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transverse mercator (tmerc) projection bug fix #223

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transverse mercator (tmerc) projection bug fix #223

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1dc799c
adding truelat1 parameter to mercator coordinate transformation funct…
ramespada Oct 19, 2023
ed4f99f
Merge branch 'USEPA:main' into proj_tmerc
ramespada Dec 5, 2024
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11 changes: 7 additions & 4 deletions PREP/mcip/src/ll2xy_merc.f90
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,7 @@
! subject to their copyright restrictions. !
!------------------------------------------------------------------------------!

SUBROUTINE ll2xy_merc (phi, lambda, lambda0, xx, yy)
SUBROUTINE ll2xy_merc (phi, lambda, truelat1, lambda0, xx, yy)

!-------------------------------------------------------------------------------
! Name: Latitude-Longitude to (X,Y) for Mercator Projection
Expand Down Expand Up @@ -45,7 +45,9 @@ SUBROUTINE ll2xy_merc (phi, lambda, lambda0, xx, yy)
REAL(8) :: piover4 ! pi/4
REAL, INTENT(OUT) :: xx ! X-coordinate from origin
REAL, INTENT(OUT) :: yy ! Y-coordinate from origin

REAL(8) :: k0
REAL, INTENT(IN) :: truelat1
REAL(8) :: truelat1rad
!-------------------------------------------------------------------------------
! Compute constants.
!-------------------------------------------------------------------------------
Expand All @@ -64,7 +66,8 @@ SUBROUTINE ll2xy_merc (phi, lambda, lambda0, xx, yy)
lambdarad = DBLE(lambda) * deg2rad ! convert degrees to radians
lambda0rad = DBLE(lambda0) * deg2rad ! convert degrees to radians

xx = REAL( drearth * (lambdarad - lambda0rad) )
yy = REAL( drearth * DLOG( DTAN( piover4 + (phirad/2.0d0) ) ) )
k0=DCOS(DBLE(truelat1rad))

xx = REAL( k0 * drearth * (lambdarad - lambda0rad) )
yy = REAL( k0 * drearth * DLOG( DTAN( piover4 + (phirad/2.0d0) ) ) )
END SUBROUTINE ll2xy_merc
6 changes: 3 additions & 3 deletions PREP/mcip/src/rdwrfem.f90
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Expand Up @@ -2180,7 +2180,7 @@ SUBROUTINE rdwrfem (mcip_now)
yyin = met_yyctr - &
( met_rjctr_dot - (FLOAT(j) + yoff) ) * met_resoln

CALL xy2ll_merc (xxin, yyin, met_proj_clon, &
CALL xy2ll_merc (xxin, yyin, met_tru1, met_proj_clon, &
latdot(i,j), londot(i,j))

mapdot(i,j) = mapfac_merc (latdot(i,j))
Expand All @@ -2202,7 +2202,7 @@ SUBROUTINE rdwrfem (mcip_now)
yyin = met_yyctr - &
( met_rjctr_dot - (FLOAT(j) + yoff) ) * met_resoln

CALL xy2ll_merc (xxin, yyin, met_proj_clon, &
CALL xy2ll_merc (xxin, yyin, met_tru1, met_proj_clon, &
latu(i,j), lonu(i,j))

mapu(i,j) = mapfac_merc (latu(i,j))
Expand All @@ -2222,7 +2222,7 @@ SUBROUTINE rdwrfem (mcip_now)
yyin = met_yyctr - &
( met_rjctr_dot - (FLOAT(j) + yoff) ) * met_resoln

CALL xy2ll_merc (xxin, yyin, met_proj_clon, &
CALL xy2ll_merc (xxin, yyin, met_tru1, met_proj_clon, &
latv(i,j), lonv(i,j))

mapv(i,j) = mapfac_merc (latv(i,j))
Expand Down
4 changes: 2 additions & 2 deletions PREP/mcip/src/setup_wrfem.f90
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Expand Up @@ -488,13 +488,13 @@ SUBROUTINE setup_wrfem (cdfid, ctmlays)
met_xxctr, met_yyctr)

CASE (3) ! Mercator
met_p_alp_d = 0.0 ! lat of coord origin [deg]
met_p_alp_d = met_tru1 ! lat of coord origin [deg]
met_p_bet_d = 0.0 ! (not used)
met_p_gam_d = met_proj_clon ! lon of coord origin [deg]
met_cone_fac = 0.0 ! cone factor
met_ref_lat = -999.0 ! not used

CALL ll2xy_merc (met_cen_lat, met_cen_lon, met_proj_clon, &
CALL ll2xy_merc (met_cen_lat, met_cen_lon, met_tru1, met_proj_clon, &
met_xxctr, met_yyctr)

CASE DEFAULT
Expand Down
12 changes: 6 additions & 6 deletions PREP/mcip/src/xy2ll_merc.f90
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,7 @@
! subject to their copyright restrictions. !
!------------------------------------------------------------------------------!

SUBROUTINE xy2ll_merc (xx, yy, lambda0, phi, lambda)
SUBROUTINE xy2ll_merc (xx, yy, truelat1, lambda0, phi, lambda)

!-------------------------------------------------------------------------------
! Name: (X,Y) to Latitude-Longitude for Polar Stereographic Projection
Expand Down Expand Up @@ -48,7 +48,8 @@ SUBROUTINE xy2ll_merc (xx, yy, lambda0, phi, lambda)
REAL(8) :: xxd
REAL, INTENT(IN) :: yy ! Y-coordinate from origin
REAL(8) :: yyd

REAL(8) :: k0
REAL, INTENT(IN) :: truelat1
!-------------------------------------------------------------------------------
! Compute constants.
!-------------------------------------------------------------------------------
Expand All @@ -60,7 +61,7 @@ SUBROUTINE xy2ll_merc (xx, yy, lambda0, phi, lambda)
rad2deg = 1.8d2 / pi

drearth = DBLE(rearth)

k0=DCOS(DBLE(truelat1*deg2rad))
!-------------------------------------------------------------------------------
! Set up geometric constants.
!-------------------------------------------------------------------------------
Expand All @@ -71,16 +72,15 @@ SUBROUTINE xy2ll_merc (xx, yy, lambda0, phi, lambda)
!-------------------------------------------------------------------------------
! Compute latitude (PHI).
!-------------------------------------------------------------------------------

phirad = ( 2.0d0 * DATAN ( DEXP(yyd/drearth) ) ) - piover2
phirad = piover2 - 2.0d0 * DATAN ( DEXP(- yyd/drearth/k0) )
phi = REAL( phirad * rad2deg )

!-------------------------------------------------------------------------------
! Compute longitude (LAMBDA).
!-------------------------------------------------------------------------------

lambda0rad = DBLE(lambda0) * deg2rad
lambdarad = lambda0rad + xxd/drearth
lambdarad = lambda0rad + xxd/drearth/k0
lambda = REAL( lambdarad * rad2deg )

END SUBROUTINE xy2ll_merc