This is a first here at Attainable Adventure Cruising: Colin and John have teamed up on a chapter to share the fruits of some 70 years of combined radar experience, much of it in the foggiest (Atlantic Canada) and highest-traffic (English Channel) areas of the world.
[John’s thoughts begin and end with square brackets like this sentence, so you can keep the two of us straight.]
Let’s imagine that the fog has socked in good and proper. Radar comes into its own now, so:
A very nice list, especially as it covers the less-obvious traps of not varying ranges, being “speckle-phobic” and the potential for confusing orientations and the need for training. While I’ve played with a few older sets, I have to learn how to get the best from ARPA and how to integrate AIS into a stand-alone RADAR’s output. Well done, you two.
Thank you very much for a informative post..!
I very much agree with you guys regarding the radar overlay function on MFD´s. In my opinion I would say it’s more or less useless.
But when it comes to using split screen mode on a MFD on the other hand, I disagree with you.
I find it very useful to have radar and chart on a split screen mode. This way it will just take a split second to compare the radar picture and the map. Especially when operating in tight corners or unclean waters I really appreciate NOT having to switch modes or fiddle around with different buttons. One wrong button pushed, which easily happens in heavy seas, and you have to move focus from navigating into handling your MFD, and thats the least you want to do in such circumstances.
On our Furuno NN3D plotter the cursor on one screen show as a (red) cross on the other when in split screen mode, a tool I find VERY helpful. If I see a blip on the radar which I don’t recognize, moving the cursor over it, the cross corresponding with the cursor shows immediately where this blip is on the map. The other way around, place the cursor on lets say a buoy on the map, and you will se where the blip on the radar should show up.
One thing one must take into considerations using MFD´s with split screen mode, I think it ideally shouldn´t be of no less size than 9-10“.
Hi Marc
What we wanted to do was exactly that – cover the simpler stuff that often gets overlooked. ARPA is great and I like having AIS of radar a lot, too.
I’m sure I can speak for John, too, and say we’re glad you found this useful. Thanks for saying so.
Best wishes
Colin
Hi Henrik
I’m not completely against split screen viewing, especially if it’s case of simple navigational use. My concern is when I’m trying to understand what a target is doing, especially if it looks like it might affect us. Then I want the least extraneous information possible, as I need to focus on the matter at hand. You’re quite right about ‘the fat finger syndrome’ by the way, when it’s all too easy to crash the system when you least need it. But I’m sure there’s an element of taste and liking what you’re used to, so I am completely open to the advantages of split screen use and I certainly agree that a decent sized screen is a must.
I haven’t seen the cursor cross that you mention, which sounds like a very good idea – I’ll find out more – thanks.
Best wishes
Colin
The desirability of split-screen viewing depends partly on the size and quality of the monitor. We bought a top-line 22″ diagonalPC display when launching in 2004. It is rather outdated today, but is still larger than most yacht MFDs
We will probably replace with similar size better quality monitor soon.
We use split screen a lot. Agree wholeheartedly that weak targets show better on a plain black background (with a few speckles, as discussed above, of course)
Hi Neil
thanks for that, which bears out my own view that a decent sized screen is the only way to go if you want to view split screen effectively. When our MFD bites the dust this may well be the way we’ll go.
Best wishes
Colin
This is the plan for the pilothouse: a biggish monitor on an armature that can lie flat against the underside of the roof when not in use, but which can be brought in for serious nav work when every pixel needs to be seen. If it can be brought without arm’s length of one’s face, it needn’t be bigger than 19-22 inches, but that’s twice the size of most MFDs that aren’t five grand.
Thank you, gentlemen, for an excellent and informative post. I will print this article out and store it near the nav station.
Regarding #7, Orientation, and crew should generally not change settings such as Head-up/North-up and Gain: I have encouraged crew to change the Gain when making a large Range change, because the specks on the screen at 16 miles (my max Range) tend to disappear at 3 miles, which I think means the possibility of missing a nearby target, even though the gain was set correctly at 16 miles. Are you discouraging crew from changing the Gain as a way of simplifying their learning process, or because you do not find much of an improvement in target detection from adjusting the Gain after adjusting the Range?
Richard
Hi Richard,
That’s a good point. I suspect this may be a set-specific issue, so with the behaviour you are seeing I think you are absolutely right to adjust. On our Furuno 1832 we have generally found that we can set a single gain adjustment that works well over the range.
Hi Richard, John
I think this is indeed set-specific. Some sets seem to tone down the gain as range increases, or else there’s some other form of loss that’s inherent in the system. Adjusting the gain is therefore sometimes obligatory.
Best wishes
Colin
In the entry above Colin linked to mvtanglewood.com. This site is written by Peter Hayden and certainly worth a read in my opinion. If you go there, also have a look at other entries.
Here he makes a case for relative motion vector feature and describes how it is often misunderstood or mixed up with “relative motion display” vs. “true motion display”:
http://www.mvtanglewood.com/2015/02/radar-comparison.html
Motion vectors are displayed only when using ARPA or MARPA so they have nothing to do with true or relative motion display. By default, the motion vectors are “true”, meaning they are drawn relative fixed features on land, for example. On some sets, the type of vector can be set to “true” or “relative”. If they are set to relative, then they become much more useful in passing situations as the vectors will then indicate if a target will pass you ahead or astern, and by how far, or if it will hit you. For example, if you have big fast target at a more or less steady bearing and closing, then a CPA value displayed will tell you how close you will get but only the relative motion vector will tell you if the target will pass ahead or astern. Knowing this can be crucial in some situations and will allow you to make a sensible course correction yourself if you would otherwise get too close for comfort.
