Thoughts about AIS

[colemj]

Originally Posted by Pelagic

Thanks Mark....that was very helpful.

Your radar is "heading stabilized" which cancels out slewing errors but does not allow you to operated in "True presentation"

Downside is that you are limited to only "relative" info on targets since it is fed no ground stabilizing data which would give you TRUE info on targets heading/speed that takes into account current-wind. (That accounts for the discrepancies with AIS since that info is GPS fed)

Before GPS, ship radars could be "Ground stabilized" with an ARPA feature where you identified and aquired a fixed target like island or nav bouy and selected "Land lock " so that radar would stabilize for drift when it used your speed and heading inputs.

I am surprised that today's better yacht radars don't have land lock features and only display GPS data rather than use it to ground stabilize for true motion....maybe they do but I have only seen radar overlay offsets in plotters ??

True Motion North-Up Stabilized presentation is fantastic to use in the multilateral situation I described above when inside the 5 to 2nm zone.

You have a birds eye view of the situation where the land stays put....you and all the other moving targets move in true fashion.

I set target vectors to relative and extend track histories to show previous course headings.

In True Motion course changes are instantly identified with their heading lines and the birds eye view helps to see the intent of others who may not be following the Rules...allowing you to take evasive action if a domino effect occurs.

Highly recommend you find out what is needed to make your radar work in TM and practice using it in daylight when coasting.

Then your AIS overlays would be exactly on the radar Target's rather than slightly offset




In SE Asia... since many targets don't use AIS I find that in congested waters I need to concentrate on getting the best out of my radar.

The kind of problem Mark describes is usually because the Radar settings are left on Automatic and it does not compensate quickly enough for too strong a radar return and the ARPA jumps from Bridge to Bow in target calculations or jumps to another ship as Mark warned

Just when you need it most at close range...ARPA on Automatic settings fail you!

Practice this in daylight.
Set Gain/rain/sea/ tuning to manual.

Play with these manual adjustments in different sea/weather conditions to see how they interact.

The goal is to reduce the very strong close target to the same return value as the inherently weaker targets further out without loosing them in the clutter. Reduce the size of a big ship target to a steady small return

Practice at 3nm range switching down to 1.5nm without target loss in different weather conditions.

Then ARPA info stays consistent without loss or jump as you monitor passing

Our radar does both true and relative motion and uses the fast GPS data for stabilization (I am confused why you keep talking confidently about equipment you haven't used, as well as my lack of familiarity with my equipment). My comment about it lagging behind the AIS is because when a ship makes a turn or change in speed, that data is instantly transferred to our helm by the AIS. The radar must make a few sweeps until this difference in bearing or speed is apparent. This is going to be the case for radar vs AIS regardless - on ours, we see the AIS predictor vector change instantly, while the ARPA vector lags by 5-10 seconds (if the speed is relatively fast - longer if slower).

The transfer of acquisition that I describe happens when a small vessel passes closely to a large vessel. By close, I mean close - picture a small boat passing in front of and alongside a container ship. Not separated by miles. It is that condition when the ARPA sometimes transfers its acquisition. No amount of twiddling with settings that I have been able to accomplish fixes this. However, it is very rarely an issue. I brought it up as one of those "gotcha's" that may not be readily apparent.

A bit off topic, but radar is often debated on CF with regards to who makes the best, etc. When we were looking at radar, we were very interested in the 3G units, but ultimately decided on our Furuno instead.

I just had a look through the B&G/Simrad radar manuals again and realize that our Furuno provides true ARPA automatic data acquisition of up to 30 targets simultaneously, as well as being able to perform true motion presentation - where the others do not. The Furuno also has true dual speed dual scan mode, where I don't see that in the B&G/Simrad (they have dual display, but it is just a copy of a scan at a different scale).

It gets stated in these threads that all present consumer radars have the same performance and features now (leaving aside the pulse/CW difference), and that one can just choose a brand and be done with it.

I have not used any others besides our Furuno. Do any of the others have true ARPA and true motion functionalities? Dual speed and dual scan? I know B&G/Simrad do not (or at least cannot find those functions in the manuals).

If these functions are not common across brands, then that is good information for people deciding on radars.

