Intersections of two great circles
Get the two points where two great cricles cross each other. Great circles are defined by two points on it.
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)
p1 <- c(5,52); p2 <- c(-120,37); p3 <- c(-60,0); p4 <- c(0,70) gcIntersect(p1,p2,p3,p4)
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