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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Further on Datum Shifts From Bowditch
From: John Kabel
Date: 2002 Jan 18, 7:04 AM
From: John Kabel
Date: 2002 Jan 18, 7:04 AM
In the 1995 Bowditch, section 211, it says, referring to the replotting of positions from one chart to another, with a datum change: "These datum shifts are not constant throughout a given area, but vary according to how the differing datums fit together. For example, the NAD27 to NAD 83 conversion results in changes in latitude of 40 meters in Miami, 11 meters in New Yourk, and 20 meters in Seattle. Longitude changes for this conversion are about 22 meters in Miami, 35 meters in New York, and 93 meters in Seattle." There is no mention of a "1 mile" datum shift between NAD 27 and NAD 83. That would be very surprising if it were true, as the only shift of that magnitude I am aware of is the NAD 27 to TOKYO datum shift. John Kabel In around 43 N, 81 W London, Ontario
