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Weather routing with full polaires possible

PostPosted: Thu Dec 13, 2012 7:42 pm
by vendger
Hi Omar,

first of all I would thank you for your wonderful work on the VRTool! As a real-life sailor with a technical / maritime background I'm very excited about the capabilities of this tool and the features especially with respect to weather routing!

While I was first setting up the vrtool I've read most of this forum and the corresponding wiki-pages. Everywhere I've read that due to their high resolution the full polaires from are not supported by the weather routing in vrtool. That's in accordance with what I just read in

Actually I use vrtool with the full polaires (vendeeglobevirtuel_pro-full.csv). I don't experience any problems. My weather routing settings are:
    - isochrone interval 0.1 (larger intervals problematic in terms of calculation time)
    - # of branches 55
    - max. angle to target 160
    - boat wake angle 35
    - iso point spacing 0.1

Omar, can you give me a comment on this? I'm wondering why I can use the full polaires without problems while actually this is not advised. Will the reduced polaires give me more comprehensive results?

Re: Weather routing with full polaires possible

PostPosted: Fri Dec 14, 2012 11:59 am
by omar

I was not able to make it work with the configuration you describe.
The calculation stopped because the number of points (tracks) was too large (over 2 million).

Two important settings are [x] Branch at isochrones and [x] Branch at full degrees
These control in which points a given track forks into multiple tracks.
Branch at full degrees specifies branching when entering a new wind rectangle.
It seems necessary in the constant winds of VR regattas (i.e. you usually have to adjust
the course when entering a new wind rectangle). Branch at isochrones is not
mandatory for VR (except for the wind shift isochrones). But can be used.
You didn't mention how you set these.

In your case, each 6 minutes (0.1 hour), 55 segments are added to each end point.
It is easy to see that the number of tracks will grow very fast. Pruning can keep it in check.
My recommendation not to use full polars was based on guesswork,
not actual experimentation. If it works for you, great.

:arrow: For more WR details read this