R: Distance and Azimuth from two points

rdistaz {RSEIS} | R Documentation

## Distance and Azimuth from two points

### Description

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

### Usage

    rdistaz(olat, olon, tlat, tlon)

### Arguments

`olat` | origin latitude, degrees
`olon` | origin longitude, degrees
`tlat` | target latitude, degrees
`tlon` | target longitude, degrees

### 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.

### Value

List:

`del` | Delta, angle in degrees
`az` | Azimuth, angle in degrees
`baz` | Back-Azimuth, (az+180) in degrees
`dist` | Distance in km
`err` | 0 or 1, error flag. 0=error, 1=no error, see details

### Author(s)

Jonathan M. Lees<jonathan.lees@unc.edu>

### See Also

along.great, getgreatarc

### Examples

    ####  one point
    d <- rdistaz(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))

    rdistaz(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
    rdistaz(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]

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

    ####  put in erroneous latitude data

    targ[3,1] <-  -91.3

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

[Package RSEIS version 3.7-4 Index]