wradlib.vis.plot_ppi

wradlib.vis.plot_ppi(data, r=None, az=None, elev=0.0, site=None, proj=None, fig=None, ax=111, func='pcolormesh', rf=1.0, **kwargs)

Plots a Plan Position Indicator (PPI).

This is a small wrapper around xarray dataarray. The radar data, coordinates and metadata is transformed into an xarray dataarray. Using the wradlib dataarray accessor the dataarray is enabled to plot polar data.

Using proj=cg the plotting is done in a curvelinear grid axes. Additional data can be plotted in polar coordinates or cartesian coordinates depending which axes object is used.

**kwargs may be used to try to influence the matplotlib.pyplot.pcolormesh, matplotlib.pyplot.contour, matplotlib.pyplot.contourf and wradlib.georef.polar.spherical_to_proj routines under the hood.

Concerning the values of r, az, elev, r should give the location of the center of each range bin, az and elev should give the angle at the center of the beam.

Parameters:
  • data (numpy.ndarray) – The data to be plotted. It is assumed that the first dimension is over the azimuth angles, while the second dimension is over the range bins
  • r (numpy.ndarray) – The ranges. Units may be chosen arbitrarily, unless proj is set. In that case the units must be meters. If None, a default is calculated from the dimensions of data.
  • rf (float) – If present, factor for scaling range axes, defaults to 1.
  • az (numpy.ndarray) – The azimuth angles in degrees. If None, a default is calculated from the dimensions of data.
  • elev (float or array of same shape as az) – Elevation angle of the scan or individual azimuths. May improve georeferencing coordinates for larger elevation angles.
  • site (tuple or None) – Tuple of coordinates of the radar site. If proj is not used, this simply becomes the offset for the origin of the coordinate system. If proj is used, values must be given as (longitude, latitude, altitude) tuple of geographical coordinates. Defaults to None.
  • proj (GDAL OSR SRS | cartopy CRS | curvelinear grid dict | None) – GDAL OSR Spatial Reference Object describing projection If this parameter is not None, site must be set. Then the function will attempt to georeference the radar bins and display the PPI in the coordinate system defined by the projection string.
  • fig (matplotlib.figure.Figure) – If given, the PPI will be plotted into this figure object. Axes are created as needed. If None, a new figure object will be created or current figure will be used, depending on ax.
  • ax (matplotlib.axes.Axes | matplotlib grid definition) – If matplotlib Axes object is given, the PPI will be plotted into this axes object. If matplotlib grid definition is given (nrows/ncols/plotnumber), axis are created in the specified place. Defaults to ‘111’, only one subplot/axis.
  • func (str) – Name of plotting function to be used under the hood. Defaults to ‘pcolormesh’. ‘contour’ and ‘contourf’ can be selected too.
Returns:

Note

If proj=``cg``, the cgax - curvelinear Axes (r-theta-grid) is returned. caax - Cartesian Axes (x-y-grid) and paax - parasite axes object for plotting polar data can be derived like this:

caax = cgax.parasites[0]
paax = cgax.parasites[1]

The function create_cg uses the Matplotlib AXISARTIST namespace mpl_toolkits.axisartist.

Here are some limitations to normal Matplotlib Axes. See AxesGridToolkitUserGuide.

Examples

See Quick-view a sweep in polar or cartesian reference systems, and Plot data to curvelinear grid.