Calibration

Calibrating the wind sensor is a big deal

I’ve talked to a few people “in the industry” and all, to some extent, have asked for software help in calibrating the wind sensor. It makes sense - we bolt these things to the top of the mast then treat their outputs as being accurate to within a degree. Is it really? Has it shifted over the years? And how are we going to find out from within a piece of software?

How to check wind sensor calibration

Let’s start by defining the problem. Imagine our yacht is set up identically on either tack - jib sheeting and cars especially - and is beating to windward. The helm is holding an angle against the (apparent) wind that varies, but averaged across the entire stretch should be identical between tacks. Because it’s an apparent wind, this is independent of any tidal effects.

Now imagine the wind sensor is twisted five degrees to starboard. On the starboard tack we would see the wind angle being reported as five degrees lower on the starboard tack, and five degrees higher on port. This can now be visualised on See Sailing, like this:

The helm’s a bit wobbly (we’re none of us perfect) but we can see that the port tacks are 26 and 24 degrees, and starboard is 34. Assuming the cars and sheets are set up identically we could make an argument for the wind sensor being twisted five degrees to port - causing starboard tacks to read five degrees higher and vice versa.

Now, I know this particular boat and the chances of port and starboard being set up identically are, in this case, kinda small. But it does illustrate the point (and make it clear how important setup is). On the flip side is this recording…

Showing an IMHO terribly broad pointing angle, but that the wind sensor is calibrated accurately. Victory!

Available now

Like everything else being added to See Sailing, this is available now and has been applied to existing recordings in the database - like this one. Go have a look!

Moving forward

From a business perspective, See Sailing has been progressing more slowly. This, sadly, is typical for me - a fundamentally “technical guy” at the best of times. I am, however, making contact with (initially) a few integrators/consultants to discuss both what See Sailing needs to do to become useful as a part of a wider yacht instrumentation solution … and how it may fit with their businesses going forward.

If this is you (or if you’re just interested), have a quick look at this ‘partnering’ page and feel free to get hold of me with comments etc. It’s becoming increasingly clear that this needs to happen for See Sailing to have a future so … if you can think of anyone I should talk to, that also would be really handy.

Next up … video.