# st: ST: vincenty formula for Africa

 From Laura Platchkov <[email protected]> To "[email protected]" <[email protected]> Subject st: ST: vincenty formula for Africa Date Sun, 13 Sep 2009 13:22:06 +0100

```Dear all,

I am trying to find out abotu those distances, and apparently somethign went wrong with the conversion and the distmatch formula, so I am thinkin abotu trying the vincenty.

I am not experienced wiht programming,... may I ask if someone knows  how to modify the vincenty command for Africa, using Clarke 1880 ellipsoid value?

From:http://www.movable-type.co.uk/scripts/latlong-vincenty.html

The most accurate and widely used globally-applicable model for the earth ellipsoid is WGS-84, used in this script. Other ellipsoids offering a better fit to the local geoid include Airy (1830) in the UK, International 1924 in much of Europe, Clarke (1880) in Africa, and GRS-67 in South America. America (NAD83) and Australia (GDA) use GRS-80, functionally equivalent to the WGS-84 ellipsoid.
WGS-84 	a = 6 378 137 m (±2 m) 	b = 6 356 752.3142 m 	f = 1 / 298.257223563
GRS-80 	a = 6 378 137 m 	b = 6 356 752.3141 m 	f = 1 / 298.257222101
Airy (1830) 	a = 6 377 563.396 m 	b = 6 356 256.909 m 	f = 1 / 299.3249646
Int?l 1924 	a = 6 378 388 m 	b = 6 356 911.946 m 	f = 1 / 297
Clarke (1880) 	a = 6 378 249.145 m 	b = 6 356 514.86955 m 	f = 1 / 293.465

Laura

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