[6] | 1 | !********************************************************************** |
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| 2 | ! Copyright 1998,1999,2000,2001,2002,2005,2007,2008,2009,2010 * |
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| 3 | ! Andreas Stohl, Petra Seibert, A. Frank, Gerhard Wotawa, * |
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| 4 | ! Caroline Forster, Sabine Eckhardt, John Burkhart, Harald Sodemann * |
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| 5 | ! * |
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| 6 | ! This file is part of FLEXPART. * |
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| 7 | ! * |
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| 8 | ! FLEXPART is free software: you can redistribute it and/or modify * |
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| 9 | ! it under the terms of the GNU General Public License as published by* |
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| 10 | ! the Free Software Foundation, either version 3 of the License, or * |
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| 11 | ! (at your option) any later version. * |
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| 12 | ! * |
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| 13 | ! FLEXPART is distributed in the hope that it will be useful, * |
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| 14 | ! but WITHOUT ANY WARRANTY; without even the implied warranty of * |
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| 15 | ! MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * |
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| 16 | ! GNU General Public License for more details. * |
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| 17 | ! * |
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| 18 | ! You should have received a copy of the GNU General Public License * |
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| 19 | ! along with FLEXPART. If not, see <http://www.gnu.org/licenses/>. * |
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| 20 | !********************************************************************** |
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| 21 | |
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| 22 | subroutine centerofmass(xl,yl,n,xcenter,ycenter) |
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| 23 | ! i i i o o |
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| 24 | !***************************************************************************** |
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| 25 | ! * |
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| 26 | ! This routine calculates the center of mass of n points on the Earth. * |
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| 27 | ! Input are the longitudes (xl) and latitudes (yl) of the individual * |
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| 28 | ! points, output is the longitude and latitude of the centre of mass. * |
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| 29 | ! * |
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| 30 | ! Author: A. Stohl * |
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| 31 | ! * |
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| 32 | ! 24 January 2002 * |
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| 33 | ! * |
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| 34 | !***************************************************************************** |
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| 35 | |
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| 36 | use par_mod |
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| 37 | |
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| 38 | implicit none |
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| 39 | |
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| 40 | integer :: n,l |
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| 41 | real :: xl(n),yl(n),xll,yll,xav,yav,zav,x,y,z,xcenter,ycenter |
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| 42 | |
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| 43 | |
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| 44 | xav=0. |
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| 45 | yav=0. |
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| 46 | zav=0. |
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| 47 | |
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| 48 | do l=1,n |
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| 49 | |
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| 50 | ! Convert longitude and latitude from degrees to radians |
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| 51 | !******************************************************* |
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| 52 | |
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| 53 | xll=xl(l)*pi180 |
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| 54 | yll=yl(l)*pi180 |
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| 55 | |
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| 56 | ! Calculate 3D coordinates from longitude and latitude |
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| 57 | !***************************************************** |
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| 58 | |
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| 59 | x = cos(yll)*sin(xll) |
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| 60 | y = -1.*cos(yll)*cos(xll) |
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| 61 | z = sin(yll) |
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| 62 | |
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| 63 | |
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| 64 | ! Find the mean location in Cartesian coordinates |
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| 65 | !************************************************ |
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| 66 | |
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| 67 | xav=xav+x |
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| 68 | yav=yav+y |
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| 69 | zav=zav+z |
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| 70 | end do |
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| 71 | |
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| 72 | xav=xav/real(n) |
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| 73 | yav=yav/real(n) |
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| 74 | zav=zav/real(n) |
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| 75 | |
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| 76 | |
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| 77 | ! Project the point back onto Earth's surface |
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| 78 | !******************************************** |
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| 79 | |
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| 80 | xcenter=atan2(xav,-1.*yav) |
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| 81 | ycenter=atan2(zav,sqrt(xav*xav+yav*yav)) |
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| 82 | |
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| 83 | ! Convert back to degrees |
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| 84 | !************************ |
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| 85 | |
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| 86 | xcenter=xcenter/pi180 |
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| 87 | ycenter=ycenter/pi180 |
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| 88 | |
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| 89 | end subroutine centerofmass |
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