What is northern most point that will be reached when following a great circle? Computed with Clairaut's formula. The southern most point is the antipode of the northern-most point. This does not seem to be very precise; and you could use optimization instead to find this point (see examples)
Usage
gcMaxLat(p1, p2)
Arguments
p1
longitude/latitude of point(s). Can be a vector of two numbers, a matrix of 2 columns (first one is longitude, second is latitude) or a SpatialPoints* object
# NOT RUN {gcMaxLat(c(5,52), c(-120,37))
# Another way to get there:f <- function(lon){gcLat(c(5,52), c(-120,37), lon)}
optimize(f, interval=c(-180, 180), maximum=TRUE)
# }