Polar Explorer

I have been intending to write this app for a while now, and with the upcoming IMSYC race on sailonline, with multiple new polars to choose from I though now would probably be a good time to knock it out. It doesn’t include all the features I have planned, but I have changed my original list to accommodate displaying more polars and to support the file format used for the IMSYC boats. It is pretty easy to use, here is a feature list and I will go into some more detail below:

  • Open as many polars as you like, with support for both csv (from brainaid) and SOL txt file formats, correctly handling TWS values in either m/s or kn for the txt files. It should be noted you will bet slightly more accurate display using brainaid’s csv files (as there is more data and pre-interpolated by SOL) but there is no significant difference
  • Display VMG curves on the polar (basically a ‘radial curve’ following the up and downwind vmg TWAs) – This is plotted for every kn of TWS
  • Display VMC curves, for every 15 degrees offset from the wind. So for example the 15 line is for a target 15 degrees from the TWD (toward your sailing angle) – again plotted for every kn TWS
  • Easily set polar windows to the same size for better comparison
  • Colour coding is exactly the same as in SOL client
  • Detailed information at mouse location
  • Drag and Drop support, for both files (ie from a folder displayed in Windows Explorer) and the raw text data (useful when tweaking or for a quick view of the current race polar without a download required). See comment after this post on drag and drop.

OK, now onto some screenshots and more detailed explanation of things.

First, on the File menu there are 2 options:

  1. Open Polar – If there is no polar windows open, this will open a polar in a new window. If however there is a polar window open (or more than 1), it will REPLACE the polar in that window, or whichever is active if there are more than one.
  2. Open Polar in New Window – which is what you will use to open a 2nd and more polar windows for comparison.

When you click either of these when no polar is open, you will be asked to browse for a file. Choose the type you want, wither csv or txt in the browse dialog. When you first open a polar you will see it like this:

You can resize the polar window (and main application of course) to provide a better view of the polar.

Now, on the Display menu are 2 items of much use when comparing polars, even just when studying the one for use in a race. Namely toggle menu items for ‘VMG Lines’ and ‘VMC Lines’ which toggle the display of these on the polar(s) loaded. VMG lines are indicated with a ‘D’ & ‘U’ on them – self-explanatory, and the VMC lines display the degree offset for which they represent the best VMC. You can see both displayed for the Seacart polar below:

Now, as I mentioned you can open more than 1 polar at a time – indeed this is part of the ‘raison d’être’ of the app! (well, of it being released in this form) Just a reminder, if you now use ‘File->Open Polar’ it will REPLACE the polar in the window, you use ‘Open Polar in New Window’ to open another polar window, like so:

As you can see, any display options are also used for newly opened polars. It is more useful to compare polars if they are displayed at the same size, and this can be done with the ‘Display->Same Size’ menu. All open polar windows will be made the same size as the currently active polar (can tell from title bar of the polar window). After clicking this above, you get:

Actually, I also moved the imsyc polar to draw side by side with the Seacart – Display->Same Size only changes the size, not location of the polar windows….

And finally, you can hold the mouse anywhere on a polar to see detailed data, SOG/TWA/VMG, as shown below (although you can’t see the mouse cursor in the pic)

One final note – you may have noticed that the IMSYC polar shown here only displays up to 25 knots TWS. This is because the input polar data is only up to 12 m/s (just under 24 kn) TWS and the interpolant can give some funny results for the 30 knot line, so I decided to leave it out in these instances…

Download from here

The link will take you to the project home page on codeplex, go to the ‘Downloads’ page and click the link under ‘Recommended Downloads’. This will download a small installer that, when run, will download the full application and install it. Once installed there will be a shortcut on the start menu under ‘SOL Tools’.

NOTE: I have now moved this project to the codeplex open source website, to take full advantage of the Microsoft ‘ClickOnce’ deployment technology it uses – this provides you with 2 distinct benefits:

  1. If you run the application while online, it will automatically check for, download and install any future upgrades – with your permission of course.
  2. Being ‘Open Source’ you have full access to the source code  -I know this means little to most, but think of it as an ‘open book’ policy

While I am testing the new deployment method, if for some reason this does not work, use the Contact page and I will provide you with a link to the zip file for interim use.

  1. #1 by ShamrockPirate on May 31, 2011 - 12:32

    AGage… Once again, BRILLIANT STUFF!! I’m not sure exactly how to interpret all the great tools here but it will undoubtedly give me a project to look at. Wish I had more time before the IMSYC. In any event, the tools with VMG/VMC will be a definite help for single-polar races as well. Nicely done!!

    One other thought. If it isn’t already available somewhere, I would LOVE a short treatise on how to best use and understand VMC. For some reason, I still don’t seem to be able to integrate this into my course selection effectively. Perhaps one of the Pros (you, 76T, Schakel, others) might undertake a Blog to help some of us neophytes get a handle on this.
    If it is already described somewhere, just point me in the right direction (much like what VMC is supposed to do anyway :>))).

    Once again, OUTSTANDING work.
    Don’t know how you do it.


  2. #3 by NZL_undercover on June 3, 2011 - 07:43

    Excellent tool mate……well done with all of your fantastic tools. With all this stuff the races should get harder and harder or better and better. 🙂

    • #4 by AGage on June 3, 2011 - 07:59

      I planned a few more features, and hadn’t originally thought of opening as many polars as you like, but got inspired to after the only images of the IMSYC polars were small jpgs or whatever, and not really enough in the pdf’s to tell in detail (some did, some didnt)…
      I do hope using some of this stuff will lift SOL – more or better competition is never a bad thing 😉

  3. #5 by bc on November 11, 2011 - 23:14

    Hi, I’m eager to try this app but every time I try to load a Polar I get an “exception of type ‘alglib_alglibexception’ was thrown” I’m guessing its the format but maybe not. Any thoughts?


  4. #6 by bc on November 11, 2011 - 23:31

    Hold that though, it is definitely the format. I’m sure there is documentation somewhere that tells me how to covert other formats for use here.


    • #7 by AGage on November 12, 2011 - 04:19

      It accepts brainaid’s csv files, or text files like you get from clicking the polar link on the help tab in the client…
      In fact one very easy way to display the polar of the race is to click that polar link, it should open another tab in your browser and display the actual textual data.
      Now, – with Polar Explorer running, highlight ALL of the text and drag it to the Polar Explorer app…
      If it is hidden, drag to the taskbar button and hold for a second, then the PExplorer will pop open on the top of the screen.
      Drag the text onto the app and drop it and a new polar view will open – Viola!

      You can also drag and drop files from Windows Explorer to…


  1. New Tool – Polar Explorer « Sailonline.org Tools
  2. Minor update to Polar Explorer « Sailonline.org Tools

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