# ARTS built-in documentation server

## Workspace Method ppathStepByStep

### Description

Standard method for calculation of propagation paths. This method calculates complete propagation paths in a stepwise manner. Each step is denoted as a "ppath_step" and is the path through/inside a single grid box. The definition of a propgation path cannot be accommodated here. For more information read the chapter on propagation paths in the ARTS user guide. This method should never be called directly. Use ppathCalc instead if you want to extract propagation paths.

**Authors: **Patrick Eriksson

### Synopsis

ppathStepByStep( | ppath, ppath_step_agenda, ppath_inside_cloudbox_do, atmosphere_dim, p_grid, lat_grid, lon_grid, z_field, f_grid, refellipsoid, z_surface, cloudbox_on, cloudbox_limits, rte_pos, rte_los, ppath_lmax, ppath_lraytrace ) |

### Variables

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

IN | ppath_step_agenda | (Agenda) | Calculation of a propagation path step. |

IN | ppath_inside_cloudbox_do | (Index) | Flag to perform ray tracing inside the cloudbox. |

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

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

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

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

IN | z_field | (Tensor3) | The field of geometrical altitudes. |

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

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

IN | z_surface | (Matrix) | The surface altitude. |

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

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

IN | rte_pos | (Vector) | A geographical position for starting radiative transfer calculations. |

IN | rte_los | (Vector) | A line-of-sight for (complete) radiative transfer calculations. |

IN | ppath_lmax | (Numeric) | Maximum length between points describing propagation paths. |

IN | ppath_lraytrace | (Numeric) | Maximum length of ray tracing steps when determining propagation paths. |