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LL_ARC_AZIMUTH_KPB

LL_ARC_AZIMUTH_KPB

Name


LL_ARC_AZIMUTH_KPB

Purpose


This procedure returns the longitudes and latitudes (x1 and y1) of points located at
specified arc distances (arc_dist) and azimuths (az) from a set of initial points (x0 and y0).
By default coordinates are assumed to be in degrees.
This program is based on the IDL library function LL_ARC_DISTANCE, which is
copyright by ITTVIS.

Category


Mapping, geography.

Calling Sequence


LL_ARC_AZIMUTH_KPB, x0, y0, arc_dist, az, x1, y1

Inputs


x0 : longitudes of initial points.
y0 : latitudes of initial points.
arc_dist : arc distances from (x0,y0).
az : azimuths from (x0,y0).

Keyword Parameters


RADIANS : If set, inputs and outputs are in radians, otherwise degrees.

Outputs


x1 : longitudes of final points.
y1 : latitudes of final points.

Procedure


Formula from Map Projections - a working manual. USGS paper
1395. Equations (5-5) and (5-6).

Example


IDL> LL_ARC_AZIMUTH_KPB, 0.0, 30.0, 10.0, 45.0, x1, y1
PRINT, x1, y1
      2.91415
    -0.622235

Modification History


Kenneth P. Bowman, April, 2010. Modified from LL_ARC_DISTANCE to vectorize the calculations.
Note that in this procedure the longitude and latitude are input as two separate arguments,
and the output values are returned through the argument list, rather than via a function call.
Also, for consistency with ARC_AZIMTUH_KPB, angles are assumed to be in degrees, not radians.



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