## ---- echo=FALSE, include=FALSE-----------------------------------------------
library(knitr)
opts_chunk$set(fig.width = 5, fig.height = 5, fig.cap='',  collapse = TRUE)


## ---- geo3--------------------------------------------------------------------
library(geosphere)
LA <- c(-118.40, 33.95)
NY <- c(-73.78,  40.63)
data(wrld)
plot(wrld, type='l')
gc <- greatCircle(LA, NY)
lines(gc, lwd=2, col='blue')
gci <- gcIntermediate(LA, NY)
lines(gci, lwd=4, col='green')
points(rbind(LA, NY), col='red', pch=20, cex=2)
mp <- midPoint(LA, NY)
onGreatCircle(LA,NY, rbind(mp,c(0,0)))
points(mp, pch='*', cex=3, col='orange')
greatCircleBearing(LA, brng=270, n=10)


## ---- geo7--------------------------------------------------------------------
ml <- gcMaxLat(LA, NY)
lat0 <- gcLat(LA, NY, lon=0)
lon0 <- gcLon(LA, NY, lat=0)
plot(wrld, type='l')
lines(gc, lwd=2, col='blue')
points(ml, col='red', pch=20, cex=2)
points(cbind(0, lat0), pch=20, cex=2, col='yellow') 
points(t(rbind(lon0, 0)), pch=20, cex=2, col='green' )

f <- function(lon){gcLat(LA, NY, lon)}
opt <- optimize(f, interval=c(-180, 180), maximum=TRUE)
points(opt$maximum, opt$objective, pch=20, cex=2, col='dark green' )
anti <- antipode(c(opt$maximum, opt$objective)) 
points(anti, pch=20, cex=2, col='dark blue' )


## ---- geo9--------------------------------------------------------------------
SF <- c(-122.44, 37.74)
AM <- c(4.75, 52.31)
gc2 <- greatCircle(AM, SF)
plot(wrld, type='l')
lines(gc, lwd=2, col='blue')
lines(gc2, lwd=2, col='green')
int <- gcIntersect(LA, NY, SF, AM)
int
antipodal(int[,1:2], int[,3:4])
points(rbind(int[,1:2], int[,3:4]), col='red', pch=20, cex=2)
bearing1 <- bearing(LA, NY)
bearing2 <- bearing(SF, AM)
bearing1
bearing2
gcIntersectBearing(LA, bearing1, SF, bearing2)