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
Lon_lat0 = [1.0, 2.0]
Arc_Dist = 2.0
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
See Also