Interpolation

This page lists the methods that provide interpolation of the terrain data.

Alphabetical list:

• linear_interpolant

• spline()

class nevis.linear_interpolant(grad=False)

Returns a linear interpolation and optionally its gradient over the full GB data set.

When grad is set to False (by default), the returned function takes two arguments x and y (both in metres) and returns an interpolated height z (in meters).

When grad is set to True, the returned function takes two arguments x and y (both in metres) and returns a tuple (z, g), where z is an interpolated height (in meters) and g is a tuple (dz/dx, dz/dy).

The height for each grid point (i, j) is assumed to be in the center of the square from (i, j) to (i + 1, j + 1).

Example:

f = linear_interpolation()
print(f(1000, 500))

f_grad = linear_interpolation(grad=True)
z, (gx, gy) = f_grad(1000, 500)
print(f"Height: {z:.2f} m, gradient: ({gx:.2f} m/m, {gy:.2f} m/m)")

nevis.spline(verbose=False)

Returns a spline interpolation over the full GB data set.

The returned function takes two arguments x and y (both in metres) and returns an interpolated height z (in meters).

Example:

f = spline()
print(f(1000, 500))

Notice: Calling this method will result in the creation and storage of a very large cache file in the nevis data directory.