#!/usr/bin/env python3
"""
Plotting utilities
Cartographic and visualization functions for oceanographic data.
"""
import cartopy.crs as ccrs
import matplotlib.pyplot as plt
import numpy as np
from . import geo as sgeo
pmerc = ccrs.Mercator()
pcarr = ccrs.PlateCarree()
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def plot_ellipse(lon, lat, a, b, angle, ax=None, npts=100, **kwargs):
"""Plot geographic ellipse
Parameters
----------
lon : float
Center longitude in degrees.
lat : float
Center latitude in degrees.
a : float
Semi-major axis in kilometers.
b : float
Semi-minor axis in kilometers.
angle : float
Orientation angle in degrees.
ax : matplotlib.axes.Axes, optional
Axes to plot on. Uses current axes if None.
npts : int, default 100
Number of points for ellipse outline.
**kwargs
Additional plot styling arguments.
Returns
-------
list
Matplotlib line objects.
"""
if ax is None:
ax = plt.gca()
theta = np.radians(angle)
ca = np.cos(theta)
sa = np.sin(theta)
angles = np.linspace(0, 360.0, npts)
alphas = np.radians(angles)
cas = np.cos(alphas)
sas = np.sin(alphas)
am = a * 1e3
bm = b * 1e3
lons = lon + sgeo.m2deg(am * ca * cas - bm * sa * sas, lat)
lats = lat + sgeo.m2deg(am * sa * cas + bm * ca * sas)
pe = ax.plot(lons, lats, **kwargs)
return pe
[docs]
def create_map(
lons,
lats,
margin=0.0,
square=False,
coastlines=True,
emodnet=False,
projection=pmerc,
title=None,
**kwargs,
):
"""Create cartographic map for oceanographic data
Parameters
----------
lons : array-like
Longitude coordinates in degrees.
lats : array-like
Latitude coordinates in degrees.
margin : float, default 0.0
Fractional margin around data extent.
square : bool, default False
Force square aspect ratio.
coastlines : bool, default True
Draw coastlines.
emodnet : bool, default False
Use EMODnet bathymetry background.
projection : cartopy.crs.Projection, default Mercator
Map projection.
title : str, optional
Map title.
**kwargs
Additional arguments for plt.subplots.
Returns
-------
fig : matplotlib.figure.Figure
Figure object.
ax : matplotlib.axes.Axes
Cartographic axes.
"""
xmin, xmax = np.min(lons), np.max(lons)
ymin, ymax = np.min(lats), np.max(lats)
dx, dy = xmax - xmin, ymax - ymin
x0, y0 = 0.5 * (xmin + xmax), 0.5 * (ymin + ymax)
if square:
aspect = dx / dy * np.cos(np.radians(y0))
if aspect > 1:
dy *= aspect
else:
dx /= aspect
xmargin = margin * dx
ymargin = margin * dy
xmin = x0 - 0.5 * dx - xmargin
xmax = x0 + 0.5 * dx + xmargin
ymin = y0 - 0.5 * dy - ymargin
ymax = y0 + 0.5 * dy + ymargin
fig, ax = plt.subplots(1, subplot_kw=dict(projection=projection), **kwargs)
ax.set_extent([xmin, xmax, ymin, ymax])
ax.gridlines(
draw_labels=["bottom", "left"],
linewidth=1,
color='k',
alpha=0.5,
linestyle='--',
rotate_labels=False,
)
if coastlines:
ax.coastlines()
if emodnet:
ax.add_wms("https://ows.emodnet-bathymetry.eu/wms", "emodnet:mean_atlas_land")
if title:
ax.set_title(title)
return fig, ax
