[92fab65] | 1 | ! SPDX-FileCopyrightText: FLEXPART 1998-2019, see flexpart_license.txt |
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| 2 | ! SPDX-License-Identifier: GPL-3.0-or-later |
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[332fbbd] | 3 | |
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[e200b7a] | 4 | !----------------------------------------------------------------------- |
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| 5 | function distance2(rlat1,rlon1,rlat2,rlon2) |
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| 6 | |
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| 7 | !$$$ SUBPROGRAM DOCUMENTATION BLOCK |
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| 8 | ! |
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| 9 | ! SUBPROGRAM: GCDIST COMPUTE GREAT CIRCLE DISTANCE |
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| 10 | ! PRGMMR: IREDELL ORG: W/NMC23 DATE: 96-04-10 |
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| 11 | ! |
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| 12 | ! ABSTRACT: THIS SUBPROGRAM COMPUTES GREAT CIRCLE DISTANCE |
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| 13 | ! BETWEEN TWO POINTS ON THE EARTH. COORDINATES ARE GIVEN IN RADIANS! |
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| 14 | ! |
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| 15 | ! PROGRAM HISTORY LOG: |
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| 16 | ! 96-04-10 IREDELL |
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| 17 | ! |
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| 18 | ! USAGE: ...GCDIST(RLAT1,RLON1,RLAT2,RLON2) |
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| 19 | ! |
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| 20 | ! INPUT ARGUMENT LIST: |
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| 21 | !rlat1 - REAL LATITUDE OF POINT 1 IN RADIANS |
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| 22 | !rlon1 - REAL LONGITUDE OF POINT 1 IN RADIANS |
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| 23 | !rlat2 - REAL LATITUDE OF POINT 2 IN RADIANS |
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| 24 | !rlon2 - REAL LONGITUDE OF POINT 2 IN RADIANS |
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| 25 | ! |
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| 26 | ! OUTPUT ARGUMENT LIST: |
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| 27 | !distance2 - REAL GREAT CIRCLE DISTANCE IN KM |
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| 28 | ! |
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| 29 | ! ATTRIBUTES: |
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| 30 | ! LANGUAGE: Fortran 90 |
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| 31 | ! |
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| 32 | !$$$ |
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| 33 | |
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| 34 | use par_mod, only: dp |
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| 35 | |
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| 36 | implicit none |
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| 37 | |
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| 38 | real :: rlat1,rlon1,rlat2,rlon2,distance2 |
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| 39 | real(kind=dp) :: clat1,clat2,slat1,slat2,cdlon,crd |
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| 40 | real(kind=dp),parameter :: rerth=6.3712e6_dp |
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| 41 | real(kind=dp),parameter :: pi=3.14159265358979_dp |
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| 42 | |
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| 43 | if ((abs(rlat1-rlat2).lt.0.0003).and. & |
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| 44 | (abs(rlon1-rlon2).lt.0.0003)) then |
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| 45 | distance2=0.0_dp |
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| 46 | else |
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| 47 | |
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| 48 | ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - |
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| 49 | clat1=cos(real(rlat1,kind=dp)) |
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| 50 | slat1=sin(real(rlat1,kind=dp)) |
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| 51 | clat2=cos(real(rlat2,kind=dp)) |
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| 52 | slat2=sin(real(rlat2,kind=dp)) |
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| 53 | cdlon=cos(real(rlon1-rlon2,kind=dp)) |
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| 54 | crd=slat1*slat2+clat1*clat2*cdlon |
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| 55 | distance2=real(rerth*acos(crd)/1000.0_dp) |
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| 56 | endif |
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| 57 | ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - |
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| 58 | end function distance2 |
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