Using radar for collision avoidance is one of the most important reasons we have it installed.
Fog can be disorientating and dangerous and radar can be a great help if used properly
Using radar in head up mode allows you to track other vessels and check if risk of collision exists.
In this next step we will introduce a taget for you to track.
Time to have a look at dealing with rain.
The 'rain' control, also called FTC (fast time constant), suppresses the reflected echoes from rain, hail and snow on the display. Over suppression can reduce legitimate targets so use it with care.
The + button will increase the suppression and the - sign will decrease it.
Check the FTC percentage at the bottom of the screen. To start this needs to read zero.
The dangerous target is at the top right of the screen and to starboard of the vessel.
Place the EBL line on the target and decide if a risk of collision exists.
Should a risk of collision exist, the target is on your starboard side which makes you the give way vessel.
This would be a very poor decision. It would initially avoid a collision unless the target decided to take avoiding action and turn the correct way for collision avoidance which would be to starboard. You and the target would be back on a collision course with the target wondering what you were doing.
When altering course to take avoiding action it should always be to starboard if possible allowing vessels to pass port to port.
This is not the correct decision.
You are the give way vessel with a target approaching from starboard.
It is clear that the target is staying on the same relative bearing and that a strong risk of collision exists. Avoiding action should be taken early and be a large one to show the target a different aspect and make clear what your intentions are.
This is a mini radar simulator and only covers a few of the main features of an operational radar.
We recommend that all students take a RYA radar course before using this type of equipment on their vessels.
You can familiarise yourself with the controls before continuing. All active controls are stop/start.
First we need to remove the sea clutter usually caused by a big swell or breaking seas.
Use the Clutter +/- to reduce the clutter until it disappears but the target is still showing.
Over adjustment will result in losing sight of smaller targets. Around 90% should do it.
'HL' stands for heading line and is the line that depicts the vessel's heading.
For this lesson the heading line is set to 'head up' and the heading line displays the vessel's heading.
Use the on/off button to hide or show the heading line.
'RR' stands for range rings.
For this lesson the range rings are set at two miles apart and provide a quick way of estimating the distance of a target.
Click the RR on/off button to hide and show the rings.
The 'EBL' line or electronic bearing line is used to give a bearing relative to the ship's head and is useful to check if a risk of collision exists.
The EBL line should be rotated until it is centred on the approaching target. If the target stays on the line and gets closer to the centre, then a risk of collision exists.
Use the on/off button to toggle movement of the EBL line and the +/- buttons to rotate it.
The 'VRM' or variable range marker is used to find the distance of other vessels or objects on the display.
Used in conjunction with the EBL line the distance and relative bearing of a target can be found.
Use the VRM on/off button to hide or show the VRM and use the +/- buttons to adjust it.
Fair decision. But much better to slow right down and keep steerage way to maintain your aspect to the target. The target would pass ahead.
Pitfalls are that once you lose way your vessel will go off course, monitoring the target would become impossable as the aspect of your vessel changed and, if your vessel rotated, you could end up showing the target your port side causing the the skipper to take avoiding action.
Great decision.
A bold turn to starboard would keep you clear of the target and send a clear message that you had taken the correct decision and turned the correct way to avoid a collision.
Well done!
In this scenario a vessel is approaching from the port side.
Place the EBL line on it to see if it is on a collision course.
Select your decision.
Wrong decision.
The target it not on a collision course so should be monitored but you should maintain your course.
Correct the target is not on a collision course.
You should maintain a steady course and monitor the target incase it changes course.
Beam width.
The beam width of the radar may increase the size of a small target. Gaps such as harbour entrances can appear smaller on radar and when it is used for piloting a harbour entrance may only show when it is close enough for the radar beam to pass through the entrance. This is called bearing discrimination.
Radar Beacon shortened to Racon
When a racon receives a radar pulse, it responds with a signal on the same frequency putting an image on the radar display.
It is in the form of a short line of dots and dashes forming a Morse character radiating away from the location of the beacon. Using the VRM and EBL the bearing and distance can be obtained and used to provide an approximate fix.