Very few radars other than “fishermans radars” have this feature and in my experience, it is useless to ask a salesperson. In my attempts so far, I was unable to make them understand this feature so what they told me was nonsense. You will need to download the user manual and dig around in it.
The Simrad MARPA function appears to be fundamentally broken on all of their radars except the HALO open array radar.
Ben on Panbo has put up some screenshots of my 4G on this page:
http://www.panbo.com/images15/hennings-4G-marpa-screens.html
Which is linked to from this entry:
http://www.panbo.com/archives/2015/12/marpa_on_small_radars_is_navico_4g_especially_bad.html
Interestingly, Simrad offers relative motion vectors but as the entire MARPA feature is useless, so are the relative vectors (in my opinion).
In this entry Peter Hayden describes how the NMEA 0183 sentence “TTM” (Tracked Target Message) can be used to integrate a standalone radar, such as those offering the relative motion vectors, with a PC navigation software or even an MFD.
With Rose Point Coastal Explorer, an ARPA target tracked for example by a Furuno 1835 will give an icon and vector on the Coastal Explorer chart that is continuously updated.
The 1835 has a “TLL” button which makes it send a Target Latitude/Longitude NMEA0183 sentence once for each time the button is pressed, giving the L/L of the radar’s cursor position. However, this feature does not work with Coastal Explorer as CE doesn’t understand this sentence.
Hi Henning,
Thanks again for that information on integrating the 1835 with a chart plotter. I will certainly experiment with that when we upgrade.
Thanks guys, I really enjoyed your article – it set me thinking about our set-up.
On the ships I was on with commercial radar sets, we always plotted targets (3 or more “dots” over the target at set 3 or 6 minute intervals joined up on the screen itself), thus highlighting noteworthy targets and their tracks relative to us. Such visual plots were pretty essential when managing multiple targets at one time, such as when transiting the English Channel. Times two in rain or fog – there was too much chance for error trying to keep things in your head. And snap-shots from the radar didn’t tell you much, what was most important was the relative change over time – all too easy to confuse target movements especially when two or more targets were close to each other. At night, who can judge if you are seeing a bright light on a distant target or a faint light on the closer one?
A white chinagraph pencil, a short transparent and flexible graduated plotting rule and a repeating alarm that could be set to 3, 6 or 12 minute intervals were the tools of trade for plotting on screen relative tracks and closing speed. Using the rule and pencil to project the target’s relative track on screen quickly showed the CPA and provided an easy to measure distance to CPA. Then we estimated time to CPA using your “quick and dirty trick” and the distance scale on the screen with simple extrapolation along the track. Vector plots, usually in 3 or 6 minute intervals (12 mins at long range) for any dangerous looking targets quickly showed their actual course and speed.
Keeping the chinagraph pencils sharp so the plot didn’t hide any small targets, and pressing lightly to keep plots and tracks thin was important and doubly so on a smaller screen I would think. A simple arrow head illustrated relative closing or opening direction of the target track, and helped with identification and making collision avoidance decisions. Discipline in always removing old plots with a soft clean cloth as soon as they were clear was needed to avoid missing new, smaller targets.
In poor vis, I always liked having a target’s projected relative track line on the screen, which made any deviation to the plot pattern readily apparent, so indicating a change of speed or course. You had to be careful swapping between screens to return to the same plot scale – I always made a note in the bottom corner of the screen of my original plot screen range and kept plots on one screen at the same set intervals, usually 6 minutes as Colin mentioned – anything to make the maths under pressure easier and remove “errors of calculation” as our examiners deemed them.
I must confess, I have never used our 2 year old radar (coupled to a 12″ chart plotter screen) in ernest, as we almost never have fog here. Even our night passages have all been under clear skies so far, so your article has me thinking about testing it out – has anyone used on-screen plotting on the smaller displays we use on yachts?
You might then be wondering why we have radar at all? We probably wouldn’t for our sailing around NZ, but in areas of poor charting fairly commonplace in the Pacific Islands, it is a blessing – helps a bit for the odd tropical rain squall too. AND is in my view the biggest plus for overlay mode. With poor charts, overlay mode really helps correctly identify, then orient you relative to on screen hazards such as whole islands / reef structures etc, which can be out by as much as 0.5 NM on both your electronic and paper charts (though their positions relative to each other tend to be correct). Even old fashioned chart work is really hard with charts out by so much – oh and don’t expect buoys, beacons and lights to be where they were last time, or at all!
best regards,
Rob
Hi Rob,
I did try on screen plotting years ago, but found it did not really work for me on the relatively small screen of our 1832. Instead, our standard practice is to go into course up as soon as we have a target, mark it with a VRM and EBL, and start the clock for three or six (alarm on my watch). The advantage of locking the radar with course up, rather than leaving it in heading up is that if we do need to change course we don’t lose our plot on the target.
Of course none of the above is a true radar plot, as we used to do on paper, but it does seem to be adequate in most situations, particularly these days when we are most often alerted to a course change by the target by the AIS.
On overlay, that’s a good point I hadn’t thought of. Might be very useful in the Arctic where datums are often off too. That said, I actually find it better to revert to paper plotting, assisted by ranges and bearings (mostly with radar), when the datums are way off as I find that no matter how hard I try the incorrect (in relation to hazards) position of the boat icon on a plotter confuses me.