Bidirectional UTM-WGS84 converter for python

>>> import utm

Convert a (latitude, longitude) tuple into an UTM coordinate:

>>> utm.from_latlon(51.2, 7.5)
(395201.3103811303, 5673135.241182375, 32, 'U')

The syntax is utm.from_latlon(LATITUDE, LONGITUDE).

The return has the form (EASTING, NORTHING, ZONE_NUMBER, ZONE_LETTER).

You can also use NumPy arrays for LATITUDE and LONGITUDE. In the result EASTING and NORTHING will have the same shape. ZONE_NUMBER and ZONE_LETTER are scalars and will be calculated for the first point of the input. All other points will be set into the same UTM zone. Therefore it's a good idea to make sure all points are near each other.

>>> utm.from_latlon(np.array([51.2, 49.0]), np.array([7.5, 8.4]))
(array([395201.31038113, 456114.59586214]),
 array([5673135.24118237, 5427629.20426126]),
 32,
 'U')

Convert an UTM coordinate into a (latitude, longitude) tuple:

>>> utm.to_latlon(340000, 5710000, 32, 'U')
(51.51852098408468, 6.693872395145327)

The syntax is utm.to_latlon(EASTING, NORTHING, ZONE_NUMBER, ZONE_LETTER).

The return has the form (LATITUDE, LONGITUDE).

You can also use NumPy arrays for EASTING and NORTHING. In the result LATITUDE and LONGITUDE will have the same shape. ZONE_NUMBER and ZONE_LETTER are scalars.

>>> utm.to_latlon(np.array([395200, 456100]), np.array([5673100, 5427600]), 32, 'U')
(array([51.19968297, 48.99973627]), array([7.49999141, 8.3998036 ]))

Since the zone letter is not strictly needed for the conversion you may also the northern parameter instead, which is a named parameter and can be set to either True or False. Have a look at the unit tests to see how it can be used.

The UTM coordinate system is explained on this Wikipedia page.

The library has been compared to the more generic pyproj library by running the unit test suite through pyproj instead of utm. These are the results:

• with pyproj (without projection cache): 4.0 - 4.5 sec
• with pyproj (with projection cache): 0.9 - 1.0 sec
• with utm: 0.4 - 0.5 sec

NumPy arrays bring another speed improvement (on a different computer than the previous test). Using utm.from_latlon(x, y) to convert one million points:

• one million calls (x and y are floats): 1,000,000 × 90µs = 90s
• one call (x and y are numpy arrays of one million points): 0.26s

Create a new virtualenv and install the library via pip install -e .. After that install the pytest package via pip install pytest and run the unit test suite by calling pytest.

see CHANGELOG.rst file

• Bart van Andel <[email protected]>
• Tobias Bieniek <[email protected]>
• Torstein I. Bø

Copyright (C) 2012 Tobias Bieniek <[email protected]>

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