distaz: Distance and Azimuth from two points

Description

Calculate distance, Azimuth and Back-Azimuth from two points on Globe.

Usage

distaz(olat, olon, tlat, tlon)

Arguments

olat

origin latitude, degrees

olon

origin longitude, degrees

tlat

target latitude, degrees

tlon

target longitude, degrees

Value

List:
delDelta, angle in degrees
azAzimuth, angle in degrees
bazback Azimuth, (az+180) in degrees
distdistance in km
err0 or 1, error flag. 0=error, 1=no error, see details

Details

Program is set up for one origin (olat, olon) pair and many target (tlat, tlon) pairs given as vectors.

If multiple olat and olon are given, the program returns a list of outputs for each.

If olat or any tlat is greater than 90 or less than -90 NA is returned and error flag is 0.

If any tlat and tlon is equal to olat and olon, the points are coincident. In that case the distances are set to zero, but the az and baz are NA, and the error flag is set to 0.

Examples

Run this code

####  one point
d = distaz(12, 23, -32,    -65)
d

####  many random target points
org = c(80.222, -100.940)
targ = cbind(runif(10, 10, 50), runif(10, 20, 100))


distaz(org[1], org[2], targ[,1], targ[,2])

############  if origin and target are identical
#####  the distance is zero, but the az and baz are not defined
distaz(80.222, -100.940, 80.222, -100.940)


########################   set one of the targets equal to the origin
targ[7,1] = org[1]
targ[7,2] = org[2]

distaz(org[1], org[2], targ[,1], targ[,2])

####  put in erroneous latitude data

targ[3,1] = -91.3


distaz(org[1], org[2], targ[,1], targ[,2])