# ARTS built-in documentation server

## Workspace Method surface_scalar_reflectivityFromGriddedField4

### Description

Extracts scalar surface reflectivities from a field of such data.
This method allows to specify a field of surface reflectivity for
automatic interpolation to points of interest. The position and
direction for which the reflectivity shall be extracted are given
by rtp_pos and rtp_los. The reflectivity field is expected to
be stored as:
GriddedField4:
Vector "Frequency" [N_f]
Vector "Incidence angle" [N_ia]
Vector "Latitude" [N_lat]
Vector "Longitude" [N_lon]
Tensor4 data[N_f][N_ia][N_lat][N_lon]
Grids for incidence angle, latitude and longitude must have a
length of >= 2 (ie. no automatic expansion). If the frequency grid
has length 1, this is taken as the reflectivity is constant,
following the definition of surface_scalar_reflectivity.
The interpolation is done in steps:
1: Linear interpolation for lat and lon (std. extrapolation).
2: Interpolation in incidence angle (std. extrapolation).
If the grid has a length of >= 4, cubic interpolation is
applied. Otherwise linear interpolation.
3. Linear interpolation if frequency (if input data have more
than one frequency).

**Authors: **Patrick Eriksson

### Synopsis

### Variables