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subroutine da_llxy_lc(lat, lon, proj, x, y) 2,2
!-----------------------------------------------------------------------
! Purpose: compute the geographical latitude and longitude values
! to the cartesian x/y on a Lambert Conformal projection.
!-----------------------------------------------------------------------
implicit none
real, intent(in) :: lat ! Latitude (-90->90 deg N)
real, intent(in) :: lon ! Longitude (-180->180 E)
type(proj_info),intent(in) :: proj ! Projection info structure
real, intent(out) :: x ! Cartesian X coordinate
real, intent(out) :: y ! Cartesian Y coordinate
real :: arg
real :: deltalon
real :: tl1r
real :: rm
real :: ctl1r
if (trace_use_dull) call da_trace_entry
("da_llxy_lc")
! Compute deltalon between known longitude and standard lon and ensure
! it is not in the cut zone
deltalon = lon - proj%stdlon
if (deltalon > +180.0) deltalon = deltalon - 360.0
if (deltalon < -180.0) deltalon = deltalon + 360.0
! Convert truelat1 to radian and compute COS for later use
tl1r = proj%truelat1 * rad_per_deg
ctl1r = COS(tl1r)
! Radius to desired point
rm = proj%rebydx * ctl1r/proj%cone * &
(TAN((90.0*proj%hemi-lat)*rad_per_deg/2.0) / &
TAN((90.0*proj%hemi-proj%truelat1)*rad_per_deg/2.0))**proj%cone
arg = proj%cone*(deltalon*rad_per_deg)
x = proj%polei + proj%hemi * rm * Sin(arg)
y = proj%polej - rm * COS(arg)
! Finally, if we are in the southern hemisphere, flip the i/j
! values to a coordinate system where (1,1) is the SW corner
! (what we assume) which is different than the original NCEP
! algorithms which used the NE corner as the origin in the
! southern hemisphere (left-hand vs. right-hand coordinate?)
if (proj%hemi == -1.0) then
x = 2.0 - x
y = 2.0 - y
end if
if (trace_use_dull) call da_trace_exit("da_llxy_lc")
end subroutine da_llxy_lc