
Check out Will Oxley's new book! Expedition Navigation Software  A Gentle Introduction.
Will provides an expert walkthough on Expedition features for new users and some great tips for everyone. Available now on Amazon for Kindle download. Click Here! 
Offline
This is in the form of a lot of lessons to be learned.
1. Raced our beer can in the "Sweet 16" series of Oakland Yacht Club.
2. Before the start set up Exp with Hlink hoping to log the race.
3. As only 3 aboard a Yawl, we didn't pay any attention to the PC screen through the race,
4. Got a great start, were first at the next two marks, had an over ride on the third leg and let our competition slide by while gybing to clear genoa sheet.
5 held/made up time otherwise,
==> Big help having polars and knowing what the set/rate was to avoid the 1 kt counter current peak.
6 won on corrected.
7. go to review log file, and there's nothing and no track...
8. Assume that I needed to be logging boat zero ? (was unchecked...)
In any case, gave credit to investment in H5000 and Exp...
Offline
Congratulations.
Yes, you need to set it to log boat zero.
Offline
Ok,
my competition is going to be even more intimidated when we get this actually doing something...
related to the TWDPeriod, I am assuming I will get log format that I can manipulate in Excel/JMP ?
I'm going to need to figure out the algorithm to handle the 35901 degree transition,
For what it may be worth, based on sequential readings in Col E, here is the Excel for the signed deltas:
=(IF(ABS($E3$E2)<180,ABS($E3$E2),ABS($E3$E2)360)*IF((E3E2)>0,1,1))
Offline
Wrapping over 0360 has problems from a presentation pov. Most data things are ok as you use components.
I haven't used the fourier at all, but I see it doesn't handle 0360.
Offline
I am playing with that on some shore/buoy data that has longer sample intervals but the concept should be similar. If you do the time series analysis (Fourier Xform) of the (damped?) shifts not the absolute TWD, that might make the math easier. and then for display fit as a discretized overlay to the initial TWD on the wind plot.
You'd then have a contiguous +/ 180 degree extent to calculate on, with more likely a practical +/. 60 degrees if you took perhaps 210 sec average of the TWD for smoothing and calculated the sequential deltas. To some extent a question of how long/large a shift before you'd want to tack on it.
The top image is the direction, the next is the directional shift, third is velocity shift and bottom is the wind speed.
the Spectral density (JMP terms) including the period distribtions.
https://www.facebook.com/photo.php?fbid=10154576546816664&set=a.454010616663.227866.542601663&type=3&theater
I'll hopefully have some log files from this weekend to play with on Monday, with a goal of attempting to figure out what the shift periods are.
Last edited by sheldon.haynie (6/10/2016 7:48 am)
Online!
I'm now intrigued Sheldon, you may be onto something here. WIll watch for the next instalment.
Offline
Had battery issues, so no logs, but researching Von Karman streets, and the Strouhal number as predictions of coastal oscillating shifts, if I can assign a length parameter. https://en.m.wikipedia.org/wiki/Strouhal_number. Would be nice to be able to take grib and process for likely oscillations at forecast speed and wind directions(strategic), as well as to analyze observed shift pattern and predict likely direction and duration(tactical) of next.
Hence other question on race notes, and at some point ability to read position based values from chart/note and use in calculation.
Offline
Since the Low is scrubbing the NBR, here's a bit of distraction for you http://imgur.com/AoVLjNO
won this by 6 minutes even with the lousy tacking angles. (and 1 kt adverse currents from the west)
Online!
Sheldon, WTF is the story with NB? Clearly, divisions started late; clearly the website management isn't quite there .... so what gives?
Offline
Not sure. I watched start of SDL3 as friends are defending on Actaea, a turbo Bermuda40. Supposedly start was later for tide. Read that Wizard and other Gibbs division retired due to 45kt 18 ft forecast. Comanche is going