Impossible

Based on the Pilot Charts, it is impossible to have calms or south wind where we are, absolutely impossible.
But that is what we had last night, though...

http://donpedro.lediouris.net/voyage/locator/locator.html?latitude=27.345666666666666&longitude=-129.23583333333335&scale=14&currentdate=8%20Oct%202010%2C%2009%3A14%20PDT%20%28GMT%20-0700%29%3Cbr%3EHDG%3A182%2C%20Speed%3A04.02%20kts%3Cbr%3EWind%3A%20Force%202-3%2C%20E%3Cbr%3EApproaching%20the%20Trade%20Wind...

D'apres les Pilot Charts, il est impossible d'avoir du calme ou du vent de sud la ou nous sommes, categoriquement. Mais c'est pourtant bien ce qu'on a eu cette nuit.

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One night with no wind/Une nuit sans vent

We've been stuck - almost - all night in no wind. The north wind died with the day.
We hope the the trade wind will show up soon.

http://donpedro.lediouris.net/voyage/locator/locator.html?latitude=28.818&longitude=-128.703&scale=5&currentdate=7%20Oct%202010%2C%2007%3A40%20PDT%20%28GMT%20-0700%29%3Cbr%3EHDG%3A198%2C%20Speed%3A04.10%20kts%3Cbr%3EWind%3A02.53%20kts%2C%2050%3Cbr%3EWind%3A%20Force%201%2C%20NE%3Cbr%3EPetole%21

On a ete empetole toute la nuit, le vent de Nord est mort avec le jour.
On espere que l'alize va se montrer bientot.

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Flying fish/poisson volant

On a eu le premier poisson volant ce matin, il a aterri sur la figure a Corine pendant qu'elle dormait sur le pont.

http://donpedro.lediouris.net/voyage/locator/locator.html?latitude=29.756833333333333&longitude=-128.307&scale=5&currentdate=6%20Oct%202010%2C%2014%3A26%20PDT%20%28GMT%20-0700%29%3Cbr%3EHDG%3A198%3Cbr%3ESpeed%3A05.37%20kts%3Cbr%3EFlying%20fish%20on%20the%20deck

We've got our first flying fish this morning, it landed in Corine's face when she was napping on the deck.

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Windy!

Voila deux jours qu;on est dans un flux de N de 20 a 25 noeuds.
On porte yankee, trinquette et deux ris dans la grand voile.
Il y a une bonne houle d'ouest.
Tout va bien a bord!

http://donpedro.lediouris.net/voyage/locator/locator.html?latitude=31.263166666666667&longitude=-127.61283333333333&scale=5&currentdate=5%20Oct%202010%2C%2021%3A15%20PDT%20%28GMT%20-0700%29%3Cbr%3EHDG%3A192%3Cbr%3ESpeed%3A06.41%20kts%3Cbr%3E%3Cbr%3EWindy%21

We've been in the past two days in a North flow of 20 to 25 knots.
We carry yankee, staysail and two reefs in the main.
Big swell from west.
All is Ok!

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Sortis des nuages/Out of te clouds

Le ciel s'est degage cette nuit, on est en route sous yankee, trinquette et grand voile haute.
Tout le monde est en forme.

http://donpedro.lediouris.net/voyage/locator/locator.html?latitude=34.11483333333333&longitude=-125.949&scale=5&currentdate=4%20Oct%202010%2C%2014%3A52%20PDT%20%28GMT%20-0700%29%3Cbr%3EHDG%3A205%3Cbr%3ESpeed%3A06.58%20kts%3Cbr%3ETout%20le%20monde%20est%20en%20forme%2C%20one%20est%20sorti%20des%20nuages.

The sky cleared up last night, we carry yankee, staysail and full main.
Everyone is in good shape.

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first night / premiere nuit

Tout va bien, on a eu une premiere nuit rapide, tout dessus.
Avec marsouins, baleines, et dauphins ce matin!

http://donpedro.lediouris.net/voyage/locator/locator.html?latitude=36.677166666666665&longitude=-123.96616666666667&scale=10&currentdate=3%20Oct%202010%2C%2007%3A56%20PDT%20%28GMT%20-0700%29%3Cbr%3E%3Cbr%3EHDG%3A210%3Cbr%3ESpeed%3A04.57%20kts%3Cbr%3E%3Cbr%3EAll%20good%21

All is OK, we had a first fast night, all sails out.
With porpoises, whales, and dolphins this morning!

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Mercator Scale

There are two schools - at least - to plot a line of position with enough details.
Mercator templates are one, plotting sheets are another one.
The plotting sheets rely on the Mercator scale, available at the bottom right corner of the document above. It gives graphically the ratio between one degree of latitude and one degree of longitude.
The Mercator projection relies on the concept of "Increasing Latitude", that gives the value of the latitude, in degrees of longitude...
The increasing latitude λ, for a latitude φ is given by the following formula:

λ(φ) = ln(tan(π/4 + φ/2))

The Mercator scale gives the the ratio between one degree of latitude and one degree of increasing latitude at the given latitude. In consequence, its formula is

ratio = (φ - (φ - 1)) / (λ(φ) - λ(φ - 1))

simplified as

ratio = 1 / (λ(φ) - λ(φ - 1))

also written

ratio = (λ(φ) - λ(φ - 1))^-1

That's it!
The main difference I can see between the two methods is that the Mercator templates can be reused, just like a chart, and the plotting sheets are just a draft, to be dropped after used. That's just my opinion. Whoever has a better - or other - one is welcome to speak up.

True Wind calculation, SOG+COG vs BSP+HDG

It is a commonly admitted fact that you should calculate the true wind with the apparent wind speed and angle (a vector), to which you add the vector of the boat speed and heading.
The trick is that the boat speed and heading should not be the one taken on the water, but on the ground. That means that you need COG & SOG coming from the GPS, and not the Boat SPeed and HeaDinG returned by the instruments (like speedometer and compass).
Imagine that:
You are sailing is absolutely NO wind at all, and you have a current of 3 knots, taking you to the 270° true. The apparent wind you feel comes from the 270° true, at 3 knots. We assume that your boat speed - returned by the speedometer - is 0 knots, and we just don't care about the heading.
If you combine this apparent wind vector with the data returned by the GPS (COG=270°, SOG=3), than you appropriately find that the TWS is zero, as it actually is.
But if you use the Boat Speed returned by the speedometer, then you find a TWS of 3 knots, which is absolutely wrong!
I believe most of the stations computing the True Wind for you are in fact using the data coming from the instruments (and not the GPS). I need to check that..., but is that is the case, then there is a problem.

Routing Slicing

Just like we had a GRIB Slicing feature, you can now visualize the conditions at the routing level.

Drag the mouse on the top pane, and that tells you where you are on the chart, with a big red dot.

Beside that, it was so windy today in Oyster Point that the wind blew my glasses off my nose... I just could see them sinking 30 feet away from the dock. Rats!

Dynamic Java compilation, from a String

Kind of out the the scope of this blog, but as it made me sweat, it might be interesting for some people... The main goal was initially to be able to dynamically override a method of some (Java) class, compile and run it.

I used it for Unit Testing (JUnit), to have the setUp() method of some generic test object to initialize some System variables, context dependent (defined by some properties file).
It's about being able to dynamically generate the code to compile into a String (or StringBuffer, or byte array, or whatever...), compile, load and run it. It is not as trivial as it sounds.
Here is the code I used.

And it is possible not to write the class on the file system. Everything happens in memory.