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distance.h90 @ 10841

Last change on this file since 10841 was 3000, checked in by djlea, 13 years ago
Updated obstools. Addition of headers to programs which explain what each utility does and how to run it. All the programs now build using the naketools utility.
File size: 1.1 KB

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1	REAL FUNCTION distance( plon1, plat1, plon2, plat2 )
2	! Arggumnts
3	REAL :: plon1,plat1,plat2,plon2
4	! Local variables
5	REAL :: zplat1,zplon1,zplat2,zplon2
6	REAL :: za1,za2,zb1,zb2,zc1,zc2,zcos1,zcos2
7	REAL, PARAMETER :: zrad = 3.141592653589793/180.0
8	REAL, parameter :: rearth = 6371229
9
10	zplon1 = plon1
11	zplon2 = plon2
12	IF ( zplon1 < -180 ) zplon1 = zplon1 + 360.0
13	IF ( zplon1 >= 180 ) zplon1 = zplon1 - 360.0
14	IF ( zplon2 < -180 ) zplon2 = zplon2 + 360.0
15	IF ( zplon2 >= 180 ) zplon2 = zplon2 - 360.0
16
17	zplon1 = zplon1 * zrad
18	zplon2 = zplon2 * zrad
19	zplat1 = plat1 * zrad
20	zplat2 = plat2 * zrad
21	zcos1 = COS( zplat1 )
22	zcos2 = COS( zplat2 )
23	za1 = SIN( zplat1 )
24	za2 = SIN( zplat2 )
25	zb1 = zcos1 * COS( zplon1 )
26	zb2 = zcos2 * COS( zplon2 )
27	zc1 = zcos1 * SIN( zplon1 )
28	zc2 = zcos2 * SIN( zplon2 )
29
30	distance = rearth * &
31	& ASIN( SQRT( ABS ( 1.0 - ( za1 * za2 + zb1 * zb2 + zc1 * zc2) ** 2) ) )
32
33	END FUNCTION distance

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