| 1 | LOGICAL FUNCTION linquad( px, py, pxv, pyv ) |
|---|
| 2 | !!---------------------------------------------------------------------- |
|---|
| 3 | !! *** FUNCTION linquad *** |
|---|
| 4 | !! |
|---|
| 5 | !! ** Purpose : Determine whether a point P(x,y) lies within or on the |
|---|
| 6 | !! boundary of a quadrangle (ABCD) of any shape on a plane. |
|---|
| 7 | !! |
|---|
| 8 | !! ** Method : Check if the vectorial products PA x PC, PB x PA, |
|---|
| 9 | !! PC x PD, and PD x PB are all negative. |
|---|
| 10 | !! |
|---|
| 11 | !! ** Action : |
|---|
| 12 | !! |
|---|
| 13 | !! History : |
|---|
| 14 | !! ! 2001-11 (N. Daget, A. Weaver) |
|---|
| 15 | !! ! 2006-08 (A. Weaver) NEMOVAR migration |
|---|
| 16 | !! ! 2006-10 (A. Weaver) Cleanup |
|---|
| 17 | !!---------------------------------------------------------------------- |
|---|
| 18 | |
|---|
| 19 | !! * Arguments |
|---|
| 20 | REAL(KIND=wp), INTENT(IN) :: px ! (lon) of the point P(x,y) |
|---|
| 21 | REAL(KIND=wp), INTENT(IN) :: py ! (lat) of the point P(x,y) |
|---|
| 22 | REAL(KIND=wp), DIMENSION(4), INTENT(IN) :: & |
|---|
| 23 | & pxv, & ! (lon, lat) of the surrounding cell |
|---|
| 24 | & pyv |
|---|
| 25 | |
|---|
| 26 | !! * Local declarations |
|---|
| 27 | REAL(KIND=wp) :: zst1 |
|---|
| 28 | REAL(KIND=wp) :: zst2 |
|---|
| 29 | REAL(KIND=wp) :: zst3 |
|---|
| 30 | REAL(KIND=wp) :: zst4 |
|---|
| 31 | |
|---|
| 32 | !----------------------------------------------------------------------- |
|---|
| 33 | ! Test to see if the point is within the cell |
|---|
| 34 | !----------------------------------------------------------------------- |
|---|
| 35 | linquad = .FALSE. |
|---|
| 36 | zst1 = ( px - pxv(1) ) * ( py - pyv(4) ) & |
|---|
| 37 | & - ( py - pyv(1) ) * ( px - pxv(4) ) |
|---|
| 38 | IF ( zst1 <= 0.0 ) THEN |
|---|
| 39 | zst2 = ( px - pxv(4) ) * ( py - pyv(3) ) & |
|---|
| 40 | & - ( py - pyv(4) ) * ( px - pxv(3) ) |
|---|
| 41 | IF ( zst2 <= 0.0 ) THEN |
|---|
| 42 | zst3 = ( px - pxv(3) ) * ( py - pyv(2) ) & |
|---|
| 43 | & - ( py - pyv(3) ) * ( px - pxv(2) ) |
|---|
| 44 | IF ( zst3 <= 0.0) THEN |
|---|
| 45 | zst4 = ( px - pxv(2) ) * ( py - pyv(1) ) & |
|---|
| 46 | & - ( py - pyv(2) ) * ( px - pxv(1) ) |
|---|
| 47 | IF ( zst4 <= 0.0 ) linquad = .TRUE. |
|---|
| 48 | ENDIF |
|---|
| 49 | ENDIF |
|---|
| 50 | ENDIF |
|---|
| 51 | |
|---|
| 52 | END FUNCTION linquad |
|---|
| 53 | |
|---|
