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subroutine da_llxy_rotated_latlon(lat,lon, proj, x, y) 1,2
!-----------------------------------------------------------------------
! Purpose: Compute the x/y location of a lat/lon on a rotated LATLON grid.
! Author : Syed RH Rizvi, MMM/NCAR
! 06/01/2008
!---------------------------------------------------------------------------
implicit none
real, intent(in) :: lat
real, intent(in) :: lon
type(proj_info), intent(in) :: proj
real, intent(out) :: x
real, intent(out) :: y
real :: rot_lat, rot_lon, deltalat,deltalon, lon360,latinc,loninc
real :: xlat, xlon, cen_lat, cen_lon
if (trace_use_frequent) call da_trace_entry
("da_llxy_rotated_latlon")
! To account for issues around the dateline, convert the incoming
! longitudes to be 0->360.0
if (lon < 0) then
lon360 = lon + 360.0
else
lon360 = lon
end if
xlat = deg_to_rad*lat
xlon = deg_to_rad*lon360
cen_lat = deg_to_rad*proj%lat1
cen_lon = deg_to_rad*proj%lon1
if (cen_lon < 0.) cen_lon = cen_lon + 360.
latinc = proj%latinc
loninc = proj%loninc
rot_lon = rad_to_deg*atan( cos(xlat) * sin(xlon-cen_lon)/ &
(cos(cen_lat)*cos(xlat)*cos(xlon-cen_lon) + sin(cen_lat)*sin(xlat)))
rot_lat = rad_to_deg*asin( cos(cen_lat)*sin(xlat) - sin(cen_lat)*cos(xlat)*cos(xlon-cen_lon))
deltalat = rot_lat
deltalon = rot_lon
! Compute x/y
x = proj%knowni + deltalon/loninc + 1.0
y = proj%knownj + deltalat/latinc + 1.0
if (trace_use_frequent) call da_trace_exit("da_llxy_rotated_latlon")
end subroutine da_llxy_rotated_latlon