| 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 | LOGICAL FUNCTION linquad( px, py, pxv, pyv ) |
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| 8 | !!---------------------------------------------------------------------- |
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| 9 | !! *** FUNCTION linquad *** |
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| 10 | !! |
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| 11 | !! ** Purpose : Determine whether a point P(x,y) lies within or on the |
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| 12 | !! boundary of a quadrangle (ABCD) of any shape on a plane. |
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| 13 | !! |
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| 14 | !! ** Method : Check if the vectorial products PA x PC, PB x PA, |
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| 15 | !! PC x PD, and PD x PB are all negative. |
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| 16 | !! |
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| 17 | !! ** Action : |
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| 18 | !! |
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| 19 | !! History : |
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| 20 | !! ! 2001-11 (N. Daget, A. Weaver) |
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| 21 | !! ! 2006-08 (A. Weaver) NEMOVAR migration |
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| 22 | !! ! 2006-10 (A. Weaver) Cleanup |
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| 23 | !!---------------------------------------------------------------------- |
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| 24 | |
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| 25 | !! * Arguments |
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| 26 | REAL(KIND=dp), INTENT(IN) :: px ! (lon) of the point P(x,y) |
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| 27 | REAL(KIND=dp), INTENT(IN) :: py ! (lat) of the point P(x,y) |
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| 28 | REAL(KIND=dp), DIMENSION(4), INTENT(IN) :: pxv, pyv ! (lon, lat) of the surrounding cell |
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| 29 | |
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| 30 | |
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| 31 | |
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| 32 | |
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| 33 | !! * Local declarations |
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| 34 | REAL(KIND=dp) :: zst1 |
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| 35 | REAL(KIND=dp) :: zst2 |
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| 36 | REAL(KIND=dp) :: zst3 |
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| 37 | REAL(KIND=dp) :: zst4 |
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| 38 | |
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| 39 | !----------------------------------------------------------------------- |
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| 40 | ! Test to see if the point is within the cell |
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| 41 | !----------------------------------------------------------------------- |
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| 42 | linquad = .FALSE. |
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| 43 | zst1 = ( px - pxv(1) ) * ( py - pyv(4) ) & |
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| 44 | & - ( py - pyv(1) ) * ( px - pxv(4) ) |
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| 45 | IF ( zst1 <= 0.0 ) THEN |
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| 46 | zst2 = ( px - pxv(4) ) * ( py - pyv(3) ) & |
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| 47 | & - ( py - pyv(4) ) * ( px - pxv(3) ) |
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| 48 | IF ( zst2 <= 0.0 ) THEN |
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| 49 | zst3 = ( px - pxv(3) ) * ( py - pyv(2) ) & |
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| 50 | & - ( py - pyv(3) ) * ( px - pxv(2) ) |
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| 51 | IF ( zst3 <= 0.0) THEN |
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| 52 | zst4 = ( px - pxv(2) ) * ( py - pyv(1) ) & |
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| 53 | & - ( py - pyv(2) ) * ( px - pxv(1) ) |
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| 54 | IF ( zst4 <= 0.0 ) linquad = .TRUE. |
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| 55 | ENDIF |
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| 56 | ENDIF |
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| 57 | ENDIF |
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| 58 | |
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| 59 | END FUNCTION linquad |
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| 60 | |
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