"""
Working with spatio-temporal lat-lon fields
-------------------------------------------

In this example, we demonstrate how to generate a spatio-temporal
random field on geographical coordinates.

First we setup a model, with ``latlon=True`` and ``temporal=True``,
to get the associated spatio-temporal Yadrenko model.

In addition, we will use a kilometer scale provided by :any:`KM_SCALE`
as ``geo_scale`` to have a meaningful length scale in km.
By default the length scale would be given in radians (:any:`RADIAN_SCALE`).
A third option is a length scale in degrees (:any:`DEGREE_SCALE`).

To generate the field, we simply pass ``(lat, lon, time)`` as the position tuple
to the :any:`SRF` class.

We will set a spatial length-scale of `1000` and a time length-scale of `100` days.
"""

import numpy as np

import gstools as gs

model = gs.Matern(
    latlon=True,
    temporal=True,
    var=1,
    len_scale=[1000, 100],
    geo_scale=gs.KM_SCALE,
)

lat = lon = np.linspace(-80, 81, 50)
time = np.linspace(0, 777, 50)
srf = gs.SRF(model, seed=1234)
field = srf.structured((lat, lon, time))
srf.plot()