, true heading is found

by adding the speed error to compass heading.

1 2 ... 19 20 21 22 23 24 25 26 27 28 29 ... 111 112

No comments

Simrad GC80 Instruction Manual Page 24