# distaz: Distance and Azimuth from two points In GEOmap: Topographic and Geologic Mapping

## Description

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

## Usage

 `1` ```distaz(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>

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28``` ```#### 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]) ```