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I am having an issue with the accuracy of the formulas for the direct and the inverse problems given at the National Geodetic Survey website. Note: I use the full formulas, including the terms that are otherwise omitted after Eq.(12).

Given a Point A and a point B on the WGS84 ellipsoid, I use the direct problem to get the azimuths and the distance (in my example ~335km).

If I then use the first azimuth and the distance to go from A to B, the new location I obtain is several meters off from B.

This is unacceptable for me, as I am trying to approximate the geodetic line to within a few centimeters.

Are there newer publications that revise Vincenty's formulas and improve on the accuracy?

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  • I ported the NGS FORTRAN to 'C' and Java. I never had accuracy issues. You should check your output against their code.
    – Vince
    Commented Nov 13 at 14:50
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    Consider using geographic lib rather than doing it yourself
    – Ian Turton
    Commented Nov 13 at 17:30
  • @Ian it's in C++, I need to be using pure C. Please let's not devolve in a review of my project requirements.
    – Federico
    Commented Nov 13 at 21:11

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