Ever since my adventure at sea, I’ve had a sort of lingering fascination with nautical charts. There’s something imminently … pragmatic about them. I think they’re neat.
In Googling around, I found this NOAA Web site which maintains a huge archive of historical nautical charts. “Historical” is a little bit of a misnomer, I guess, since the charts in the database are as recent as the late 1980s. That makes them utterly useless for navigation, of course, but they’re still really neat to look at.
That’s the good news. The bad news is that the charts are presented in a fairly obscure format called SID. I haven’t the foggiest idea what SID stands for, but I’ve encountered the format once before. High-resolution satellite imagery is sometimes stored in SID format. I worked with it briefly Back In The Day. I had no idea that format was in general use.
So unfortunately you can’t just go to the NOAA Web site and download a big picture and open it up in Preview. You have to jump through a couple of hoops first.
A company unfortunately named LizardTech makes a SID viewer called ExpressView. It’s a spectacularly crappy piece of software, but it’s free and it lets you open SID files and save them in more useful formats, like TIFF. In that way, I was able to download NOAA chart 11463, “Elliott Key to Tarpon Basin,” and snip out this little piece showing Florida’s Cutter Bank.
This snippet comes from a chart of Chesapeake Bay drawn in 1840. Notice the soundings shown for the Potomac River. They’re surprisingly accurate. Modern soundings put the central channel of the Potomac anywhere from twenty to forty feet deep. (I know that because I pulled chart 12289 from 1989 and compared. See how neat this is?)
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