# ARTS built-in documentation server

## Workspace Method DOAngularGridsSet

### Description

Sets the angular grids for Discrete Ordinate type scattering
calculations.
This method sets the angular grids for the Discrete Ordinate type
scattering calculations (DOIT, DISORT). For down- und up-looking
geometries it suffices to define ``N_za_grid`` (both solvers) and
``N_aa_grid`` (DOIT). From these numbers equally spaced grids are
created and stored in the WSVs za_grid and aa_grid.
For limb simulations it is important to use an optimized zenith
angle grid with a very fine resolution around the horizon
(za=90 degrees). Such a grid can be generated using
doit_za_grid_optCalc. To be applied, the name of the file holding
the optimized angle grid has to be given (``za_grid_opt_file``).
When an optimized grid is present, the equidistant grid is used for
the calculation of the scattering integrals, while the optimized
grid is applied for the integration of the radiative transfer
equation. Otherwise the equidistant grid is used throughout. For
down-looking cases using the equidistant grid typically suffices
and speeds up the calculations.

**Authors: **Claudia Emde

### Synopsis

### Variables

OUT | doit_za_grid_size | (Index) | Number of equidistant grid points of the zenith angle grid. |

OUT | aa_grid | (Vector) | Azimuthal angle grid. |

OUT | za_grid | (Vector) | Zenith angle grid. |

GIN | N_za_grid | (Index) | Number of grid points in zenith angle grid. Recommended value is 19. |

GIN | N_aa_grid | (Index, Default: 1) | Number of grid points in azimuth angle grid. Recommended value is 37. |

GIN | za_grid_opt_file | (String, Default: "") | Name of special grid for RT part. |