MARPA vs Motion Scope

JPGator

Active Member
Apr 25, 2019
495
Treasure Coast
Boat Info
2008 Sundancer 40
Engines
Cummins QSB 5.9 425HO
Adding radar and I’m between Fantom 24 and 424 HD2. The main difference is the usable distance but more importantly the Fantom has motion scope where the HD2 does not. If you have MARPA why do you need motion scope?
 
I have the Fantom 54 and in the beginning stages of fully understanding it; but I had an analog RM Pathfinder before so there is quite a learning curve for me. So, MARPA is an internal algorithm that calculates change in position of the target relative to your boat's heading and speed and roughly establishes velocity and direction; it does this once a revolution of the scanner but the algorithm requires quite a few scanner revolutions to firm up the target. There is also the need to identify and command a target to MARPA. I think 12 (needs verification) MARPA targets can be simultaneously tracked. The Garmin Motion Scope uses the doppler effect to more immediately assess the target (it can assess immediately due to the digital pulse technology) and paints the target depending upon direction, threat, and velocity. Motion Scope can track and evaluate unlimited targets and is automatic (you don't need to select like MARPA). So far I'm really liking it and it's overall detail; heck it paints the wake behind my boat.
Besides the gee whiz of the Fantom I've been putting my boat on an electrical diet to eventually move over to Li batteries and the digital pulse technology reduced the electrical current for the radar by close to 20 amps.
 
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I read it the opposite. MARPA is manual. You have to look at your screen, identify the target manually, then wait for MARPA to track it. Motion scope, from what I have read, does this automatically and just starts tracking targets, allowing the driver to focus on what’s going on. Motion Scope sounds way better.
 
Yep you got it backwards - doppler (Motion Scope) is the best most accurate option for target identification and evaluation; everything will be digital pulse with doppler effect in the near future. I'm now hearing digital radar without a rotating element is nearing the market. Depending upon your settings you can track for threats and the system will alarm you of a collision potential. Now in Motion Scope you can create a MARPA target from a Motion Scope target to uniquely track and identify until out of range. So let's say you have a friend at night in another boat you are following or watching; It's showing in Motion Scope and you have their direction and velocity. You have, by the way twenty other targets that you are paying attention to and driving the boat. Simply touch the target (touch screen) of interest and it becomes MARPA; you will be able to instantly identify that is your friend regardless if you continuously watch the screen or not. And the MARPA target remains being tracked and data gathered by the Motion Scope technology. MARPA and Motion Scope are quite different in purpose.
 
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I also recently installed the Fantom 54 and still learning but I have been impressed by the Motion Scope. As ttmott mentioned it paints the targets depending on direction, green moving away and red moving towards your boat. I debated whether to spend the extra $$$ on the Fantom but happy I did.

Rob
 
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Not familiar with Motion Scope but did use MARPA all the time as we traveled in the offshore shipping lanes to avoid local fishing fleets. MARPA is invaluable as it is difficult without navigation aides to see visually if you are going to cross the courses of 500-600 foot freighters. I would tract multiple targets that were often 10-12 miles out. MARPA gives you target headings, their speed, ETA, and how close you will be when you pass them. It alarms you if you pass inside of safety margins you establish. This is particularly helpful in fog and reduced visibility situations.
 
View attachment 84880 View attachment 84879 Not familiar with Motion Scope but did use MARPA all the time as we traveled in the offshore shipping lanes to avoid local fishing fleets. MARPA is invaluable as it is difficult without navigation aides to see visually if you are going to cross the courses of 500-600 foot freighters. I would tract multiple targets that were often 10-12 miles out. MARPA gives you target headings, their speed, ETA, and how close you will be when you pass them. It alarms you if you pass inside of safety margins you establish. This is particularly helpful in fog and reduced visibility situations.
Me too, I used it a lot when crossing the shipping lanes.
Motion Scope is a Garmin trade name for how the display shows moving targets that are acquired and translated using digital pulse radar and doppler frequency shift analysis - nothing more. Just newer, better radar....
MARPA is still a valued feature with the Garmin system and but a touch away, Same MARPA but newer, better, and easier to use.

Now if only this fancy radar saw the crab pots at night.... Don't ask....
 
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Pretty sure the Fantom 54 is also a low power, solid state device (no magnetron), so the radiation hazard is much less (50w vs 4kw for the 424 HD)? Maybe not a consideration, but I sometimes check the radar for rain/storms during the summer, and it’s nice to know it doesn’t matter if I have people sitting on the bow of the boat, and I am guessing less of a drain on the batteries?
 
