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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Equal altitudes and double altitudes.
From: Fred Hebard
Date: 2010 Jun 13, 09:18 -0400
From: Fred Hebard
Date: 2010 Jun 13, 09:18 -0400
I believe deflection of the vertical was first discovered by hydrographic surveyors along the western coast of South America, where the Andes reach almost to the ocean. Of course people working in the Alps or India also may noticed it. On Jun 13, 2010, at 1:29 AM, Paul Hirose wrote: > Of course an astrolabe is affected by deflection of the vertical, > so its > latitudes and longitudes are a little different from the "geodetic" > values shown on a map or GPS receiver. This is true of all instruments > that rely on gravity. Deflection of the vertical is usually a few > seconds of arc, but sometimes tens of seconds. In the mountains above > the Los Angeles basin, at the Mount Wilson Observatory, it's nearly > 30".
