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