A silly question: Do I need a radar?

[gjgm]

Good day, guys,

Thank you very much for all the inputs.

I am based in north Taiwan, and my main boating area is north-east of Taiwan, roughly
between Taiwan and Okinawa (Japan). My boat is about 28'. (Not arrive yet.)

In this area, fog is not a big problem but this is a busy area, all kind of boats, cargo ships,
vessels ... These are my main concern. We all know that big ships don't go around the small
ones.

You could start with an AIS receiver if it is big boats that concern you ..it should plug into your plotter and then you can see what is about and get an alarm if there is a potential danger and the direction it is coming from. Personally it is the direction info that I really like, even in good weather-you know where to be looking. Sure, it doesn't necessarily cover all boats but I am more apprehensive about a few hundred thousand tons coming at me at 20 knots than a 35ft sailing boat at 3 knots. If you feel this is not giving you the added security you want, you could look into radar, but for localised day boating it might well be adequate.

 

[NBs]

I use my radar all the time when steering from the lower helm. For me its a second pair of eyes particularly when there's a lot of spray around and the MARPA facility is very useful for ascertaining whether you are in a potential collision situation with another vessel. One thing I would definitely not do is buy one and then not use it until you really need it because it takes a bit of practice to learn how to use it. That practice is best done on fine calm days when you can play with it whilst not under pressure and then the one time you really need it, you can use it without panicking

Hi,

Hi, I wonder if your marpa works well or perfectly or not?

I have a third raymar radar, currently digital 4kw, i get the boat taken for the target but the vectors usually look quite crazy sometimes the same speeds seem flawless even with time autopilots and the same target. I also have a crew ship and experience pro radar and they marpa work fine.

I can not rely on my raymarin marpa and possible collision forecasts. How are you marpa working?

NBs

 

[Deleted User YDKXO]

Hi, I wonder if your marpa works well or perfectly or not?

The short answer is that nothing ever works perfectly on a boat but you are right to raise this question because Marpa is not an exact technology especially on small boat radars. The radar has to determine the range, heading and speed of other targets as well as comparing that to your heading and speed which, of course since you are in a small boat, may be varying considerably. And yes if you look at the Marpa info on the screen it will vary often quite wildly, especially the speed of other targets. However as I said the radar is a second pair of eyes and eyes are fallible. If you detect a Marpa target on the radar dont just believe the first information you see on the screen. Keep watching how the info changes and if, on average, it is predicting a CPA (closest point of approach) that is uncomfortably close then prepare to take action. Its like anything on a boat. You have to compute information from all sources, not just from one source, before making a considered decision and Marpa is just one of a number of sources of information

 

[jfm]

Hi,

Hi, I wonder if your marpa works well or perfectly or not?

I have a third raymar radar, currently digital 4kw, i get the boat taken for the target but the vectors usually look quite crazy sometimes the same speeds seem flawless even with time autopilots and the same target. I also have a crew ship and experience pro radar and they marpa work fine.

I can not rely on my raymarin marpa and possible collision forecasts. How are you marpa working?

NBs

Remember, a radar is excellent at measuring the distance of a target, but much less good at measuring its heading. It relies on knowing your boat's heading for starters, as well as on the angle of what it measures, so that's 2 additive sources of error.

To get decent heading info you need a fast heading sensor and quality scanner gear.

Assuming you have imperfect heading data, your marpa results will be more random for boats crossing ahead of you than boats coming towards you or going in same direction as you. Keep that in mind as you interpret results. In any case, marpa will rarely be wrong about someone coming towards you (approach speed 40 kts?) versus going away from you (approach speed 3 knots?)

You just gotta interpret the data in light of the system weaknesses, and not expect it to be right. If you overlay AIS on your radar screen you'll build up knowledge of circumstances when your Marpa is likely to be bad/good.

All that said, mine works quite well and not as bad as you describe!

 

[NBs]

The short answer is that nothing ever works perfectly on a boat but you are right to raise this question because Marpa is not an exact technology especially on small boat radars. The radar has to determine the range, heading and speed of other targets as well as comparing that to your heading and speed which, of course since you are in a small boat, may be varying considerably. And yes if you look at the Marpa info on the screen it will vary often quite wildly, especially the speed of other targets. However as I said the radar is a second pair of eyes and eyes are fallible. If you detect a Marpa target on the radar dont just believe the first information you see on the screen. Keep watching how the info changes and if, on average, it is predicting a CPA (closest point of approach) that is uncomfortably close then prepare to take action. Its like anything on a boat. You have to compute information from all sources, not just from one source, before making a considered decision and Marpa is just one of a number of sources of information

Hi,

Thanks for your response, I used to talk quite outspoken, even though it is always an advantage. I give praise only if I am 100% behind what I'm saying, it is a boat, accessory, or any, I hope it will not offend anyone. I appreciate your response and I believe that we see the gaps in the enjoyment of the boat radar. I can count on my radar to picture 100%, but marpa and any other computational information associated with marpa, unfortunately great suspicion, but know this, it is great help in addition to your own eyes or if you can not see I can rely on radar echoes and years of experience. Digital radar is also a great improvement vs previous precision display and segregation of items. I hope others better, but I recommend using them all the time and learn what they can tell you when it comes to the moment that you really are on electronics, for example, a thick fog or real darknes.

