Next message: Ken Gebhart: "Re: Oceanic Ferrying- was Sun squash"
For those of us lucky enough to be on the west coast, the January
edition of "Latitude 38" in the column "Max Ebb: photo finish", p.p.
158 - 161 is of interest.
The gist of the article was that on a race to Mexico the Navigator
forgot his sextant. He determined his position using photoshop and a
digital camera.
He measured the number of pixels that told him the angle. He knew the
focal length of the lens, the size of the sensor in the camera and the
number of pixels across the image.
Using photoshop he determined the sun to be 303 pixels wide at the zoom
setting.
He then checked the Nautical Almanac data: Semi-diameter of the sun is
16.3 minutes at that time of year which came out to 0.176 minutes per
pixel.
He then measured the distance from the top edge of the sun to the
horizon; checked the line length and divided by 60 and he got the
"observed altitude" of the sun's upper limb in degrees.
He then checked the clock time of the camera with the GPS time for the
chronometer correction and used the PC-Nav DOS program from Davis and
cranked out the program.
He got the longitude position that was within 0.4 miles.
Frank Swift
KG6WZA S/V "Is A Bella"
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~ _) ~ The world is not interested in how many storms you survived,
only that the ship arrived. ~ _) ~
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