= PDAFomi_get_interp_coeff_tri =

This page documents the routine `PDAFomi_get_interp_coeff_tri` of PDAF-OMI.

The routine is called in `init_dim_obs_OBSTYPE of an obseration module to initialize interpolation coefficients for triangular interpolation
with barycentric coordinates. It is used if the observation operator performs linear interpolation (usually `PDAFomi_obs_op_interp_lin`).

|| See the [wiki:OMI_observation_operators page describing PDAF-OMI observation operators] for a general overview.||

The interface is:
{{{
  SUBROUTINE PDAFomi_get_interp_coeff_tri(gcoords, ocoords, icoeff)

    REAL, INTENT(in)    :: gcoords(:,:)  ! Coordinates of grid points; dim(3,2)
                                         !     3 rows; each containing lon and lat coordinates
    REAL, INTENT(in)    :: ocoords(:)    ! Coordinates of observation; dim(2)
    REAL, INTENT(inout) :: icoeff(:)     ! Interpolation coefficients; dim(3)
}}}

'''Note:'''
 * In the array `gcoords`, the first index specifies the grid point while the second specifies the coordinate, thus `gcoords(1,1)` is the first coordinate for grid point 1, `gcoords(1,2)` is the second coordiate for grid point 1, while `gcoords(2,1)` is the first coordiate for grid point 2. The coordinates need to be consistent with the indices specified in `thisobs%id_obs_p` since these specify the elements of the state vector that are interpolated. Only the first `n_dim` entries of ocoord will be used for the interpolation.