18″ radomes #6, MARPA & True Wakes edition


Though it’s been a while since I wrote about the radome testing, I still feel overwhelmed with what I’ve learned to date, and not done yet.  And at this point — harbor emptying out, cold and dreary — the images are becoming nostalgic.  On the beautiful day above I was off Camden as the area’s fleet of “dude schooners” gathered for the Windjammer Festival.  Besides enjoying the scene (note the gentle sailing breeze, and also the indication that True Wind and Ground Wind are indeed different, as recently discussed), I intended to use the fleet as MARPA targets.  But I got sidetracked by a feature that partially does the work of MARPA without having to cursor around and select targets.  Click on the screen above and I’ll explain…

Note that I have set the Raymarine C140W in True Motion mode, which means my vessel moves across the chart instead of the chart moving under it.  The C Wide won’t do TM in my preferred Head Up mode, but I’ve gotten used to this North Up display, which resets itself when my boat icon gets about 1/3 from the chart edge.  What’s truly neat is that target wakes, sometimes called echo trails, reflect the target’s true motion, as opposed to their motion relative to my boat, and stationary objects don’t make trails.  Now in this particular screen I have the wake time set too long, which is messy, but you can see how some big targets far ahead are slowly moving my way, while one closer is moving away, and a smaller vessel (light blue on the true color RD418HD scanner I’m now testing) zipped across my path. You can even see that a schooner off to starboard just tacked and a small boat now near Curtis Island came out into the Bay and did a 180.  You can also see Raymarine MARPA in action, here showing each vessel’s true course and speed.  In normal Relative Motion, Raymarine plotters display a MARPA target’s relative speed and motion, which is unusual and takes some getting used to (more on that later).
    As with many advanced radar features, Furuno is a step or two ahead, able to display True Echo Trails even when your radar or radar overlay displays are set to Head Up and Relative Motion.  Both are illustrated below.  Note how The Graves (a ledge that looks like a row of tombstones!) and its Gong show no trail, which they shouldn’t, but how the speedboat just crossing my stern shows a long trail.  Furuno gives the user almost infinite control over these trails — time length, graduated or solid color, which color, etc.    

Furuno_MARPA___True_Motion_Echoes2_cPanbo.JPGThe Garmin 4- and 5000 Series do not do True Motion or True Echo Trails, but like the two systems above are quite good at acquiring MARPA targets when paired with 18- or 24-inch radomes.  In fact, this is an area where touch screen works really well.  The 5212 is not fussy about where you tap the screen, as long as it’s reasonably close to the target, and a tap brings up several buttons including Acquire Target.  Tap, tap…done.  A list of MARPA and AIS targets is also easy to access with two taps, Menu, then Other Vessels.  And I really like the way Garmin displays targets in a fairly standard and conservative fashion in 2D mode, but…

Garmin_2D_Marpa_cPanbo.JPGgoes a little wild in 3D Perspective Mode, as seen below.  The 3D works better in practice than it may look on a static screen shot.  By the way, that Class B AIS vessel I’m following below is Red Sky, mentioned recently, and it’s not showing its name because of the NMEA 2000 AIS glitchThe Simrad NSE, incidentally, doesn’t have True Motion either, but it does have MARPA, though I haven’t had much experience with it yet.  Maybe today!


Ben Ellison

Ben Ellison

Panbo editor, publisher & chief bottlewasher from 4/2005 until 8/2018, and now pleased to have Ben Stein as a very able publisher, webmaster, and editing colleague. Please don't regard him as an "expert"; he's getting quite old and thinks that "fadiddling fumble-putz" is a more accurate description.

7 Responses

  1. Sandy Daugherty says:

    Shock and Awe! I had no inking that any of these concepts were out there, much less available at the push of a button. Once again, you justify your position at the head of the line each morning, Ben!

  2. Furuno Tech says:

    We advise our customers that using True Echo Trails in True Motion or Course Up mode is by FAR the best and fastest way to see the vessel inter-action and improve situational awareness around your vessel.
    The True Echo Trail feature is singularly one of the most under-utilized, yet most important aspects to radar navigation for the average customer.
    I have personally seen more than a few knowledgeable Furuno radar customers use this feature to determine who is tracking their positions in tournaments and in-turn, they use this feature to spy on competitors as well. it is also very useful when traveling with a group of friends. On the contrary, tracking individual ARPA targets requires constant viligence and is not nearly effective in this respect. The True Trail feature is a “Set-It” and forget it mode that will instantly provide tracked target and other details at a glance of the radar display.
    Combining True Trails with Radar Overlay in a 3D perspective showing the actual NOAA Raster/Vector Navigation chart was a breakthrough for Furuno with the NN3D Product Line.
    Thank you for the lucid explanation.
    Furuno Tech

  3. Chris Hallock says:

    What heading sensor are you using with each of these for the MARPA to work correctly?
    Also what is your take at the Raymarine 18″ Digital Dome vs the 18″ HD Digital Dome?
    Thanks for all your work on these units,

  4. Ben Ellison Ben Ellison says:

    Chris, I’ve been using a Maretron SC200 compass on a NMEA 2000 network to give heading to all the MFDs. The Airmar PB200 on the same backbone also delivers good heading info, but I stupidly mounted it level with, and too close to, the magnetron radar stack. It reacts badly to the radiation sometimes, so I turned its heading output off (until I remount it in a better spot).
    I like the true color on the Raymarine 18″ HD dome; it helps to interpret targets and it shows rain beautifully. But other HD features, like dual range and auto speed control, await a software update. It’s also going to cost about $1,000 more than the Digital 18″ dome, putting it up in Furuno UHD territory. The Digital dome should do True Motion and trails similar to the screen above, aside from the colors.

  5. I concur with your comments about target trails. I use them often. Entering a crowed anchorage at night they may be dozens of anchored vessels not a threat and one slowly moving monster container ship. It’s hard to pick out the one ship underway against shore lights. With true trails you can spot the one moving ship quickly. It is also useful when encountering fishing fleets when there are too many boats to track individually

  6. Rick White says:

    I find the SIMRAD BR24 broadband radar very interesting with its close distance detail and low power consumption. I have not been able to find an 8″ screen sized display/multifunction unit that offers MARPA. Is there one coming? Have I missed something?

  7. Ben Ellison Ben Ellison says:

    Rick, The Simrad NSE8, just about to come out, can do MARPA with Broadband Radar. I’ve been testing a prototype NSE12, and like it quite a bit, but have only had limited MARPA experience with it so far.

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