da_lc_cone.inc

1 subroutine da_lc_cone(truelat1, truelat2, cone)
2 
3    !------------------------------------------------------------------------
4    ! Purpose: compute the cone factor of a Lambert Conformal projection
5    !------------------------------------------------------------------------
6 
7    implicit none
8     
9    real, intent(in)             :: truelat1  ! (-90 -> 90 degrees N)
10    real, intent(in)             :: truelat2  !   "   "  "   "     "
11    real, intent(out)            :: cone
12 
13    ! First, see if this is a secant or tangent projection.  For tangent
14    ! projections, truelat1 = truelat2 and the cone is tangent to the 
15    ! Earth's surface at this latitude.  For secant projections, the cone
16    ! intersects the Earth's surface at each of the distinctly different
17    ! latitudes
18    if (ABS(truelat1-truelat2) > 0.1) then
19       cone = ALOG10(COS(truelat1*rad_per_deg)) - &
20              ALOG10(COS(truelat2*rad_per_deg))
21       cone = cone /(ALOG10(TAN((45.0 - ABS(truelat1)/2.0) * rad_per_deg)) - &
22              ALOG10(TAN((45.0 - ABS(truelat2)/2.0) * rad_per_deg)))        
23    else
24       cone = Sin(ABS(truelat1)*rad_per_deg)  
25    end if
26 
27 end subroutine da_lc_cone
28 
29