# ARTS built-in documentation server

## Workspace Method surface_rtpropFromTypesAverage

### Description

Extracts surface RT properties by averaging. This method allows to let one pencil beam calculation represent an area when it comes to surface RT properties. The surface is sampled at a set of positions. The sampling is defined as a set of angles by the WSV dlos. A weight must be specified for each angle by dlos_weight_vector. These weights should represent the solid angle each dlos covers, but can also include other weighting factors such as antenna pattern. The sum of dlos_weight_vector is internally normalised to 1. All the output variables are a weighted average between the surface types inside the area sampled.

**Authors: **Patrick Eriksson

### Synopsis

surface_rtpropFromTypesAverage( | surface_type_mix, surface_skin_t, surface_los, surface_rmatrix, surface_emission, f_grid, stokes_dim, atmosphere_dim, lat_grid, lon_grid, lat_true, lon_true, rtp_pos, rtp_los, refellipsoid, surface_type_mask, surface_rtprop_agenda_array, z_sensor, dlos, dlos_weight_vector ) |

### Variables

OUT | surface_type_mix | (Vector) | Gives the fraction of different surface types. |

OUT | surface_skin_t | (Numeric) | Surface skin temperature. |

OUT | surface_los | (Matrix) | Downwelling radiation directions to consider in surface reflection. |

OUT | surface_rmatrix | (Tensor4) | The reflection coefficients for the directions given by surface_los to the direction of interest. |

OUT | surface_emission | (Matrix) | The emission from the surface. |

IN | f_grid | (Vector) | The frequency grid for monochromatic pencil beam calculations. |

IN | stokes_dim | (Index) | The dimensionality of the Stokes vector (1-4). |

IN | atmosphere_dim | (Index) | The atmospheric dimensionality (1-3). |

IN | lat_grid | (Vector) | The latitude grid. |

IN | lon_grid | (Vector) | The longitude grid. |

IN | lat_true | (Vector) | Latitudinal geolocation for 1D and 2D data. |

IN | lon_true | (Vector) | Longitudinal geolocation for 1D and 2D data. |

IN | rtp_pos | (Vector) | Position of a radiative transfer point. |

IN | rtp_los | (Vector) | Line-of-sight at a radiative transfer point. |

IN | refellipsoid | (Vector) | Reference ellipsoid. |

IN | surface_type_mask | (GriddedField2) | Classification of the surface using a type coding. |

IN | surface_rtprop_agenda_array | (ArrayOfAgenda) | Description of surface radiative properties, for each surface type. |

IN | z_sensor | (Numeric) | The altitude of the sensor. |

IN | dlos | (Matrix) | A set of relative angles. |

IN | dlos_weight_vector | (Vector) | A weight associated with each direction dlos. |