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Tuesday, February 9, 2016

Integrating Radar with Coastal Explorer

Back when I was defining V2.0 of the electronics for my boat, I made the decision to forgo a key feature - Radar Overlay.  Radar overlay is a feature that displays the radar return "overlaid" on your chart plotter so you see both the chart and radar return together on the same screen.  In my early years using radar I ran in this mode 100% of the time, and considered it a mandatory feature for any navigation system.  But over the years I have done a complete 180 on that view and now run exclusively with radar and charts in separate windows.  As a result, I was very comfortable forgoing that feature in my new electronics system, and instead opted for Coastal Explorer as my Charting program, and a couple of Furuno dedicated radars.

So what happened and why the change?

I think it all has to do with me practicing and learning over the years how to read a radar return, getting comfortable with it, and being able to quickly correlate what's on the radar screen with what I see outside the boat and on the chart.

In my early years using radar I really liked overlay.  Having the radar returns on the chart placed everything in context, and made it clear when a radar return was a rock pile or buoy as opposed to a boat.  This made reading the radar much easier.

The down side was that the radar returns sometimes obscured what was on the chart.  For example, the radar blip would make it impossible to see what the number was supposed to be on a particular buoy.  The reverse was a problem too.  Lots of info on the chart like soundings, contour lines, and bottom composition sometimes obscured a small radar blip and caused be to miss things or not see them as soon as I might have otherwise.  But these downsides were worth tolerating to have the radar return in context on the chart.

The screen shot below illustrates this.  On the left is a chart with radar overlay, and you can clearly see how the pink radar return correlates with the coast line and channel buoys.  It's a great training aid for practicing and learning how to read a radar return.  But you can also see how it becomes harder to pick out the boats and other moving targets on that screen given everything else that is presented.  And it's harder to see the details on some of the buoys on the chart because of the radar returns.  When you look at that chart, do you readily see all the boats that are around you?

In contrast, now look at the right had side which is a radar-only display.  To an unpracticed operator, it might be a bit harder to correlate what you see with the chart, especially if they are at different scales, but you have to also admit that everything stands out very clearly.  Just look at all those boats around you that you probably didn't see in the left hand overlay view.

What I have found over the past year or two is that I now always use separate chart and radar windows.  And I attribute it to having become more comfortable and fluent at reading the radar returns, and not wanting to miss anything on them.

With all the marine electronics vendors, the radar data format is proprietary, and only their chart plotters can overlay their radars.  There are a few cases of products that have reverse engineered very basic radar display like in OpenCPM, but I don't think any of them provide full functionality including things like ARPA.  It's basically a way for electronics vendors to get you to buy into their whole system of equipment.

But, if you are willing to forgo radar image overlay on your charts, you can have something that I think is even better using Coastal Explorer and many radars.  And it's all done using standard, non-propritary interfaces.  The key is the Target Tracking Message, or TTM.

Lots of radars, when tracking an ARPA target, send a periodic TTM message.  This message describes the target, it's position, it's tracked course and speed, and calculated CPA and TCPA.  It's basically all the info that your radar displays about a tracked target.  All you need to do is feed that message to CoastalExplorer via an 0183 port, and CE will display all those targets including their motion vectors.

Support for Target Tracking Message (TTM)?
Furuno FAR 2xx7 family
Yes (verified with CE)
Furuno 1835, 1935, 1945
Yes, with optional ARPA card installed.  (Verified with CE)
Furuno NavNet3D Family
Furuno TZTouch Family
Furuno FR8065, FR8125, FR8255
Simrad NSO EVO 2, NSS EVO 2
Raymarine Lighthouse 15
Manuals don't appear to list supported sentences, but some users report TTM supported on some models

My radars both display AIS targets, and of course display ARPA targets, so I can see both.  With a radar properly interfaced to CE, it too will display both AIS targets and ARPA targets, in context, on your chart.

In the screen shot below, we are approaching a fleet of a dozen fishing boats.  A few have AIS, but most do not, so I have acquired them with ARPA and am tracking them just like the AIS targets.

Approaching a fleet of fishing boats.

Now, in the shot below, you can seem them all on the chart as displayed by CoastalExplorer.  The AIS and ARPA targets are clearly distinguishable (blue vs red+green), and the ARPA targets faithfully reflect their status:

  • Round targets are acquired and tracking
  • The triangle coming towards us is a dangerous target
  • The square targets along the southern shore are still being acquired, so I know where they are, but I don't yet know their movement.

The same fleet on CoastalExplorer

To me, this now gives the best of all worlds.  My chart isn't cluttered up with radar echo returns, yet it  clearly shows the parts of the radar return that I care about and need to pay attention to, namely the ARPA targets.  And my radar screen is clear of chart clutter minimizing the risk that I will miss something.  With this arrangement, I no longer see any added value in radar overlay.

