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### LL_ARC_DISTANCE

LL_ARC_DISTANCE

The LL_ARC_DISTANCE function returns a two-element vector containing the longitude and latitude [lon, lat] of a point given arc distance (-π ≤ Arc_Dist ≤ π), and azimuth (Az), from a specified location Lon_lat0. Values are in radians unless the keyword DEGREES is set.

This routine is written in the IDL language. Its source code can be found in the file ll_arc_distance.pro in the lib subdirectory of the IDL distribution.

## Examples

`; Initial point specified in radians:`
`Lon_lat0 = [1.0, 2.0]`
`; Arc distance in radians:`
`Arc_Dist = 2.0`
`; Azimuth in radians:`
`Az = 1.0`
`Result = LL_ARC_DISTANCE(Lon_lat0, Arc_Dist, Az)`
`PRINT, Result`

IDL prints:

`2.91415   -0.622234`

## Syntax

Result = LL_ARC_DISTANCE( Lon_lat0, Arc_Dist, Az [, /DEGREES] )

## Return Value

Returns a two-element vector containing the point longitude and latitude.

## Arguments

### Lon_lat0

A 2-element vector containing the longitude and latitude of the starting point. Values are assumed to be in radians unless the keyword DEGREES is set.

### Arc_Dist

The arc distance from Lon_lat0. The value must be between -π and +π. To express distances in arc units, divide by the radius of the globe expressed in the original units. For example, if the radius of the earth is 6371 km, divide the distance in km by 6371 to obtain the arc distance.

### Az

The azimuth from Lon_lat0. The value is assumed to be in radians unless the keyword DEGREES is set.

## Keywords

### DEGREES

Set this keyword to express all measurements and results in degrees.

## Version History

 Pre 4.0 Introduced