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


## ---- geo1--------------------------------------------------------------------
library(geosphere)
Lon = c(1:9/1000, 1:9/100, 1:9/10, 1:90*2) 
Lat = c(1:9/1000, 1:9/100, 1:9/10, 1:90) 
dcos = distCosine(c(0,0), cbind(Lon, Lat))
dhav = distHaversine(c(0,0), cbind(Lon, Lat))
dvsp = distVincentySphere(c(0,0), cbind(Lon, Lat))
par(mfrow=(c(1,2)))
plot(log(dcos), dcos-dhav, col='red', ylim=c(-1e-05, 1e-05), 
            xlab="Log 'Law of Cosines' distance (m)", 
            ylab="Law of Cosines minus Haversine distance")
plot(log(dhav), dhav-dvsp, col='blue',
            xlab="Log 'Haversine' distance (m)", 
            ylab="Vincenty Sphere minus Haversine distance")


## ---- geo2--------------------------------------------------------------------
dvse = distVincentyEllipsoid(c(0,0), cbind(Lon, Lat))
plot(dvsp/1000, (dvsp-dvse)/1000, col='blue', xlab='Vincenty Sphere Distance (km)', 
        ylab="Difference between 'Vincenty Sphere' and 'Vincenty Ellipsoid' methods (km)")


## ---- geo14-------------------------------------------------------------------
line <- rbind(c(-180,-20), c(-150,-10), c(-140,55), c(10, 0), c(-140,-60))
pnts <- rbind(c(-170,0), c(-75,0), c(-70,-10), c(-80,20), c(-100,-50),
           c(-100,-60), c(-100,-40), c(-100,-20), c(-100,-10), c(-100,0))
d = dist2Line(pnts, line)
plot( makeLine(line), type='l')
points(line)
points(pnts, col='blue', pch=20)
points(d[,2], d[,3], col='red', pch='x', cex=2)
for (i in 1:nrow(d)) lines(gcIntermediate(pnts[i,], d[i,2:3], 10), lwd=2, col='green')