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Old 11-09-2010, 02:32   #16
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Thomas: I just saw that the South Atlantic pilot charts are available on the NGA site.
Thanks dpons.
You're right. Even the North Pacific Pilot Charts are now available.
Looks like I have some work to do this weekend
Thomas
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Old 11-09-2010, 03:06   #17
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What exactly is involved in converting them, is there no way to automate the process, ie upload pdf, get back chart
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Old 11-09-2010, 03:45   #18
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What exactly is involved in converting them, is there no way to automate the process, ie upload pdf, get back chart
No secrets at all. I have already "published" all steps involved, except for splitting the NA & SP pdfs to individual pdf files. All steps are scripted, except for the initial compromise when it comes to size/resolution used, after that, yes it could all be glued together, ...
But, there is a "but", the individual monthly pictures are not identical when it comes to geo referencing. For example The Cape of Good Hope is not on the same pixels in the Jan sheet as in the Sept sheet and so on. So in the end I have to adjust the tif2bsb header(template) file for each month, manually, by checking them in Gimp. This is also necessary because of a "hack" to force OpenCPN to display the monthly charts in the right order.

Thomas
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Old 11-09-2010, 05:04   #19
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Thanks Thomas, now that you mention it I think I actual saw the link a few days ago, lol, pity about having to fix the pixel alignment
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Old 11-09-2010, 05:26   #20
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Thanks Thomas, now that you mention it I think I actual saw the link a few days ago, lol, pity about having to fix the pixel alignment
I even had to a deal with the fact that every monthly picture has different a size, and is skewed.... But that is OK, it's a one time effort, hopefully

Uploading SA now, about 5 min to go. Link already on the download page. North Pacific next......

Thomas
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Old 11-09-2010, 06:44   #21
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No problem Sea Life is a lucky yacht, isn't she ?

This leads to the question when and how you use pilot charts.
If you are looking for reliable statistics when it comes to winds there is no better source than COGOW Climatology of Global Ocean Winds - COGOW. This is based on data collected by Quick Scat, during it's total operational time. This is the best up to-date information, including the weather patterns during the last ~10 years, and observations covers all areas, not just ship reports. Maybe some day COGOW will be available as a KML overlay of OpenCPN or as vector chart.
The pilot charts, of course contains much more than wind data, and ... are now available directly in your normal chart plotter, but the data is slightly dated.

Neither COGOW nor Pilot Charts says anything about the wind you actually will experience on a given crossing, but if you ever do a specific crossing multiple times, your average will be close to what is stated in the pilot chart.

Pilot charts are for planning long term, think seasons. Weather forecasts are for the short term decisions. </rambling>

Thomas
What a brilliant site ! I had never even heard of it before. It's much more user friendly than the Pilot Charts.
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Old 11-09-2010, 14:29   #22
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The North Pacific Pilot Charts are ready for download. Don't blame me for the extra "features" on for example the Nov chart (SE corner).
For good measure there is also a Magnetic Variation chart from "Epoch 2000" to download, split in three overlapping parts. This works nicely with quilting.

Thomas
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