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SPHIC

SPHIC

## Purpose

Compute intersection points of two circles on a unit sphere.

## Calling Sequence

sphic, ln1,lt1,r1, ln2,lt2,r2, lnp1,ltp1, lnp2,ltp2, flag

## Inputs

ln1 = longitude of circle 1 center. in
lt1 = latitude of circle 1 center. in
r1 = radius of circle 1. in
Angle along sphere surface.
ln2 = longitude of circle 2 center. in
lt2 = latitude of circle 2 center. in
r2 = radius of circle 2. in
Angle along sphere surface.

## Keywords

/DEGREES means all angles are in degrees, else radians.

## Outputs

lnp1 = longitude of intersection 1. out
ltp1 = latitude of intersection 1. out
lnp2 = longitude of intersection 2. out
ltp2 = latitude of intersection 2. out
flag = -2: circles are the same, all points on both.
-1: parallel circles, different radii, no int.
0: non-parallel circles, no intersection.
1: tangent circles, one intersection.
2: circles intersect in two points.

## Notes

Notes: if flag < 1 then returned intersection points
are meaningless and may be undefined.
If flag = 1 then both points are the same.

## Modification History

R. Sterner. 13 Apr, 1988.
R. Sterner. 14 Feb, 1991 --- to IDL V2 & slight changes.
Copyright (C) 1988, Johns Hopkins University/Applied Physics Laboratory
This software may be used, copied, or redistributed as long as it is not
sold and this copyright notice is reproduced on each copy made. This
routine is provided as is without any express or implied warranties
whatsoever. Other limitations apply as described in the file disclaimer.txt.

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