# ARTS built-in documentation server

## Workspace Method ppathPlaneParallel

### Description

Propagation path calculations for a plane parallel atmosphere. This method basically assumes that the planet's radius is infinite, i.e. the planet surface has no curvature. Some consequences of this assumption: - the mathod can only be used for 1D - zenith angles between 89.9 and 90.1 deg are not allowed - refraction is always neglected - radii in ppath are set to Inf Notice that the method provides full propagation paths. This means that ppath_step_agenda is ignored (and thus also refraction). On the other hand, the method considers the cloudbox exactly as the standard path calculations.

**Authors: **Patrick Eriksson

### Synopsis

ppathPlaneParallel( | ppath, atmosphere_dim, z_field, z_surface, cloudbox_on, cloudbox_limits, ppath_inside_cloudbox_do, rte_pos, rte_los, ppath_lmax ) |

### Variables

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

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

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

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

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. |