Radar - automatic tracking devices

[RMA]

My boat is fitted with a Koden MDC-721 radar. It has proved invaluable at times, but I must confess it can be worrying tracking a number of targets at the same time. An ‘Automatic Tracking Aid’ is available as a bolt on option which claims to track up to ten targets at once and gives the alarm if any look as if they will be a problem. I’m tempted, but before I take the plunge has anyone any experience of it?

 

[Skyva_2]

That is MARPA - Mini Automatic Radar Plotting Aid. It does track 10 targets and monitors CPA and TCPA, and identifies dangerous situations. It works all right, but needs good heading input and consistent targets for consistency and reliability. Its probably not accurate to less than half a mile, and takes a few minutes to acquire course and speed when a target is selected.

If you have many targets it certainly eases the plotting load and most users will prefer it to manual plotting.

 

[homa]

Just to confirm what skysail has mentioned, you need a good heading input. I have just installed a s/h Raymarine MARPA set and they recommend on a good heading sensor - the one with rate gyro. These are not cheap, so do you homework on this before commiting to installing the plotter add-on to the radar.
Have seen the rate gyro s/h on e-bay from time to time.

 

[RMA]

Thanks for the replies. The radar will run with a north up display, getting the heading data from GPS. I haven’t used it much, preferring to use it in the head up display, but the plot does seem more stable when I do. Do you think the GPS heading data will be sufficient?

 

[Skyva_2]

North up display is stabilised/true motion, so the picture is more stable.

Leisure users normally use head up/relative motion for collision avoidance as it relates more easily to what you would see from the cockpit. As your heading changes the display will react, particularly in heavy weather, hence the need for a fast compass input for MARPA.

Your GPS would input course, not heading. What does Koden advise?

 

[homa]

The GPS will not give you heading input. It will only give COG, not fast enough for MARPA.

The manufacturer will recommend heading (from compass) and water speed.

Anything less will give very poor or useless plots.

Input from GPS will be for position only.