If I have you convinced this is a great feature, then read on about how to activate it.  It's very easy.

  • First, you need to confirm that your radar transmits TTM.  All that I've looked at do, but that's not an exhaustive list.  There might be some configuration settings in your radar to enable TTM, and you might need to set the baud rate.  Standard NMEA 0183 is 4800 bd, and high speed 0183 is 38kb (38,400 to be exact).
  • Next, figure out which output 0183 port you want to use on your radar.  You can use a free port, or you can use one that is already in use.  Multiple devices can listen to an 0183 channel, but only one can talk.  In this case, you need a port where the radar is the Talker.
  • Now you need to get the data from the radar into your computer running Coastal Explorer.  First check to see if there is already a port going into CE from your radar.  For example, if your radar is part of a multi-function chart plotting and radar system, you may well already be feeding data from it to CE.  If that's the case, then you already have the needed connection.  If not, you will need a free input port.
  • It's a bit of a side track, but the ports on your computer REALLY should be RS-422 ports (two signal wires for transmit, and two signal wires for receive) to be compatible and dependable with NMEA 0183 data.  Most PC ports are RS-232 (single signal wire in each direction) and they are NOT necessarily compatible.  You might get lucky and find it mostly works, but you also might not get lucky.  Or you may think it's working fine when it really isn't.  When I was experimenting with this last summer, the only interface device I could find in Juneau was an el-cheapo RS-232 interface adapter.  On the surface it appeared to work (my ARPA targets showed up on the CE screen), but when I used CE's TroubleShooting screen to examine the NMEA sentences coming in on the port, there were lots and lots of scrambled and corrupted sentences.  I now have a proper RS-422, and it is completely error-free.
  • If you need to make a new connection, run the wires and connect the Radar Talker wires (transmit) to the CE Listener (receive) wires.
  • To test, go to the Configuration page on CE, then click Troubleshooter.  Select the port number that you expect TTM to come in on, and click the Sentences tab.  The window will now show the NMEA sentences being received.  Acquire an ARPA target and you should start to see the TTM sentence coming in from the radar.  If there isn't a check mark next to the sentence, check it to enable it.
Good luck, and enjoy this hidden gem of a feature in CE.


Howard Tucker said...


What made you choose CE vs other options, specifically Maxsea Timezero?

Peter Hayden said...

Hello Howard,

I used MaxSea Timezero for a few years back when I had a Furuno NavNet 3D system. As you may know, Timezero is also the software in the Furuno NavNet3D, TZTouch, and TZTouch2 chart plotters. MaxSea is approximately half owned by Furuno, so there is deep collaboration.

Much of it can be chalked up to personal preference, but I never liked MaxSea TimeZero. Despite the name, it actually seemed to zoom very slowly and generally be sluggish. And I never liked being captive to MapMedia (another jointly owned Furuno MaxSea entity) for charts. Granted, the underlying charts from MapMedia come from well know sources like C-Map and various governmental organizations, but they were always 6 months to a year behind. I had two distinct run-ins with this, once in Canada where the C-Map chart would disappear when you would zoom in on certain areas. When I inquired, c-map had already fixed it, but MapMedia had not picked up the change, and MapMedia was a big black hole for support. In fact, they never responded to my inquiry. I ended up having to buy yet another set of charts form a different source for the 200 nm affected area. Needless to say, I has not a happy camper. Then it happened again in the Bahamas where on the explorer raster charts, Great Sail Island was miss-located by about 1/2nm, but only at certain zoom levels. As you would zoom in and out, it would jump 1/2 east/west. Once again, MapMedia was a giant black hole for support.

In contrast, CE uses charts from as wide or wider a collection of sources, but all are directly from the vendors without a middle man.

And I just never liked the way MaxSea worked. It integrated with the NN3D plotter and radar, but never seemed to do the same thing twice in a row the same way. At the time I was still a fan of radar overlay, so that aspect I liked, but otherwise I just never warmed to it.

The bottom line it that once I started using CE, I never looked back. I still have a valid license to MaxSea, but haven't used it in a couple of years.

If you go back in the blog and start here you can follow my fractured thought process as I contemplated different chart plotters, and chart diversity and availability. If you then read forward in the Electronics Category, there are a few more posts where I finally realize that the MFD is not the center of the works for the electronics on a boat, but something like CE or MaxSea really is. In my case, CE was the best fit. I paid about $300 for it back in 2010 when I went to Antarctica because I wanted to have charts and track our trip. It was the only thing that would work with the Chilean charts of the area, the Falklands, South Georgia, and the Antarctic Peninsula. It's the best $300 I've ever spent on boat equipment of any kind.

Henning Duerr said...

