Description Usage Arguments Value Author(s) References See Also Examples

Get the two points where two great cricles cross each other. Great circles are defined by two points on it.

1 | ```
gcIntersect(p1, p2, p3, p4)
``` |

`p1` |
Longitude/latitude of a single point, in degrees; can be a vector of two numbers, a matrix of 2 columns (first one is longitude, second is latitude) or a SpatialPoints* object |

`p2` |
As above |

`p3` |
As above |

`p4` |
As above |

two points for each pair of great circles

Robert Hijmans, based on equations by Ed Williams (see reference)

http://www.edwilliams.org/intersect.htm

1 2 | ```
p1 <- c(5,52); p2 <- c(-120,37); p3 <- c(-60,0); p4 <- c(0,70)
gcIntersect(p1,p2,p3,p4)
``` |

```
Loading required package: sp
lon1 lat1 lon2 lat2
[1,] -21.8096 62.98678 158.1904 -62.98678
```

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