I know most of you are Garmin fans but Furuno has ARPA. No manual anything it’s automatic. Also has NXT which is their trade name for fantom. I’ve been impressed with my system from day one.
 
I know most of you are Garmin fans but Furuno has ARPA. No manual anything it’s automatic. Also has NXT which is their trade name for fantom. I’ve been impressed with my system from day one.
How do you identify and track one target amongst many like the MARPA does if everything is highlighted automatically as "ARPA"?
All of our modern radars automatically track and provide warnings for all moving targets but MARPA provides the added feature to select, highlight, and uniquely track/watch an individual (up to several) target.

From Wiki
Mini-automatic radar plotting aid (or MARPA) is a maritime radar feature for target tracking and collision avoidance. Targets must be manually selected, but are then tracked automatically, including range, bearing, target speed, target direction (course), CPA (closest point of approach), and TCPA (time of closest point of approach), safe or dangerous indication, and proximity alarm. MARPA is a more basic form of ARPA (automatic radar plotting aid).
User selected Targets are initially highlighted with a small box whilst MARPA resolves the relative motion by comparing the relative motion of the target on the screen with the true, actual motion (speed) of the tracking vessel. Once resolved the acquiring box will become either a Circle for safe targets or a triangle for dangerous targets. MARPA can indicate further information with 2 very different but similar looking vectors: True Vectors and Relative Vectors. True heading and speed of a target can be ascertained with a True Vector, the length of the line indicates the distance the target will actually cover per duration of vector, usually 6 or 3 minutes (this is user selectable) although, range permitting, the 6 minute vectors provide quicker mental calculation of speed. E.g. True 6min vector (TV6) of 0.75 NM indicates the target's true speed is 7.5 Knots, the direction of this vector indicates the vessels heading relative to the tracking vessel or its electronically fed heading if one exists. The relative motion of a target can be seen with Relative vectors, these just show the future position of the target on the Radar screen as per Vector Duration, again usually 6 or 3 minutes depending on range in use. A relative vector of 6 minutes (RV6) would be a line representing the movement of the target for the next 6 minutes.
Most colour Radar displays can show both TV and RV simultaneously. It is essential that users of MARPA not get confused between RV and TV, especially on Radars that cannot display. True vectors allow users to determine the aspect of a target at a glance, something otherwise requires manually plotting, Relative vectors provide, at a glance, information about which vessels pose a collision risk; a RV pointing at the centre of the Radar screen indicates a risk of collision. All the information pertaining to a target is also available numerically, but when tracking multiple targets this information distracts the user from the image. With proper training, viewing vectors is much safer.[1]
Manufacturers use a variety of acronyms for the small crafts or yacht, e.g. MARPA (mini or manual ARPA, depending on which company you talk to) is the dominant one. MARPA, ATA (automatic tracking aid), and ARP (automatic radar plotting) all similar functions to ARPA. The major difference of this Radar plotting aids may not be fully equivalent to all ARPA performance standard of IMO approved type which is a mandatory requirement for large ocean-going ships. Therefore, they are less expensive for small craft.
 
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Furuno tracks 100 targets automatically. All you have to do if you want the information it is tracking is touch the target on the screen and it pops up instantly with all that targets information. No multiple button presses or anything simply touch the target and the info is there for up to 100 targets.

You do have the ability to “acquire” a target which then numbers that target and plots circles it on your radar with the heading overlaid. I can send some pics of you’re interested.

Garmin is good equipment and I’m not knocking it at all. Their plotters are intuitive but Furuno radar has always been class leading so it amazes me how much share Garmin is taking. Probably a discussion on another thread but I really believe it’s their marketing and outlets where they sell it.

Here is a link to the NXT brochure which does a good job explaining.

https://www.furuno.com/files/Brochure/334/upload/DRS-NXT_Brochure2.pdf

The op was asking about the difference of MARPA and motionscope and I think that was answered above. In my explanation the Doppler effect shown on the screen with the direction of travel and dangerous targets is motionscope (or NXT in my case with Furuno). MARPA or ARPA is the system that gives the operator more information to track specific targets that may become dangerous to your course or track. They are different things.
 
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Furuno tracks 100 targets automatically. All you have to do if you want the information it is tracking is touch the target on the screen and it pops up instantly with all that targets information. No multiple button presses or anything simply touch the target and the info is there for up to 100 targets.

You do have the ability to “acquire” a target which then numbers that target and plots circles it on your radar with the heading overlaid. I can send some pics of you’re interested.

