Raymarine C120, Installation Manual

Page: 44 / 54

38 C-Series Displays Installation Manual
Radar alignment checks
You should check the bearing and display timing alignment to ensure that an accurate
picture is shown.
Bearing alignment
Adjusting the bearing alignment ensures that targets appear at the correct bearing
relative to your boat’s bow. You need to select a visible target of known bearing that is
displayed on the radar, and then adjust the radar set up as necessary until the correct
bearing reading is obtained.
You can carry out a bearing alignment in two ways:
... with your boat moored
To use this method you will need a hand bearing compass:
1. Visually identify a suitable target, such as a buoy that can be seen towards the edge
of the radar screen. Typically, this will be on the 1.5nm range.
2. Determine the accurate bearing of the target relative to your boat’s bow using the
hand bearing compass. To do this subtract your boat head bearing from the target
visual bearing, these examples may help:
3. From the primary radar soft keys, press VRM/EBL.
4. Toggle the VRM/EBL soft key to ON. Adjust the EBL to your chosen target. If there is
a difference between your calculated bearing and that shown for the EBL, there is
an alignment error and you will need to carry out bearing alignment adjustment,
See “Adjusting the bearing alignment” on page 39.
... with your boat under way
1. Align your boat’s bow with the selected target.
2. Note the position of the target relative to the Ships Heading Marker (SHM) on the
radar picture. If the target is not under the SHM, there is an alignment error and you
will need to carry out bearing alignment adjustment. For details see below
.
Example 1 Example 2
Visual bearing (a) = 065° M Visual bearing (a) = 030° M
Ships head bearing (b) = 021° M Ships head bearing (b) = 042° M
Relative bearing:
= (a) - (b)
= 065 - 021 = 044° R
Relative bearing:
= (a) - (b)
= 030 - 042 = -012
If answer is negative, add 360° =
-012 + 360 = 348° R
87020-3.book Page 38 Tuesday, March 7, 2006 11:02 AM