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130 lines
3.1 KiB
Fortran
130 lines
3.1 KiB
Fortran
subroutine azdist(grid1,grid2,utch,nAz,nEl,nDmiles,nDkm,nHotAz,nHotABetter)
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character*(*) grid1,grid2
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character*6 MyGrid,HisGrid,mygrid0,hisgrid0
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real*8 utch,utch0
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logical HotABetter,IamEast
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real eltab(22),daztab(22)
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data eltab/18.,15.,13.,11.,9.,8.,7.,6.,5.3,4.7,4.,3.3,2.7, &
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2.,1.5,1.,0.8,0.6,0.4,0.2,0.0,0.0/
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data daztab/21.,18.,16.,15.,14.,13.,12.,11.,10.7,10.3,10., &
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10.,10.,10.,10.,10.,10.,9.,9.,9.,8.,8./
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data mygrid0/" "/,hisgrid0/" "/,utch0/-999.d0/
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save
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MyGrid=grid1//' '
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HisGrid=grid2//' '
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if(ichar(MyGrid(5:5)).eq.0) MyGrid(5:6)=' '
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if(ichar(HisGrid(5:5)).eq.0) HisGrid(5:6)=' '
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if(MyGrid.eq.HisGrid) then
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naz=0
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nel=0
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ndmiles=0
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ndkm=0
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nhotaz=0
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nhotabetter=1
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go to 999
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endif
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if(mygrid.eq.mygrid0 .and. hisgrid.eq.hisgrid0 .and. &
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abs(utch-utch0).lt.0.1666667d0) go to 900
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utch0=utch
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mygrid0=mygrid
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hisgrid0=hisgrid
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utchours=utch
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if(MyGrid(5:5).eq.' ') MyGrid(5:5)='m'
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if(MyGrid(6:6).eq.' ') MyGrid(6:6)='m'
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if(HisGrid(5:5).eq.' ') HisGrid(5:5)='m'
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if(HisGrid(6:6).eq.' ') HisGrid(6:6)='m'
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if(MyGrid.eq.HisGrid) then
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Az=0.
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Dmiles=0.
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Dkm=0.0
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El=0.
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HotA=0.
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HotB=0.
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HotABetter=.true.
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go to 900
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endif
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call grid2deg(MyGrid,dlong1,dlat1)
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call grid2deg(HisGrid,dlong2,dlat2)
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eps=1.e-6
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Az=0.
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Dmiles=0.
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Dkm=0.0
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El=0.
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HotA=0.
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HotB=0.
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HotABetter=.true.
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if(abs(dlat1-dlat2).lt.eps .and. abs(dlong1-dlong2).lt.eps) go to 900
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difflong=mod(dlong1-dlong2+720.0,360.0)
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if(abs(dlat1+dlat2).lt.eps .and. abs(difflong-180.0).lt.eps) then
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! Antipodes
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Dkm=20400
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go to 900
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endif
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call geodist(dlat1,dlong1,dlat2,dlong2,Az,Baz,Dkm)
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ndkm=Dkm/100
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j=ndkm-4
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if(j.lt.1) j=1
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if(j.gt.21)j=21
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if(Dkm.lt.500.0) then
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El=18.0
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else
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u=(Dkm-100.0*ndkm)/100.0
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El=(1.0-u)*eltab(j) + u*eltab(j+1)
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endif
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daz=daztab(j) + u * (daztab(j+1)-daztab(j))
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Dmiles=Dkm/1.609344
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tmid=mod(UTChours-0.5*(dlong1+dlong2)/15.0+48.0,24.0)
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IamEast=.false.
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if(dlong1.lt.dlong2) IamEast=.true.
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if(dlong1.eq.dlong2 .and. dlat1.gt.dlat2) IamEast=.false.
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azEast=baz
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if(IamEast) azEast=az
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if((azEast.ge.45.0 .and. azEast.lt.135.0) .or. &
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(azEast.ge.225.0 .and. azEast.lt.315.0)) then
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! The path will be taken as "east-west".
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HotABetter=.true.
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if(abs(tmid-6.0).lt.6.0) HotABetter=.false.
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if((dlat1+dlat2)/2.0 .lt. 0.0) HotABetter=.not.HotABetter
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else
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! The path will be taken as "north-south".
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HotABetter=.false.
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if(abs(tmid-12.0).lt.6.0) HotABetter=.true.
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endif
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if(IamEast) then
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HotA = Az - daz
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HotB = Az + daz
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else
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HotA = Az + daz
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HotB = Az - daz
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endif
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if(HotA.lt.0.0) HotA=HotA+360.0
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if(HotA.gt.360.0) HotA=HotA-360.0
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if(HotB.lt.0.0) HotB=HotB+360.0
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if(HotB.gt.360.0) HotB=HotB-360.0
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900 continue
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naz=nint(Az)
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nel=nint(el)
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nDmiles=nint(Dmiles)
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nDkm=nint(Dkm)
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nHotAz=nint(HotB)
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nHotABetter=0
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if(HotABetter) then
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nHotAz=nint(HotA)
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nHotABetter=1
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endif
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999 return
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end subroutine azdist
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