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There are several algorithms to calculate distance between two latitude/longitude points.

  1. Haversine
  2. Hubeny
  3. Lambert-Andoyer
  4. Vincenty's formulae for inverse problem

But there are not so many algorithms (actually I can't finally find it) which can calculate latitude/longitude of point B from another latitude/longitude point A with bearing and distance.

  1. Vincenty's formulae for direct problem

I'm glad to know if there are any algorithms which is lesser accurate, but faster than Vincenty's formulae.

Izumi Kawashima
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2 Answers2

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How about a method which is both more accurate and faster? This is provided by GeographicLib. Comparative timings (C++ implementations on a 2.66GHz Intel processor, using g++) are:

Vincenty direct:                          1.11 us
GeographicLib::Geodesic::Direct:          0.88 us
GeographicLib::GeodesicLine::Position:    0.37 us
GeographicLib::GeodesicLine::ArcPosition: 0.31 us

The accuracy of Vincenty's formulas is about 0.1 mm, while the accuracy of the GeographicLib algorithms about 0.01 um. Geodesic::Direct does a straight solution of the direct problem. It's somewhat faster than Vincenty because it's non-iterative and because it uses Clenshaw summation to evaluate the trigonometric series. GeodesicLine::Position allows you to calculate many points along a single geodesic about 2.4 times faster. If you merely want some points on a geodesic which are approximately equally spaced (e.g., for plotting it), you can use GeodesicLine::ArcPosition and shave a little extra time off the computation. You can reduce the time still further by reducing the order of the series used by GeographicLib from 6 to 3 by compiling with

-DGEOGRAPHICLIB_GEODESIC_ORDER=3

The accuracy is then 0.04 mm, i.e., comparable to, but slightly better than, Vincenty.

A cookbook recipe for solving the equivalent problem on a sphere is given by the Wikipedia entry on great-circle navigation.

cffk
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Here is a link to some code that will do what you are looking for, but will require a bit of work to use:

Inverse and Forward Azimuth Algorithms

The source code is in Fortran so you will have to convert it to the format of your choice. I have used these algorithms in the past without any problems but you will need to test them to determine if they are accurate enough for your needs.

dblanchett
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