Frank very good remark!
Almost certainly PL means Polar Latitude that is the angle to the North Earth's Pole (see fig. attached) The value reported differs only by few sec from the value of the complement of the Reduced Latitude. In http://www.gmat.unsw.edu.au/snap/gps/clynch_pdfs/latlons.pdf we read that : <There are two types of latitude The angle that the line makes from the center of the earth is called the geocentric latitude. Geocentric latitude does not strike the surface of the ellipsoid at a right angle. The line perpendicular to the ellipsoid makes an angle with the equatorial plane that is called the geodetic latitude. ("Geodetic" in geodesy usually implies something taken with respect to the ellipsoid.) The latitude on maps is geodetic latitude. > The formulae are : tan(Geoc_Lat)=(1-f) * (1-f) * tan(Geod_Lat) tan(Reduced_Lat)= (1-f) * tan(Geod_Lat) f = 1/298.257 (modern value) , = 1/293.465 (Clarke 1880) With the Clarke value the formula gives : Raduced_Lat =54° 16' 36" and (90-Reduced L.)= 35° 43' 24" Probably in the calculation was used the approximate value f =1/280 , (90° - Red. Lat.) = 35° 43' 40" Best Gianni Ferrari ----- Original Message ----- From: "Frank King" <[EMAIL PROTECTED]> To: "John Foad" <[EMAIL PROTECTED]> Cc: "sundial" <[EMAIL PROTECTED]> Sent: Sunday, April 22, 2007 1:17 PM Subject: Re: strange longitude > Incidentally, this quoted figure for longitude is within > a few arc-minutes of being the co-latitude. Weird! > > Frank King > Cambridge, U.K. > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial >
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