Many thanks for this post, Peter! I have been checking here frequently for just this information.
On the 1835 there is a prominent "TLL" button. If your 1835 is connected to CE and pressing that button does nothing, then CE probably doesn't understand it. TLL is probably the intended feature to verify rock piles (as it is a one-time operation vs. continuous tracking).
Did you (have to) wire up the 1835 as described in this document to get TTM interfaced to CE?

I have these questions:

- What are the reasons for not using auto-acquire? My Simrad NSS keeps losing acquired targets (that were tracked for at least a short while) and I don't know how other radars do in this department (also my radar scanner is only 12ft off the water where you have much more). At times, my NSS is losing the targets faster than I can (re-) acquire them and besides, I have other things do at least some of the time. So I was looking at auto-acquire as a way to solve that problem.

- Do you set the radar to north-up in order for it to better match the chart in CE and, if not, why? Or do you set CE to course-up? If they are not set the same, why isn't that a problem?

Peter Hayden said...

Hi Hennng,

The one time I playd around with TLL I think it was with my 2117. I'll try to give it a more thorough try over the next few days. I agree it's more suitable for verifying the location of static objects.

Interfacing to the 1835 radar is quite simple. Just grab either if the 0183 outputs and feed it to CE. I had never seen the document you liinked to, but note that it's for the ARP-10 board. I have the ARP-11 board which might explain the difference. The ARP-11 board just plugs right into the 1835's main board. I don't think there were any cabkes at all.

I think the answer to both your other questions is "personal preference". I run with true heading everywhere (IMO radars will accept nothing else), and I set up the compass rose around the radar screen to display true bearings, not relative. And my cursor location also reports out as a true bearing. EBLs as welll. I can't come up with any sound argument why it's better. I just prefer it.

It's probably a bit odd, but I run CE in North up display, and I run my radars in heading up. I can only justify it with the "personal preference" trump card. I always want to see maps and charts north up. But I think because the radar is more used to steer and negotiate passages of one sort or another, I like it to correspond to what I see out the windows.

I think any combination can work fine once you get used to it, and getting usd to it can be the hardest thing.

Oh, auto acquire. I almost forgot. I don't have trouble with lost targets, so once acquired they stay acquired 90% of the time. The only time I lose them is in close when I'm set o a lomger range and they get lost in the close-in sea clutter, or when two targets pass each other or pass a buoy and the ARPA lock jumps from one object to the other.

I think if I were in a very busy harbor then auto acquire might be more attractive, or on a passage as an automatic alert system. But so far, mousing over the target and pressing the Ack button has worked pretty well..

Peter Hayden said...

Henning, I tried the TLL (Target Lat long) button on the Furuno 1835 radar. It sends a single TLL message which is received by CE, but CE does not plot anything. Too bad. It would have been nice if it did.

Peter Hayden said...

Just a quick update that when I said "pretty much all radars send TTM" (or something close to that), I spoke too soon. According to the manuals for the Furuno NavNet 3D product family and the TZTouch product family, they DO NOT send TTM. I haven't tried this personally, but it doesn't sound promising. If anyone learns differently, please let me know.

I'm going to update the posting to reflect this, and will probably create a table listing who works and who doesn't.

Henning Duerr said...

According to the installation manuals, Simrad NSS, NSS evo 2 and NSO evo 2 do output TTM (also TLL). But as you have documented at length, since the MARPA vectors are completely off, that is of little value...
Well, at least the MARPA target position would be there.

Peter Hayden said...

Check out the table that I added to the body of the article. It shows which radars send TTM, at least according to their manuals. If anyone can verify any of these and/or provide more accurate data, I'll happily update the table. My quick scan of manuals was not as complete as I might like. For example, I could find no reference to TTM in the Raymarine Lighthouse 15 (their MFD software) manual to TTM, nor in the installation guide for one of the MFDs, but I have read reports from owners who confirm it sends TTM at least for some model(s).

Brian Smith said...


Great article - as well as the previous one about what to buy to replace your Simrad system. But for the life of me, I can't figure out what Furuno radar you have as your primary. Looks like a Furuno 1835 is your back-up, but what's your primary?

I'm replacing 14 year old Raymarine electronics on a boat we just acquired, so your articles are gold! Thanks for writing them.


Peter Hayden said...

Brian, that's pretty funny. Looking back, I see I never called it out very explicitly, but it is tucked into a few articles along the way. I guess that's the down-side of a bog's stream-of-consciousness nature.

It's touched on in the following articles:

But I'll save you the trouble. The primary radar is Furuno FAR2117, black box, DC power. It's a 12kw, 6' open array. The secondary, as you surmised, is a Furuno 1835 which is a 4kw, 24" dome.

Brian Smith said...

Thanks, Peter!