# ARTS built-in documentation server

## Workspace Method iyTransmissionStandard

### Description

Standard method for handling transmission measurements. Designed to be part of iy_main_agenda. Treatment of the cloudbox is incorporated (that is, no need to define iy_cloudbox_agenda). The transmitter is assumed to be placed at the end of provided ppath. The transmitted signal is taken from iy_transmitter. This signal is propagated along the path, considering attenuation alone. That is, the result of the method (iy) is the output of iy_transmitter multiplied with the transmittance along the propagation path. As mentioned, the given ppath determines the position of the transmitter. For clear-sky and no modification of ppath, this means that the transitter will either be found at the surface or at the top-of-the-atmosphere. If you want to maintain this even with an active cloudbox, calculate ppath as:: ppathCalc( cloudbox_on=0 ) Without setting cloudbox_on=0, the transmitter will end up inside or at the boundary of the cloudbox. Some auxiliary radiative transfer quantities can be obtained. Auxiliary quantities are selected by iy_aux_vars and returned by iy_aux. Valid choices for auxiliary data are: - ``"Radiative background"``: Index value flagging the radiative background. The following coding is used: 0=space, 1=surface and 2=cloudbox. The value is added to each column. - ``"Optical depth"``: Scalar optical depth between the observation point and the end of the present propagation path. Calculated based on the (1,1)-element of the transmittance matrix (1-based indexing), i.e. only fully valid for scalar RT. The value is added to each column. IMPORTANT: No jacobian calculation is supported when gas scattering is included! This will be implemented in a future version.

**Authors: **Patrick Eriksson, Richard Larsson

### Synopsis

### Variables

OUT | iy | (Matrix) | Monochromatic pencil beam radiance spectrum. |

OUT | iy_aux | (ArrayOfMatrix) | Data auxiliary to iy. |

OUT+IN | diy_dx | (ArrayOfTensor3) | Derivative of iy with respect to retrieval quantities. |

OUT | ppvar_p | (Vector) | Pressure along the propagation path. |

OUT | ppvar_t | (Vector) | Temperature along the propagation path. |

OUT | ppvar_nlte | (EnergyLevelMap) | Non-LTE temperatures/ratios along the propagation path. |

OUT | ppvar_vmr | (Matrix) | VMR values along the propagation path. |

OUT | ppvar_wind | (Matrix) | Winds along the propagation path. |

OUT | ppvar_mag | (Matrix) | Magnetic field along the propagation path. |

OUT | ppvar_pnd | (Matrix) | PND values along the propagation path. |

OUT | ppvar_f | (Matrix) | Doppler adjusted frequencies along the propagation path. |

OUT | ppvar_iy | (Tensor3) | iy-values along the propagation path. |

OUT | ppvar_trans_cumulat | (Tensor4) | The transmittance between the sensor and each point of the propagation path. |

OUT | ppvar_trans_partial | (Tensor4) | The transmittance between the points along the propagation path. |

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

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

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

IN | p_grid | (Vector) | The pressure grid. |

IN | t_field | (Tensor3) | The field of atmospheric temperatures. |

IN | nlte_field | (EnergyLevelMap) | The field of NLTE temperatures and/or ratios. |

IN | vmr_field | (Tensor4) | VMR field. |

IN | abs_species | (ArrayOfArrayOfSpeciesTag) | Tag groups for gas absorption. |

IN | wind_u_field | (Tensor3) | Zonal component of the wind field. |

IN | wind_v_field | (Tensor3) | Meridional component of the magnetic field. |

IN | wind_w_field | (Tensor3) | Vertical wind component field. |

IN | mag_u_field | (Tensor3) | Zonal component of the magnetic field. |

IN | mag_v_field | (Tensor3) | Meridional component of the magnetic field. |

IN | mag_w_field | (Tensor3) | Vertical component of the magnetic field. |

IN | cloudbox_on | (Index) | Flag to activate the cloud box. |

IN | cloudbox_limits | (ArrayOfIndex) | The limits of the cloud box. |

IN | gas_scattering_do | (Index) | Flag to activate gas scattering. |

IN | pnd_field | (Tensor4) | Particle number density field. |

IN | dpnd_field_dx | (ArrayOfTensor4) | Partial derivatives of pnd_field. |

IN | scat_species | (ArrayOfString) | Array of Strings defining the scattering species to consider. |

IN | scat_data | (ArrayOfArrayOfSingleScatteringData) | Array of single scattering data. |

IN | iy_aux_vars | (ArrayOfString) | Selection of quantities for iy_aux and when applicable also y_aux. |

IN | jacobian_do | (Index) | Flag to activate (clear-sky) Jacobian calculations. |

IN | jacobian_quantities | (ArrayOfRetrievalQuantity) | The retrieval quantities in the Jacobian matrix. |

IN | ppath | (Ppath) | The propagation path for one line-of-sight. |

IN | iy_transmitter | (Matrix) | Monochromatic pencil beam radiance spectrum of transmitter signal. |

IN | propmat_clearsky_agenda | (Agenda) | Calculate the absorption coefficient matrix. |

IN | water_p_eq_agenda | (Agenda) | Calculation of the saturation pressure of water. |

IN | gas_scattering_agenda | (Agenda) | Calculation of the gas scattering extinction and phase matrix. |

IN | iy_agenda_call1 | (Index) | Flag to handle recursive calls of iy_main_agenda The agenda iy_main_agenda can be used recursively and this flag is used to tell the methods inside the agenda which is the primary call. |

IN | iy_transmittance | (Tensor3) | Transmittance to be included in iy. |

IN | rte_alonglos_v | (Numeric) | Velocity along the line-of-sight to consider for a RT calculation. |