= PDAF_gather_obs_f2 = 

This page documents the routine `PDAF_gather_obs_f2` of PDAF, which was introduced with PDAF V1.13.

In the local filters (LESKTF, LETKF, LSEIK, LNETF) this routine gathers the process-local observation coordinates arrays and returns the cooridates for the full observation vector.

The routine depends on [wiki:PDAF_gather_dim_obs_f], which defines the process-local observation dimensions. Further, the related routine [wiki:PDAF_gather_obs_f] is used to collect the full state vector. 

The routine is typically used in the routines [wiki:init_dim_obs_f_pdaf] if the analysis step of the local filters is parallelized.

The interface is the following:
{{{
  SUBROUTINE PDAF_gather_obs_f2(coords_obs_p, coords_obs_f, nrows, status)
}}}
with the following arguments:
 * `coords_obs_p` : `real, intent(in), dimension(nrows, dim_obs_p)`[[BR]] Process-local observation coordinates array
 * `coords_obs_f` : `real, intent(out), dimension(nrows, dim_obs_f)`[[BR]] Full observation coordinates array
 * `nrows` : `integer, intent(in)`[[BR]] Number of rows in observation coordinates array
 * `status` : `integer, intent(out)`[[BR]] Status flag (0 for no error)

Notes:
 * The routine `PDAF_gather_dim_obs_f` has to be called once before using `PDAF_gather_obs_f` because it internally initializes the local observation dimensions for gathering. The most recent call to `PDAF_gather_dim_obs_f` defines the dimensions `dim_obs_p` and `dim_obs_f` used here.
 * The routine is used for a coordinate array which stores in each column the coordinates of one observation. Thus for a two-dimensional case, the size of `coords_obs_p` is `(2, dim_obs_p)` and `nrows=2` is used in the call to `PDAF_gather_obs_f2`.
 * If the coordindates are stored so that each row of `coords_obs_p` holds the coordinates of one observation the routine `PDAF_gather_obs_f` should be applied separate for each column to gather the full coordinates array. 
 * For cases with different observation types, the routine [wiki:PDAF_gather_obs_f2_flex] can be used. It does not rely on `PDAF_gather_dim_obs_f` and is hence easier to use. It was introduced in PDAF 1.14.