# ARTS built-in documentation server

## Workspace Method ppathFixedLstep

### Description

Full propagation path calculation with fixed step length.
Restrictions:
1. An active cloudbox is not handled (causes an error).
2. Observations of limb sounding type not handled. That is, zenith
angles between 90 and about 120 deg will cause an error.
3. Unsuitable for downward observation from within the atmosphere.
The method determines the lowest point of the propagation path and
applies a fixed step length from that point. This point can be the
surface intersection or the sensor position depending on observation
geometry.
There is no adjustment at the high altitude end, neither to the top
of the atmosphere altitude nor the sensor's altitude.
Default is to apply a step length of ppath_lmax everywhere.
By setting *za_scale* to 1, the step length is scaled with zenith
angle and the steps are rather constant in altitude spacing.
With *z_coarse* and *l_coarse* you can introduce another step length
at higher altitudes. If *z_coarse* is > 0, then *l_coarse* is applied
above *z_coarse*, instead of ppath_lmax. *za_scale* is considered
also for *l_coarse*.

**Authors: **Patrick Eriksson

### Synopsis

ppathFixedLstep( | ppath, atmfields_checked, atmgeom_checked, atmosphere_dim, lat_grid, lon_grid, z_field, refellipsoid, z_surface, cloudbox_on, rte_pos, rte_los, ppath_lmax, za_scale, z_coarse, l_coarse ) |

### Variables