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    Re: The magical maths of Google Maps
    From: David Pike
    Date: 2015 Oct 7, 01:31 -0700

    Oh Dear.  You’ll recall that I found the Great Circle from New York to London was 5,577.886km if I used an earth radius of WGS84 a = 6,378,137m.  The geodesic was 5,586.662km using WGS a & b.  I thought it would be easy to check which answer Google Maps gave me, and hence which method Google was using.  Not so!  I converted N50° 30’ W000° 05’ to N50.50000° W0.08333° and N40° 43’ W073° 59’ to N40.71667° W73.98333°.  Then I searched at large scale for the London lat/long.  It came between Learthermarket St and Morocco St Southwark, and I made a sketch of it.  Next I went to the New York lat/long, right clicked, and left clicked “Measure distance”.  I reduced scale, dragged the screen to London, and increased scale until I found Leathermarket St and left clicked the London position.   The first time I tried it I got 5,559.8km.  After breakfast, I tried again and got 5,567.84km, 10km less than my spherical trig value and 19km less than my geodesic value.  So what does this tell us apart from the Earth expands after breakfast?  I dunno.  DaveP

       
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