convertbng 0.3.0

Fast lon, lat to BNG conversion

Fast longitude, latitude to BNG conversion, and vice versa, using a multithreaded Rust binary and FFI.

This module provides two fast methods:

util.convertbng(lons, lats) – pass sequences (such as lists or numpy arrays) of Longitudes and Latitudes, or single values of each. Returns a list of two lists containing Easting and Northing floats, respectively.

util.convertlonlat(eastings, northings) – pass sequences (such as lists or numpy arrays) of Eastings, Northings, or single values of each. Returns a list of two lists containing Longitude and Latitude floats, respectively

And four accurate OSTN02-enabled methods, suitable for surveying and other geodetic work:

Note

The OSTN02-enabled methods are envisaged to be used with accurate measurements collected using the National GPS Network.

convert_osgb36(lons, lats) – convert ETRS89 Longitudes and Latitudes to OSGB36

convert_osgb36_to_lonlat(eastings, northings) – convert OSGB36 Eastings and Northings to ETRS89 longitudes and latitudes

convert_etrs89_to_osgb36(eastings, northings) – convert ETRS89 Eastings and Northings to OSGB36 Eastings and Northings

convert_osgb36_to_etrs89(eastings, northings) – convert OSGB36 eastings and Northings to ETRS89 Eastings and Northings.

All four methods accept and return floating-point numbers.

Warning

Coordinate pairs outside the BNG bounding box will return a result of [[9999], [9999]], which cannot be mapped. Since transformed coordinates are guaranteed to be returned in the same order as the input, it is trivial to check for this value. Alternatively, ensure your data fall within the bounding box before transforming them:

Latitude:

East: 1.768960 (Max)

West: -6.379880 (Min)

Longitude:

North: 55.811741 (Max)

South: 49.871159 (Min)

Installation

Installation as a binary wheel using pip, for OS X:

pip install convertbng

Binary wheels aren’t yet available for Linux or Windows, but installation directly from Github works:

pip install git+git://github.com/urschrei/convertbng.git

Usage

from convertbng.util import convertbng, convertlonlat

# convert a single value
res = convertbng(lon, lat)

# convert lists of longitude and latitude values to BNG Eastings and Northings
lons = [lon1, lon2, lon3]
lats = [lat1, lat2, lat3]
res_list = convertbng(lons, lats)

# convert lists of BNG Eastings and Northings to longitude, latitude
eastings = [easting1, easting2, easting3]
northings = [northing1, northing2, northing3]
res_list_en = convertlonlat(eastings, northings)

# assumes numpy imported as np
lons_np = np.array(lons)
lats_np = np.array(lats)
res_list_np = convertbng(lons_np, lats_np)

Testing

Run nosetests (requires Nose)