Mark

[Pelagic]

Originally Posted by colemj

It is an ARPA system fed with a 5hz GPS and 20Hz rate compass. I wouldn't call it commercially "stabilized", and it certainly does not provide the "stability" of class A AIS reporting from other ships.
Mark

I think I may have misunderstood... Is this 5hz GPS a satellite compass? Or does it offer positioning data? That then inputs to Radar to land lock.

If so, then you would have ground stabilized TM without drift.

Mark, I can tell you know your stuff and just trying to clarify problems and tricks for others

I am a big fan of Furuno and am just finalizing replacement of my 2002 Raytheon electronics with a Furuno supplier here in the Philippines.

They are more used to big ship stuff so would appreciate knowing which radar and data inputs you decided upon?

[colemj]

Originally Posted by Pelagic

I think I may have misunderstood... Is this 5hz GPS a satellite compass? Or does it offer positioning data? That then inputs to Radar to land lock.

If so, then you would have ground stabilized TM without drift.

Mark, I can tell you know your stuff and just trying to clarify problems and tricks for others

I am a big fan of Furuno and am just finalizing replacement of my 2002 electronics with a Furuno supplier here in the Philippines.

They are more used to big ship stuff so would appreciate knowing which radar and data inputs you decided upon?

No, it is not a satellite compass - just separate 5Hz GPS (Maretron) and 20Hz rate compass (Simrad). The Furuno definitely does true motion display, but I cannot say whether it "land locks" since I don't fully understand your use of that term. When in true motion mode, it presents the vessels relative to each other with all targets moving across the screen. Overlayed on a chart, the land is "steady" with the targets moving relative to it. Certainly, the speed of display of a vessel's change would be higher and more accurate with a satellite compass.

The other nice thing about the Furuno is that when in split display mode using dual scans, each display has independently controlled gain, sea state and rain clutter controls, along with all other functions like setting one display in true motion and the other in relative motion. One display can even be a chart overlay.

Mark

[Pelagic]

Very nice!
When in TM display... does it offer you the choice of True or Relative heading Vectors on targets?

"Land lock" was the original term used by Radars to take into account set and drift..... Otherwise you would see a small tracking history on a stationary and fixed target like a nav bouy in TM

[colemj]

Yes, you can set true and relative headings independently for vessel and targets in both true and relative motion modes (although I don't understand why anyone would want some of those combinations). The EBL's can also be set true or relative.

Mark

[Pelagic]

I like the True ship Headings when moving through a crowded anchorage like Singapore so you can easily detect course changes of other moving ship's and smaller craft better as they wind around the anchored ships
Especially in heavy rains when visibility is down to nothing

Which Furuno radar scanner did you buy?

I assume you are displaying this on a Furuno MFD?.

[colemj]

The Furuno DS4D displayed on a NN3D MFD. I don't think the functionality is any different on their other scanner/MFD combos. I don't know about their dedicated radar displays.

Mark

[Pelagic]

Great... That is the same setup I have been costing and configuring.

For me, this is not a pi$$ing contest between AIS and Radar but the goal to get the best small yacht size" radar equipment for my monsoon rain area.

Just wish they came up with a switchable S & X Band scanner.

[Dockhead]

Originally Posted by colemj

Our radar does both true and relative motion and uses the fast GPS data for stabilization (I am confused why you keep talking confidently about equipment you haven't used, as well as my lack of familiarity with my equipment). My comment about it lagging behind the AIS is because when a ship makes a turn or change in speed, that data is instantly transferred to our helm by the AIS. The radar must make a few sweeps until this difference in bearing or speed is apparent. This is going to be the case for radar vs AIS regardless - on ours, we see the AIS predictor vector change instantly, while the ARPA vector lags by 5-10 seconds (if the speed is relatively fast - longer if slower).

The transfer of acquisition that I describe happens when a small vessel passes closely to a large vessel. By close, I mean close - picture a small boat passing in front of and alongside a container ship. Not separated by miles. It is that condition when the ARPA sometimes transfers its acquisition. No amount of twiddling with settings that I have been able to accomplish fixes this. However, it is very rarely an issue. I brought it up as one of those "gotcha's" that may not be readily apparent.

A bit off topic, but radar is often debated on CF with regards to who makes the best, etc. When we were looking at radar, we were very interested in the 3G units, but ultimately decided on our Furuno instead.

