convertbng

0.7.11 verified Fri May 01 auth: no python

Convert latitude/longitude to and from British National Grid (OSGB36) / ETRS89 coordinates using the OS OSTN15 transform. The library is powered by Rust FFI for high performance. Current version 0.7.11, requires Python >=3.10. Released irregularly.

pip install convertbng

Common errors

error ImportError: No module named 'convertbng.util' ↓

cause Incorrect import path; users try `from convertbng import convert_lonlat_to_bng`.

fix

Use from convertbng.util import convert_lonlat_to_bng.

error TypeError: float() argument must be a string or a number, not 'list' ↓

cause Passing a Python list directly instead of a numpy array.

fix

Wrap inputs in numpy arrays: np.array(lons, dtype=np.float64).

error ValueError: Buffer dtype mismatch, expected 'float64' but got 'float32' ↓

cause Input array dtype is float32; the Rust backend expects float64.

fix

Cast arrays to float64: arr.astype(np.float64).

Warnings

breaking Installation may require Rust toolchain (rustc and cargo) if no precompiled wheel is available for your platform. This can cause cryptic errors on some systems. ↓

fix Install Rust via https://rustup.rs/ or use a conda-forge build: conda install -c conda-forge convertbng

gotcha Input must be numpy arrays of float64 type. Passing lists or other dtypes will raise TypeError or produce wrong results. ↓

fix Always convert inputs to numpy arrays: np.array(values, dtype=np.float64)

gotcha Coordinates outside the British National Grid coverage area (approx. 49°N–61°N, 8°W–2°E) will return NaN. Error handling not built-in; check for NaN yourself. ↓

fix Validate results using np.isnan(easting) or similar.

Imports

convert_lonlat_to_bng

wrong

from convertbng import convert_lonlat_to_bng

correct

from convertbng.util import convert_lonlat_to_bng

Functions are in convertbng.util, not top-level.

convert_bng_to_lonlat

wrong

from convertbng import convert_bng_to_lonlat

correct

from convertbng.util import convert_bng_to_lonlat

Functions are in convertbng.util, not top-level.

Quickstart

Convert between longitude/latitude and British National Grid coordinates. Inputs must be numpy arrays.

import numpy as np
from convertbng.util import convert_lonlat_to_bng, convert_bng_to_lonlat

# Example coordinates (lon, lat)
lon = np.array([-0.1276, -2.0])
lat = np.array([51.5074, 53.0])

# Convert to BNG (returns (easting, northing) tuple of numpy arrays)
easting, northing = convert_lonlat_to_bng(lon, lat)
print(easting, northing)

# Convert back to lon/lat
lon_back, lat_back = convert_bng_to_lonlat(easting, northing)
print(lon_back, lat_back)