### Online geodesic calculations using the GeodSolve utility

Geodesic calculation:
 Inverse: lat1 lon1 lat2 lon2 → azi1 azi2 s12 Direct: lat1 lon1 azi1 s12 → lat2 lon2 azi2

Input (ex. «40.6 -73.8 49°01'N 2°33'E» [inverse], «40d38'23"N 073d46'44"W 53d30' 5850e3» [direct]):

 Output format: Decimal degrees Degrees minutes seconds Heading at point 2: Forward azimuth Back azimuth Output precision: 1m 0.00001d 0.1" 100mm 0.01" 10mm 0.001" 1mm 0.0001" 100um 0.00001" 10um 0.000001" 1um 0.0000001" 100nm 0.00000001" 10nm 0.000000001"

Select action:

Geodesic (input in black, output in blue):

```    status         =
lat1 lon1 faz1 =
lat2 lon2 faz2 =
s12 (m)        = ```

GeodSolve performs geodesic calculations for the WGS84 ellipsoid. The shortest path between two points on the ellipsoid at (lat1, lon1) and (lat2, lon2) is called the geodesic; its length is s12 and the geodesic from point 1 to point 2 has azimuths azi1 and azi2 at the two end points. There are two standard geodesic problems:

• Direct:   given [lat1 lon1 azi1 s12] find [lat2 lon2 azi2];
• Inverse: given [lat1 lon1 lat2 lon2] find [azi1 azi2 s12].
Latitudes and longitudes can be given in various formats, for example (these all refer to the position of Timbuktu):
```        16.776 -3.009
16d47' -3d1'
W3°0'34" N16°46'33"
3:0:34W 16:46:33N```
Azimuths are given in degress clockwise from north. The distance s12 is in meters.

GeodSolve is accurate to about 15 nm and gives solutions for the inverse problem for any pair of points. Many other geodesic calculators (based in Vincenty's method) fail for some inputs; for example, the NGS online inverse geodesic calculator sometimes fails to terminate. (NGS has removed its inverse geodesic calculator in order to address this problem.)

GeodSolve, which is a simple wrapper of the GeographicLib::Geodesic class, is one of the utilities provided with GeographicLib. This web interface illustrates a subset of its capabilities. Geodesics can also be computed using Javascript; see the Javascript geodesic calculator and geodesics on Google maps. If you wish to use GeodSolve directly, download and compile GeographicLib. The algorithms are described in C. F. F. Karney, Algorithms for geodesics, J. Geodesy 87, 43-55 (2013); DOI: 10.1007/s00190-012-0578-z; addenda: geod-addenda.html.

Charles Karney <charles@karney.com> (2013-02-26)