# ARTS built-in documentation server

## Workspace Method TangentPointExtract

### Description

Finds the tangent point of a propagation path.
The tangent point is here defined as the point with the lowest
altitude (which differes from the definition used in the code
where it is the point with the lowest radius, or equally the point
with a zenith angle of 90 deg.)
The tangent point is returned as a vector, with columns matching
e.g. rte_pos. If the propagation path has no tangent point, the
vector is set to NaN.

**Authors: **Patrick Eriksson

### Synopsis

TangentPointExtract( | tan_pos, ppath ) |

### Variables

GOUT | tan_pos | (Vector) | The position vector of the tangent point. |

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