Boat Length and Bow Offset

In 1.67 version of the watch app I could not find how to set the Boat Length and Bow Offset. Has this option been removed in this version?

Topic

[Alan Smith]

No, it was never there! We haven’t yet built the facility to set the boat length or bow offset. You are stuck with a 40 ft yacht  with a bowoffset of 8 metres It does detract from the precision of the Perfect Start, but we’re sure you will bear with us until we implement some user input to the settings page where you’ll be able to tweak lots of parameters.

[Pieter Oskam]

According to my tests, boat offset is not taking into account when calculating distance to line. So basically what I do is when setting up the “perfect start” is to ping the RCB location when the bow of my boat is at the RCB. Sames goed for the Pin-end. Ping the mark when the bow is at the Pin-End.

I have a bow-offset of 12ft/3.5 meters. Since I start 45 degrees angle to the wind, the true offset would be COS(45)*3.5=2.5 meters

Don’t make it complicated, just ping the marks with the tip of your bow. The GPS is far to slow to really have a precise reading during the last 10 seconds of the start. I only use it between 60 seconds and 15 seconds to start when we are actually floating on the same spot.

[Alan Smith]

You are awesome! Absolutely correct, ping the line does not take into account the bow offset. That’s a failure of documentation. To ping the ends of the line you should align the mark as close to the phone’s GPS location as possible.

I decided not to use bow offset for pinging the line (or the marks) as I couldn’t be sure from which direction you would be approaching the line end, sometimes you’ll run the line, sometimes approach the end from downwind, so I took the approach to use no offset. This is also true for pinging parks of the course.

But the bow offset IS used for the Distance to Line (DTL) and assumes you’re approaching the line at 45 degrees, using the cosine rule you noted.

[Pieter Oskam]

Alan, though you say that a bowoffset of 8 meters is taking into account, my test proves otherwise.

I have made a video of pebble test. In this video you see that no bow-offset is into account.

[Alan Smith]

Hi Pieter,

Brilliant work! I have similarly spent many hours pacing around a playing field just like that.

I saw your evidence about not using bow-offset at the start, and it surprises me, as it is coded to do that and it does for me!  I’ll have to do some more work to see what’s happening.

Regarding no layline alert for the top mark: you were assuming that it would automatically start navigating to the top mark after rounding the bottom mark. A very good assumption, but unfortunately not one that I have incorporated in the code. It didn’t report the layline because you hadn’t explicitly told it it to navigate back to the top mark. You have to go to the mark menu screen and select the mark to navigate to in order to get it layline alerts. A good thought for an enhancement.

Your comments about how long it takes to report tack analysis and mark creation are fair while pacing round a field, but it has to find you on a new stable course before it can determine you’ve tacked or rounded a mark. For that it needs at least 30 seconds of data on the new course before it can determine that it is a new stable course.

 

 

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