pypole

pypole is a Python library for simulating and fitting magnetic field maps from magnetic dipole sources. It provides tools for generating synthetic dipole fields, fitting dipoles to measured maps, and processing magnetic field data using FFT-based methods.

Uses NumPy and Numba for fast numerical computation, with JIT-compiled kernels for pixel-level parallelism.

Installation

pypole uses uv for package management.

git clone https://github.com/MikeVolk/pypole.git
cd pypole
uv sync

Quick Start

import numpy as np
from pypole import maps, dipole, fit

# Generate observation grid (100x100 pixels, 1 um pixel size)
x_grid, y_grid = maps.get_grid(pixels=(100, 100), pixel_size=1e-6)

# Generate a random single-dipole source
locations, moments = maps.get_random_sources(n_sources=1)

# Compute the Bz field map (sensor 5 um above sample)
field_map = dipole.calculate_map(x_grid, y_grid, locations, moments, sensor_distance=5e-6)

# Fit a single dipole to the map
p0 = (*locations[0], *moments[0])  # initial guess: (x, y, z, mx, my, mz)
result = fit.fit_dipole(field_map, p0, pixel_size=1e-6)

# Access optimised parameters
print(result.x)   # (x_source, y_source, z_source, mx, my, mz)
print(result.success)

Modules

Conventions

• Dipole parameters are always 6-tuples ordered (x_source, y_source, z_source, mx, my, mz) — positions in metres, moments in Am².
• Coordinate system: NED (North-East-Down). North = -Y axis, +Z points down. Declination is measured CCW from North; 0° = -Y, 90° = +X. Inclination > 0 means pointing downward (+Z).
• fit_dipole returns a scipy.optimize.OptimizeResult — access optimised parameters via .x.

Signal Processing

from pypole import compute

# Upward continue a map by 2 um
continued = compute.upward_continue(field_map, distance=2e-6, pixel_size=1e-6)

# Compute RMS (works on 2D or batched 3D arrays)
rms_value = compute.rms(field_map)

# Compute dipolarity parameter (1 = perfect dipole)
dp = compute.dipolarity_param(field_map, fitted_map)

Coordinate Conversion

from pypole import convert
import numpy as np

# Convert declination/inclination/moment -> x/y/z
dim = np.array([[45.0, 30.0, 1e-14]])   # (dec deg, inc deg, moment Am^2)
xyz = np.zeros((1, 3))
convert.dim2xyz(dim, xyz)

# Convert x/y/z -> declination/inclination/moment
xyz_in = np.array([[1e-14, 0.0, 0.0]])
dim_out = np.zeros((1, 3))
convert.xyz2dim(xyz_in, dim_out)

Development

uv sync                   # install all dependencies (including dev group)
uv run pytest             # run all tests + doctests
make codestyle            # format with ruff (format + fix)
make check-codestyle      # lint check without modifying
make ty                   # type-check with ty
make lint                 # test + check-codestyle + ty
make pre-commit           # run all pre-commit hooks

License

MIT License. See the LICENSE file for details.

Contact

• Email: michaelvolk1979@gmail.com
• GitHub: @MikeVolk