Measurement Units API (Distance and Area)

The measure module allows for convenient representation of distance and area units of measure. [1] The module contains two objects, Distance and Area – both of which may be accessed via the D and A aliases, respectively.

The Distance and Area Objects

Distance objects may be instantiated using a keyword argument indicating the context of the units. In the example below, two different distance objects are instantiated in units of kilometers (km) and miles (mi):

>>> from django.contrib.gis.measure import Distance, D
>>> d1 = Distance(km=5)
>>> print d1
5.0 km
>>> d2 = D(mi=5) # `D` is an alias for `Distance`
>>> print d2
5.0 mi

Conversions are easy, just access the preferred unit attibute name to get a converted distance quantity:

>>> print d1.mi # Converting 5 kilometers to miles
3.10685596119
>>> print d2.km # Converting 5 miles to kilometers
8.04672

Moreover, arithmetic operations may be performed between the distance objects:

>>> print d1 + d2 # Adding 5 miles to 5 kilometers
13.04672 km
>>> print d2 - d1 # Subtracting 5 kilometers from 5 miles
1.89314403881 mi

Two Distance objects multiplied together will yield an Area object, which uses squared units of measure:

>>> a = d1 * d2 # Returns an Area object.
>>> print a
40.2336 sq_km

To determine what the attribute abreviation of a unit is, the unit_attname class method may be used:

>>> print Distance.unit_attname('US Survey Foot')
survey_ft
>>> print Distance.unit_attname('centimeter')
cm

Supported units

Unit Attribute	Full name or alias(es)
km	Kilometre, Kilometer
mi	Mile
m	Meter, Metre
yd	Yard
ft	Foot, Foot (International)
survey_ft	U.S. Foot, US survey foot
inch	Inches
cm	Centimeter
mm	Millimetre, Millimeter
um	Micrometer, Micrometre
british_ft	British foot (Sears 1922)
british_yd	British yard (Sears 1922)
british_chain_sears	British chain (Sears 1922)
indian_yd	Indian yard, Yard (Indian)
sears_yd	Yard (Sears)
clarke_ft	Clarke’s Foot
chain	Chain
chain_benoit	Chain (Benoit)
chain_sears	Chain (Sears)
british_chain_benoit	British chain (Benoit 1895 B)
british_chain_sears_truncated	British chain (Sears 1922 truncated)
gold_coast_ft	Gold Coast foot
link	Link
link_benoit	Link (Benoit)
link_sears	Link (Sears)
clarke_link	Clarke’s link
fathom	Fathom
rod	Rod
nm	Nautical Mile
nm_uk	Nautical Mile (UK)
german_m	German legal metre

Area attributes are the same as Distance attributes, except they are prefixed with sq_ (area units are square in nature).

Footnotes

[1]	Robert Coup is the initial author of the measure objects, and was inspired by Brian Beck’s work in geopy and Geoff Biggs’ PhD work on dimensioned units for robotics.