True Winds (Foreign Grid)

This example demonstrates how to render "true" winds, when attached to data points given in a non-standard Coordinate Reference System (CRS).

📋 まとめ

The example constructs sample points on a North Polar Stereographic grid, and assigns synthetic vector values to them, representing wind data. These data are presented as "true" winds, i.e., eastward (U) and northward (V) vector components, therefore not related to the foreign sample points grid. This is a fairly typical real world use case.

A synthetic eastward wind with a constant 4.0 ms-1 is generated everywhere, so the final effect is clearly visible.

We use the geovista.bridge.Transform.from_points() method, passing the winds to the vectors keyword, and specifying the different CRS of both the sample points (crs) and the vectors (vectors_crs).

🏷 Tags: experimental 🧪 component: graticule component: texture component: vectors domain: meteorology filter: glyph version: 0.6.0

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Static Scene

Interactive Scene

from __future__ import annotations

import cartopy.crs as ccrs
import numpy as np
import pyvista as pv

import geovista as gv


def main() -> None:
    """Plot vectors on different CRS from points.

    Notes
    -----
    .. versionadded:: 0.6.0

    """
    # Create a stereographic CRS (foreign grid) for the sample points.
    crs_polar = ccrs.NorthPolarStereo()

    # Create a geographic (latitude/longitude) CRS for the vectors.
    crs_latlon = ccrs.Geodetic()

    # Create the polar grid points.
    x = np.linspace(-5.0e6, 5.0e6, 20)
    y = np.linspace(-4.0e6, 2.0e6, 20)
    xs, ys = np.meshgrid(x, y)

    # Create the eastward (us) and northward (vs) wind vector components.
    xs, ys = xs.flatten(), ys.flatten()
    us, vs = 4.0 * np.ones_like(xs), np.zeros_like(ys)

    # Create the point cloud mesh with attached wind vectors.
    mesh = gv.Transform.from_points(
        xs, ys, vectors=(us, vs), crs=crs_polar, vectors_crs=crs_latlon
    )

    # Generate a mesh containing arrow glyphs from the wind vectors.
    arrows = mesh.glyph(factor=0.02)

    # Now render the plotter scene.
    p = gv.GeoPlotter()
    p.add_mesh(arrows, color="red")
    p.add_base_layer(texture=gv.natural_earth_hypsometric())
    p.add_graticule()

    # Define a specific camera position and orientation.
    cpos = pv.CameraPosition(
        position=(0.60371, -0.01103, 3.06958),
        focal_point=(0.0, 0.0, 0.00289),
        viewup=(-0.98099, -0.01998, 0.19304),
    )

    p.add_axes()
    p.show(cpos=cpos)


if __name__ == "__main__":
    main()