I just had a look through the B&G/Simrad radar manuals again and realize that our Furuno provides true ARPA automatic data acquisition of up to 30 targets simultaneously, as well as being able to perform true motion presentation - where the others do not. The Furuno also has true dual speed dual scan mode, where I don't see that in the B&G/Simrad (they have dual display, but it is just a copy of a scan at a different scale).

It gets stated in these threads that all present consumer radars have the same performance and features now (leaving aside the pulse/CW difference), and that one can just choose a brand and be done with it.

I have not used any others besides our Furuno. Do any of the others have true ARPA and true motion functionalities? Dual speed and dual scan? I know B&G/Simrad do not (or at least cannot find those functions in the manuals).

If these functions are not common across brands, then that is good information for people deciding on radars.

Mark

This is thread drift, but it's interesting.

FWIW, the 4G radar was one of the main reasons why I went with Simrad/B&G for my new electronics. I am extremely pleased with the plotters, but the 4G radar is not as special as I thought it would be. I am generally satisfied with it, and the very high definition at close range is very useful, but I think that the latest DSP pulse radars from Ray and Furuno are not far behind in this aspect. So for anyone else being driven by radar to choose Simrad -- I would suggest not to make that a main criterion.

I haven't used the Furuno ARPA system (I have, however, seen the Furuno radar picture, and it is very lovely). I don't know whether or not it's going to be really useful to have it acquiring targets automatically. I am not much bothered by acquiring the targets myself -- it's not that much trouble.

What I AM bothered with is the AIS display -- getting back to the original topic. I take it that Furuno systems display AIS the same way?

[colemj]

Originally Posted by Dockhead

What I AM bothered with is the AIS display -- getting back to the original topic. I take it that Furuno systems display AIS the same way?

If you mean that it projects COG vectors, then yes.

Mark

[Paul L]

The Furuno Navnet3D is a great radar and a pretty good chartplotter. But its AIS display is just so-so. At times it can be hard to get the AIS targets to highlight with the cursor and display info. It does not display as much received info on a target as the Vesper unit. There is no easy way that I know of to get an AIS target list -- i.e. a list of all targets sorted by CPA or TCPA. And it does not offer the diagram of the boats positions at CPA, like the Vespers. All of these could easily be added via a software update. But that is unlikely as the development effort at Furuno is primarily on the touchscreen versions.

[colemj]

Originally Posted by Paul L

But that is unlikely as the development effort at Furuno is primarily on the touchscreen versions.

The touchscreen versions don't have any of that either. Furuno actually seems to hate AIS. They refuse to support it over N2K - going as far as to say it will never happen - and they have dragged their feet on any and all requests around supporting it better. Even the company responses to questions about AIS in the support forums seem snarky and dismissive to me.

On the other hand, I know the Zeus can display a list of 3 targets, which is only very slightly better. I don't know how other CP's present AIS.

I do know that Coastal Explorer is very good at AIS display, and OCPN also seems good (I haven't used that as much).

Mark

[Pelagic]

Originally Posted by colemj

On the other hand, I know the Zeus can display a list of 3 targets, which is only very slightly better. I don't know how other CP's present AIS.
Mark

I recently used the Raymarine e127's MFD on a 69ft Ferretti and they also displayed a list of 3 AIS targets.

This was my first time using a Hybrid Touchscreen and I did not like it!
Too easy to make mistakes with boat motion and they even warn you to lock out the touch screen when it gets lively!...... So why bother?

Also I hate that you can only get the manual via the MFD itself..... Not very convenient.

[colemj]

Originally Posted by Pelagic

Also I hate that you can only get the manual via the MFD itself..... Not very convenient.

I would be surprised if RM did not offer the manual as a PDF download. Few things come with a paper manual anymore.

Mark

[Pelagic]

Originally Posted by colemj

I would be surprised if RM did not offer the manual as a PDF download. Few things come with a paper manual anymore.

Mark

I was to.... It comes only as an Apple App ... Not downloadable PDF for other formats.... Read the RM Forums and heard similar complaints.
Was a pain since the new Hong Kong install had some configuration conflicts that was difficult to sort out in the Philippines via the onscreen manual
That is another reason why I like Furuno