OpenCPN SIMRAD/LOWRANCE Radar Overlay PlugIn

[Hakan]

JM..
The given range for the BR24/3G seems relevant according to my experiences and I can't say I've ever asked for more.
Håkan

[rgleason]

That's very interesting. I've written them to request dev a smaller (less windadge and less weight) radar with 12 nm range because or 9' backstay mount will only permit an 8-12 nm line of sight (Iforget the assumptions made for height of distant vessels.) For us there is no way to use the 48 nm except to power punch through weather in the case of a pulse radar.


I have been advised that there will be no smaller version anytime soon (dev costs), and now I have learned that this is the smaller version!


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[BMD21]

RGleason,

I'm curious about what you're asking. Do you want a smaller diameter radar to hang off your backstay? I believe that would have little effect on the range, because that's a function of signal to noise ratio of the received signal. That's the reason for the 3G chirp pulse which gives better correlation and can use a lower S/N ratio. I wouldn't think that a non-chirp pulse radar of equivalent rating would be better than a chirp pulse radar in penetrating rain. And in Southern California, that's not an important consideration.

Resolution is what would suffer since a smaller radome diameter means a smaller antenna width. This in turn would reduce the resolution, which is a function of the antenna length. Both the 3G and 4G advertise the same horizontal beamwidth, 2.6 deg, and have the same radome size, but the 4G has a range of 36 miles vs the 3G of 24. And, obviously the 4G uses more power than the 3G, both in and transmit.

Certainly you're correct in saying that small boats have a vary limited horizon range, since they don't have the radar at any great height. That's why I bought a 3G, ignoring the 4G's call for bigger and better for just a few bucks more. 24 miles is more than enough for me. Actually, if the radar is 20' above the water the horizon is 6 miles away. I believe that my experience with small boat radar is that it's useful up to 16 nmi and anything over that is not to be trusted.

Anyway, the important point is that the 3G works well with OpenCpn and makes a safer navigation effort. Glory be.

Boris

[rgleason]

Boris thank you. I did want a smaller lighter radome. However reduction in res would be an undesirable result, so I guess the 3g or 4g is ok. Do you know what you draw when on and when on standby for 3g? Is it about what factory specs show? Do not know why I would want 4g.

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[BMD21]

Well, how about that. Just as we complete this discussion of chirp radars, Panbro has an article on Navico/Simrad Halo radar. This appears to be an improved version of 4G. What is appropriate is that there is a discussion of the limitations of 3G/4G radar at long ranges and how Halo overcomes it. Also there's a comparison of "power on target" for both modulation techniques. They explain how chirp radar penetrates rain and the claim is, better than non-chirp (bang) radar.

There's a number of slides to wade through, but the link is www.panbo.com/archives/2015/05/how_simrad_halo_works_12_radars_in_one_.html.

I assume that Halo will have the same interface with OpenCpn as the present radars. We can only pray.

Boris

[blubaju]

Originally Posted by BMD21

Well, how about that. Just as we complete this discussion of chirp radars, Panbro has an article on Navico/Simrad Halo radar. This appears to be an improved version of 4G. What is appropriate is that there is a discussion of the limitations of 3G/4G radar at long ranges and how Halo overcomes it. Also there's a comparison of "power on target" for both modulation techniques. They explain how chirp radar penetrates rain and the claim is, better than non-chirp (bang) radar.

There's a number of slides to wade through, but the link is www.panbo.com/archives/2015/05/how_simrad_halo_works_12_radars_in_one_.html.

I assume that Halo will have the same interface with OpenCpn as the present radars. We can only pray.

Boris

In my understanding 3G/4G are radoms, Halo as far as now only open scanners. Pls. correct me if I'm wrong. As my E120 Raymarine is about to quit (some heat problem, after a few hours in use it starts rebooting, but maybe the old AIS-overloadproblem) I am looking into this Navico stuff. Sidetopic: what display/keyboard is mostly used in the cockpit with oCPN?

[BMD21]

blubaju,

You're absolutely correct, Halo starts with a 3" non-enclosed antenna and they go up from there. The reason I mentioned them is the Panbro link, where they discuss some 3G/4G shortcomings and how they've overcome them. Plus a lot of insight into chirp radar.

If you're going to get a new radar this would be a good time to switch over to OpenCpn and 3G (or 4G or Halo.)

