Position Ambiguity [was] Re: [aprssig] findu.com....

KC2MMI (Jared) kc2mmi at verizon.net
Tue Jun 13 12:13:48 CDT 2006


"  >That said, the disclaimer that you see on your eTrex seems to
>apply  to air navigation
Rather to marine navigation, but it's the same type of warning :-) "

Historical side note: one of the reasons that marine chart reproductions carried
those warnings, was because they were normally simple photographs of the actual
government charts. In process photography, there is usually some keystone
distortion in the camera which changes a "square" original into a trapezoidal
final image. (Or worse, if the camera is out of alignment in two dimensions.)

So there was good reason to issue that warning on the chart reproductions, as
you could almost guarantee they would introduce some distortion into the charts.
(Along with a tremendous price reduction, to be fair.)

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