| 1 | !!---------------------------------------------------------------------- |
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| 2 | !! NEMO/OCE 4.0 , NEMO Consortium (2018) |
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| 3 | !! $Id$ |
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| 4 | !! Software governed by the CeCILL license (see ./LICENSE) |
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| 5 | !!---------------------------------------------------------------------- |
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| 6 | |
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| 7 | REAL(KIND=wp) FUNCTION grt_cir_dis( pa1, pa2, pb1, pb2, pc1, pc2 ) |
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| 8 | !!---------------------------------------------------------------------- |
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| 9 | !! *** FUNCTION grt_cir_dis *** |
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| 10 | !! |
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| 11 | !! ** Purpose : Great circle distance between pts (lat1,lon1) |
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| 12 | !! & (lat2,lon2) |
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| 13 | !! |
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| 14 | !! ** Method : Geometry. |
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| 15 | !! |
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| 16 | !! History : |
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| 17 | !! ! 1995-12 (G. Madec, E. Durand, A. Weaver, N. Daget) Original |
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| 18 | !! ! 2006-03 (A. Vidard) Migration to NEMOVAR |
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| 19 | !! ! 2006-10 (A. Weaver) Cleanup |
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| 20 | !!---------------------------------------------------------------------- |
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| 21 | |
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| 22 | !! * Arguments |
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| 23 | REAL(KIND=wp) :: pa1 ! sin(lat1) |
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| 24 | REAL(KIND=wp) :: pa2 ! sin(lat2) |
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| 25 | REAL(KIND=wp) :: pb1 ! cos(lat1) * cos(lon1) |
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| 26 | REAL(KIND=wp) :: pb2 ! cos(lat2) * cos(lon2) |
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| 27 | REAL(KIND=wp) :: pc1 ! cos(lat1) * sin(lon1) |
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| 28 | REAL(KIND=wp) :: pc2 ! cos(lat2) * sin(lon2) |
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| 29 | |
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| 30 | REAL(KIND=wp) :: cosdist ! cosine of great circle distance |
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| 31 | |
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| 32 | ! Compute cosine of great circle distance, constraining it to be between |
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| 33 | ! -1 and 1 (rounding errors can take it slightly outside this range |
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| 34 | cosdist = MAX( MIN( pa1 * pa2 + pb1 * pb2 + pc1 * pc2, 1.0_wp), -1.0_wp ) |
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| 35 | |
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| 36 | grt_cir_dis = & |
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| 37 | & ASIN( SQRT( 1.0_wp - cosdist**2.0_wp ) ) |
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| 38 | |
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| 39 | END FUNCTION grt_cir_dis |
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