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Navigating with GPS, Charts and Eyeballs
http://www.bvipirate.com/ChartNav.html
This is an excellent page regarding Navigating with GPS, Charts and Eyeballs. It really puts all these issues in prespective. It provides sample charts and photo images. And totally related to practical experience. "A prudent navigator relies on charted latitude/longitude position only on the macro-scale or meso-scale, but not on the micro-scale. That is to say, a good chart can tell you approximately what is at a given latitude/longitude, but not precisely. A good chart also shows the position of smaller details, with the position being accurate relative to other nearby features. To that end, almost all of the current navigation charts, either paper or electronic, work very well. For absolute position (latitude/longitude) they are almost all accurate to within a few hundred yards (meso-scale). For smaller distances (micro-scale), though, you must use relative position and your eyeballs to locate things -- not the charted latitude/longitude." "Rocks and coral and other small details, though, are typically no more than a few feet or tens of feet in size. On a chart, this is micro-detail, and its absolute position has the same inaccuracy as the macro- and meso- data. Many charts simply are not accurate in absolute position down to the scale of tens of feet. However, most charts do have accurate representations of the micro-scale position of features relative to each other and nearby meso-scale features." |
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On Thu, 01 Sep 2005 04:45:53 GMT, (Mic) wrote:
http://www.bvipirate.com/ChartNav.html This is an excellent page regarding Navigating with GPS, Charts and Eyeballs. It really puts all these issues in prespective. It provides sample charts and photo images. And totally related to practical experience. Another good article link: http://www.sailmag.com/features/CT-April05/ Visual navigation - water references Cruising Tips - April 2005 This month: staying out of trouble close to land, tacking tricks, and some anchoring hints |
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