Boris

[Douwe Fokkema]

I have put a new beta version of the BR24radar_pi on the github:
https://github.com/douwefokkema/BR24...i/tree/master/
It is to a large extend identical to the previous version. However the initialization has been improved, specially for new installations where the .ini or .conf file is not yet present. This version also runs on Ubuntu 14.04 with wxWidgets 3.02 and OCPN 14.1.
Under Windows we have tested with OCPN 4.0. The dll for Windows is attached (remove the .pdf extension).
With thanks to Hakan for adding the timed transmit and all the testing.

Remark: This forum was not intended for general discussions of the pro and cons of various radar types but for discussion of the OpenCPN SIMRAD/LOWRANCE Radar Overlay PlugIn.

[Hakan]

Originally Posted by Douwe Fokkema

I have put a new beta version of the BR24radar_pi on the github:................
This version also runs on Ubuntu 14.04 with wxWidgets 3.02 and OCPN 14.1.
Under Windows we have tested with OCPN 4.0. .........

For info; I've built and tested Douwes version using OCPN 4.1.427, including xwWidgets 3.0.2, both in Win(XP&7) and Ubuntu 12.04.

Håkan

[rgleason]

Hakan Do you know if the plugin, Douwes version, is still compatible with earlier versions of opencpn? Which opencpn.lib was used? Does the use of wxwidgets 3.0.2 make a Plugin not compatible with earlier opencpn versions?

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[Hakan]

Originally Posted by rgleason

Hakan Do you know if the plugin, Douwes version, is still compatible with earlier versions of opencpn? Which opencpn.lib was used?

Yes it is, pls see previous two posts for a listof tested OS

Does the use of wxwidgets 3.0.2 make a Plugin not compatible with earlier opencpn versions?

No not for BR24Radar_pi, the plugin isn't changed after OCPN wx3 implementation. It was just probably well prepared by Kees.

Håkan

[merrimac]

For those interested, we (= Douwe, Håkan and me) are finishing up on v1.2 of the plugin.

It will be the final version that will work with OpenCPN 4.0.0 on Windows, the next version will be for OpenCPN 4.1.x with wxWidgets 3.0.2 only. This will probably be true for Linux as well.

The OS X version will not be affected as it already used wxWidgets 3.0.2 in 4.0.0.

If you want to test, and have a compiler and a Navico radar, please head to https://github.com/canboat/BR24radar_pi to get the latest source version.

The 1.2 release will be released before June 1 (as I am going sailing ... )

[dave777]

Minor problem, but it works for me Ubuntu 14.04 with current OpenCPN.
Overall, it is very impressive. The UI for access to the radar settings is much easier to use than the plotter itself.

The problem is that with the radar image simultaneous on my PC and my plotter, the plotter radar aligns correctly with the bridge, but the PC radar is offset by perhaps 15 degrees.

What data would the developers like to see in order to hunt down this anomaly?
Thinking out loud: the chart I use 90% of the time is "skewed", a red slash displayed on it. Does the plug in account for using a skewed chart?

Compliments to all the Navico radar developers, and OpenCPN as well of course!

[merrimac]

Originally Posted by dave777

The problem is that with the radar image simultaneous on my PC and my plotter, the plotter radar aligns correctly with the bridge, but the PC radar is offset by perhaps 15 degrees.

This is probably two effects: your radar is rotated relative to the front of the boat and ...

Originally Posted by dave777

Thinking out loud: the chart I use 90% of the time is "skewed", a red slash displayed on it. Does the plug in account for using a skewed chart?

Dunno, I don't know how O handles skewed charts.

But the solution is at hand -- Go to settings > Plugins > BR24radar_pi > Preferences. You get a dialog where you can add a rotation offset.

Originally Posted by dave777

Compliments to all the Navico radar developers, and OpenCPN as well of course!

Thanks!

[dave777]

Originally Posted by merrimac

This is probably two effects: your radar is rotated relative to the front of the boat and ...

I can confirm that there seems to be a bug with Navico radar plug-in: skewed charts display "un-skewed" radar return data.

After making the above post, on my next trip to the boat I looked at radar images for skewed and normal charts. The normal charts have the radar image aligned correctly to land masses and bridges, but the skewed charts have the images rotated. I believe that the amount of the erroneous rotation is exactly the amount that the chart is skewed. My guess is that the math OpenCPN uses to adjust for a skewed chart does needs to be accounted for by the plug-in as well.

This could be a safety issue for people who don't normally use a skewed chart if a skewed chart is swapped in on a voyage, the return of another ship would be shifted.

Let me know if there is any data or tests you would like me to run.

Thanks again!