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Open CPN Polars


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OK Guys, I said the other day I was working on the Polar stuff for OpenCPn. It's not public release yet, but I now have it working;

 

[attachment=0]OpenCpn with Polars.jpg[/attachment]

 

You can manually add Polar data, import it from a spreadsheet or several other apps, or build your own from NMEA data being fed to opencpn.

 

For those who don't see the point, or don't know what polars are - Polar files tell you what speeds you should be doing on any point of sail, for any wind. They will tell you your target speeds, so, for example, if you don't have ideal sails, trim, hull is dirty, or you are towing a bit of weed or something, you can tell by the numbers dropping off.

 

The next step, for offshore races and cruisers, is to add weather routing. This uses the polar files, and the weather forecast, to calculate the best possible route in given weather, for your boat. This feature is almost here in Opencpn as well, just a small bug for the developer to work out.

 

For anyone who is interested in this, and would like to have a play with the polar plugin to begin with, send me a PM with your email add, and I'll send you a copy of the plugin. As I said though, this is NOT READY FOR PUBLIC RELEASE, - it's a beta version, so no guarantee that it will work, or be correct!

 

Finally, who remembers the discussion on here about "Boat Alexander" who was not allowed to leave Opua, and the authorities hauled his boat? The guys name is Sean Depagnier, and he is the programmer writing this stuff!

 

Cheers

Matt

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He went to Vanuatu. After that I don't really know.

Sean is a very gifted guy, and a prolific programmer. I guess he is one of those people who just wants to be left alone to do his thing, and he does not fit into society well. His contribution to opencpn over the last year or so has been HUGE! If he was working for money in the IT industry, he'd be worth a lot. That he is not, is interesting, and fits with what we know of him.

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The cheek of the man, sailing an obviously unsafe boat that looks different from here to Vanuatu then Borneo, after successfully sailing from the US to NZ. Has he no shame?

 

 

Back to the subject - Open CPN is fantastic.

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One of my favourite sailing bloggers is Bob Wise, owner and builder of the original Loose Moose. I tried to find his entry on this but couldn't so will paraphrase as best I can: turning up in an anchorage in a boat so far outside the norm meant we were subject to quite some abuse from people offended by the appearance of our boat. I always considered it a useful "bigot filter" so I'd know who to avoid.

 

 

Apologies for the thread drift.

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Fineline, the weather routing plugin is what I'm working on now. Currently I have been unable to make it work due to a change in the Grib file programming. It DID work, but is currently broken. That is being worked on by the developers now, and should be sorted soon.

If you are interested in it, like the polars, I have the beta versions now... Send me a PM if you'd like a copy, they are not (easily) publicly available yet...

 

OpenCPn Weather Routing.jpg

 

You can see the bit where it says "Grib Failed" in the left hand window. That is the problem. Sean (Boat Alexander) has it working on his "optimized" version of OpenCPN, but it does not yet go in the Stable, or Public Beta versions. Watch this space!!

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Question for you IT... I'm trying out the weather routing plugin in OpenCPN again and I'm getting a "No data: failed" error. I have a a current grib that covers the area and time range that I need a polar file but I can't seem to make it go. Any debugging tips?

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Actually it looks like I was entering the positions in the wrong format so they didn't line up with my grib file. It's off computing a route now... fingers crossed this one works...

 

I managed to get a couple of routes out of it but now I keep getting "Polar failed" even though the polar data I have entered has data right out to 45kts and there is nothing in the grib that exceeds that. I'll keep digging.

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