improver.regrid.idw module

Inverse distance weighting interpolation functions

ecef_coords(lats, lons)

Transform latitude-longitude coordinates to earth centred, earth fixed cartesian XYZ coordinates.

Parameters:

• lats (ndarray) – Latitude coordinates.

• lons (ndarray) – Longitude coordinates.

Return type:

Tuple[ndarray, ndarray, ndarray]

Returns:

• X transformed coordinates.

• Y transformed coordinates.

• Z transformed coordinates.

inverse_distance_weighting(idw_out_indexes, in_latlons, out_latlons, indexes, weights, in_classified, out_classified)

Locating source points and calculating inverse distance weights for selective target points.

Parameters:

• idw_out_indexes (ndarray) – Selected target points which will use Inverse Distance Weighting(idw) approach.

• in_latlons (ndarray) – Source points’s latitude-longitudes.

• out_latlons (ndarray) – Target points’s latitude-longitudes.

• indexes (ndarray) – Array of source grid point number for all target grid points.

• weights (ndarray) – Array of source grid point weighting for all target grid points.

• in_classified (ndarray) – Land_sea type for source grid points (land ->True).

• out_classified (ndarray) – Land_sea type for target grid points (land ->True).

Return type:

Tuple[ndarray, ndarray, ndarray]

Returns:

• Updated Indexes - source grid point number for all target grid points.

• Updated weights - array from each target grid point to its source grid points.

• Output_points_no_match - special target points without matching source points.

nearest_input_pts(in_latlons, out_latlons, k)

Find k nearest source (input) points to each target (output) point, using a KDtree.

Parameters:

• in_latlons (ndarray) – Source grid points’ latitude-longitudes (N x 2).

• out_latlons (ndarray) – Target grid points’ latitude-longitudes (M x 2).

• k (int) – Number of points surrounding each output point.

Return type:

Tuple[ndarray, ndarray]

Returns:

• Distances from target grid point to source grid points (M x K).

• Indexes of those source points (M x K).