My Raymarin aisi, I think it's a joke which cost € lot and I'm happy if it works in other ...

Nbs

 

[NBs]

Remember, a radar is excellent at measuring the distance of a target, but much less good at measuring its heading. It relies on knowing your boat's heading for starters, as well as on the angle of what it measures, so that's 2 additive sources of error.

To get decent heading info you need a fast heading sensor and quality scanner gear.

Assuming you have imperfect heading data, your marpa results will be more random for boats crossing ahead of you than boats coming towards you or going in same direction as you. Keep that in mind as you interpret results. In any case, marpa will rarely be wrong about someone coming towards you (approach speed 40 kts?) versus going away from you (approach speed 3 knots?)

You just gotta interpret the data in light of the system weaknesses, and not expect it to be right. If you overlay AIS on your radar screen you'll build up knowledge of circumstances when your Marpa is likely to be bad/good.

All that said, mine works quite well and not as bad as you describe!

Hi,

I understand what you think, but I see things more clearly by looking at the radar's basic evidence. If I use my raymar marpa items moving on the screen logically, but the target vectors often look like the way the hell, forgive my rough expression or the wrong description of that vector directions can not be trusted. I hope that other marpa data would be useful when doing navigation analyzes.

NBs

 

[jfm]

Hi,

I understand what you think, but I see things more clearly by looking at the radar's basic evidence. If I use my raymar marpa items moving on the screen logically, but the target vectors often look like the way the hell, forgive my rough expression or the wrong description of that vector directions can not be trusted. I hope that other marpa data would be useful when doing navigation analyzes.

NBs

The vector will be erroneous as to both speed and direction of the other vessel but if you let it gather data for 5mins it will be perfectly able to distinguish between a boat broadly coming towards you and one broadly going in same-ish direction as you. That's useful. The data will be better if you have 10hz gps not 1hz, a fast fluxgate unit and a 48/72 inch open scanner rather than 18inch radome.

 

[Hurricane]

We used to use MARPA a lot but these days, we tend to use the AIS CPA facilities which are much more accurate.
And the only use MARPA for those targets without AIS.

Here is an example

However, we do use the radar as well

There is another good use for radar - weather.
In the Med, rain is my biggest enemy/concern.
It creates local strong unpredicted wind.
In the pic below I was able to stow the bimini before hitting apparent winds in excess of 45 knots.

 

[MapisM]

In the pic below I was able to stow the bimini before hitting apparent winds in excess of 45 knots.

You mean the large area of rain south of your position, on your stbd side, I suppose.
It's impressive how clearly it stands out, but I'm even more impressed by how accurate the overlap with the chart is - particularly above Punta Sa Beca.
I can't remember, what model of Raymarine scanner/radome have you got, exactly?

 

[Zing]

Hi,

I understand what you think, but I see things more clearly by looking at the radar's basic evidence. If I use my raymar marpa items moving on the screen logically, but the target vectors often look like the way the hell, forgive my rough expression or the wrong description of that vector directions can not be trusted. I hope that other marpa data would be useful when doing navigation analyzes.

NBs

MARPA with a digital Raymarine radar should work fine regardless of scanner type if you are tracking a decent target. The most likely reason for dissatisfaction will be duff data from a heading sensor, properly located and set up. You would be best served with a good one such as an Airmar or Maretron.

 

[peterjaw]

There is another good use for radar - weather.
In the Med, rain is my biggest enemy/concern.
It creates local strong unpredicted wind.
In the pic below I was able to stow the bimini before hitting apparent winds in excess of 45 knots.

We have exactly the same problem in Taiwan, too. In summer, afternoon thunder shower is almost daily. The thunder shower just
come-and-go, usually last no more than 2 hours. Strong wind always comes prior to the heavy rain, sometimes it can be F6 or F7.

 

[Topic]

Just my opinion but collision avoidance is improved with radar. Set to 12m range, vessel targets show up well and bearing and range markers set on a target will with a little practice,tell you course and speed of the target and whether a collision risk is evident. Leaves more time for bridge watchkeeping and those pesky fishing buoys!

Also one day in thick fog down to 5 mtrs, left Salcombe from well up the harbour and navigated out on radar and chartplotter with no problems. Fog may not be often but you are snookered when it comes down without radar. As someone said earlier,if you can afford it, fit it and use it in good and bad visibility, until it is second nature.