EFORM Subroutine

  1. astro_module.f90
  2. astro_module
  3. EFORM

public subroutine EFORM(n, a, f, j)

Earth reference ellipsoids.

Status: canonical.

Notes

  1. The identifier N is a number that specifies the choice of reference ellipsoid. The following are supported:

    N   ellipsoid

1    WGS84
2    GRS80
3    WGS72

    The number N has no significance outside the SOFA software.

  2. The ellipsoid parameters are returned in the form of equatorial radius in meters (A) and flattening (F). The latter is a number around 0.00335, i.e. around 1/298.

  3. For the case where an unsupported N value is supplied, zero A and F are returned, as well as error status.

References

  • Department of Defense World Geodetic System 1984, National Imagery and Mapping Agency Technical Report 8350.2, Third Edition, p3-2.

  • Moritz, H., Bull. Geodesique 66-2, 187 (1992).

  • The Department of Defense World Geodetic System 1972, World Geodetic System Committee, May 1974.

  • Explanatory Supplement to the Astronomical Almanac, P. Kenneth Seidelmann (ed), University Science Books (1992), p220.

History

  • IAU SOFA revision: 2010 January 18

Arguments

TypeIntentOptionalAttributesName
integer, intent(in) :: n

ellipsoid identifier (Note 1)
real(kind=wp), intent(out) :: a

equatorial radius (meters, Note 2)
real(kind=wp), intent(out) :: f

flattening (Note 2)
integer, intent(out) :: j
  • 0 = OK
  • -1 = illegal identifier (Note 3)

Called by

proc~~eform~~CalledByGraph proc~eform EFORM proc~gd2gc GD2GC proc~gd2gc->proc~eform proc~gc2gd GC2GD proc~gc2gd->proc~eform proc~pvtob PVTOB proc~pvtob->proc~gd2gc proc~apco APCO proc~apco->proc~pvtob proc~apio APIO proc~apio->proc~pvtob proc~apco13 APCO13 proc~apco13->proc~apco proc~apio13 APIO13 proc~apio13->proc~apio proc~atco13 ATCO13 proc~atco13->proc~apco13 proc~atoi13 ATOI13 proc~atoi13->proc~apio13 proc~atio13 ATIO13 proc~atio13->proc~apio13 proc~atoc13 ATOC13 proc~atoc13->proc~apco13

Contents

Source Code

EFORM

Source Code

    subroutine EFORM ( n, a, f, j )

    implicit none

    integer,intent(in) :: n !! ellipsoid identifier (Note 1)
    real(wp),intent(out) :: a !! equatorial radius (meters, Note 2)
    real(wp),intent(out) :: f !! flattening (Note 2)
    integer,intent(out) :: j !! status:
                             !! * 0 = OK
                             !! * -1 = illegal identifier (Note 3)

    !  Preset the status to OK
    j = 0

    !  Look up A and F for the specified reference ellipsoid.

    select case (n)
    case ( 1 )

       !  WGS84.
       a = 6378137.0_wp
       f = 1.0_wp / 298.257223563_wp

    case ( 2 )

       !  GRS80.
       a = 6378137.0_wp
       f = 1.0_wp / 298.257222101_wp

    case ( 3 )

       !  WGS72.
       a = 6378135.0_wp
       f = 1.0_wp / 298.26_wp

    case default

       !  Invalid identifier.
       a = 0.0_wp
       f = 0.0_wp
       j = -1

    end select

    end subroutine EFORM