Garmin is good equipment and I’m not knocking it at all. Their plotters are intuitive but Furuno radar has always been class leading so it amazes me how much share Garmin is taking. Probably a discussion on another thread but I really believe it’s their marketing and outlets where they sell it.

"You do have the ability to “acquire” a target which then numbers that target and plots circles it on your radar with the heading overlaid."
This is the modern MARPA.
 
With Garmin it is a manual process. With Furuno it is automatic. Also I believe Garmin can track 7 manual targets and Furuno Automatically targets 100.

Very similar I agree but I have all of those targets automatically. It’s just allowing me which ones to display.
 
With Garmin it is a manual process. With Furuno it is automatic. Also I believe Garmin can track 7 manual targets and Furuno Automatically targets 100.

Very similar I agree but I have all of those targets automatically. It’s just allowing me which ones to display.
I think you still have a bit wrong:
You can uniquely select and identify between one and 10 targets (Garmin) and they are HIGHLIGHTED as MARPA; this is one feature that you can use to select and monitor targets.
Primarily, however the Garmin and most others simultaneously track and provide warning (collision threat for example) for thousands of targets as normal radar operation. The old radar systems had to have a target identified as MARPA to track and provide warning but that has all changed.
Furuno, Raymarine and others are essentially the same.
 
I’m not sure how you think I have it wrong. Garmin tracks 10 manually selected targets. Furuno automatically tracks all targets within 3nm. See attached.
 

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My understanding: Garmin Fantom 54 automatically identifies and tracks targets (Motion scope), also allows manual selection (MARPA, 10). Garmin 424HD2, only the latter.
 
All the new doppler radars can do these functions. It has to be doppler to identify moving vs stationary targets. I chose the Raymarine Quantum 2 Doppler and pretty happy with it. It color codes things moving relative to me (red towards, green away) and can automatically acquire and track 25 targets, or manually track 10(?) targets.

The doppler color coding is the most useful in small confined areas. The automatic mode pick up too many targets to be useful, but on open water, I think it would do a pretty good job although I think adding alarm or safety zones would improve it, but haven't spent enough time to say.

The other useful function is the Truetails. a virtual wake behind the taget, tell you were its been.

Choose your radar on what your needs are. If your looking for short distance naviagtional capabilities the doppler domes are excellent (mine pick up the no wake bouys around the marinas easily out to a mile and as close as I can see over the bow). Operating on bigger water/longer distances, the open array dopplers are even better (open array gets you better target differentiation at long distances). If your a fisherman, the old X band stuff is superior for finding birds at a distance, but you lose all the benefits of the doppler radars.
 
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I had a Fantom 24 dome installed on my boat last season. It was my first experience using radar so I can't compare it to another system. While I haven't had a ton of time with the system I found the doppler-enabled Motion Scope function very helpful in a couple of cases.

One was coming out of the Niantic river, which can be very crowded. There was a sailboat near my course and due to conditions I could not readily tell visually if it was headed away from me and a correction was needed, or toward me and I could maintain course. The Motion Scope function easily showed it was headed away me. I was able to take proper action early. I later realized that part of the issue was that it was as canoe-ended boat it was visually deceiving.

I've had a couple other similar situations where the motion scope was very helpful. The radar helped me pick up small boats way before I found them visually, which of course is the point of radar.
 
Garmin has added the capability for MARPA automatic acquisition of targets. I think it was done via one of the software releases this year as it is not in last year's manual. I noticed it while setting up chart screens for a transit. It's activated via Menu > Layers > Other Vessels > MARPA > Auto Acquire on a radar or chart overlay screen.
I had one screen set up for it today on a 130NM trip. I ran into a fur ball of fishing boats at the mouth of our home river and seeing the MARPA auto-targets was actually quite helpful in getting through the mess. They were too concentrated for the doppler trails to be entirely useful but seeing each target as a track with course and speed was very useful.
There weren't an awful lot of contacts the rest of the trip but the radar did acquire most of them. There were a couple of small, fast movers that it didn't acquire but they didn't show up well as radar returns either. We had rain most of the trip and I think the radar was not tuned especially well for the conditions and I need to work on doing better at that. The documentation is typically sparse as is usual with Garmin for both the radar overall and this new capability.
The radar did acquire most buoys and some pieces of land. I don't see a spec for number of targets but I would say it's at least 30. The new documentation seems to indicate the capability interacts with MotionScope(doppler), guard zones and boundaries; I need to play with those to see if I can cut down on unneeded targets.
 

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