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"""!
@package units
@brief Units management
Probably will be replaced by Python SWIG fns in the near future(?)
Usage:
@code
from units import Units
@endcode
Classes:
- BaseUnits
(C) 2009 by the GRASS Development Team
This program is free software under the GNU General Public
License (>=v2). Read the file COPYING that comes with GRASS
for details.
@author Martin Landa <landa.martin gmail.com>
"""
class BaseUnits:
def __init__(self):
self._units = dict()
self._units['length'] = { 0 : { 'key' : 'mu', 'label' : _('map units') },
1 : { 'key' : 'me', 'label' : _('meters') },
2 : { 'key' : 'km', 'label' : _('kilometers') },
3 : { 'key' : 'mi', 'label' : _('miles') },
4 : { 'key' : 'ft', 'label' : _('feet') } }
self._units['area'] = { 0 : { 'key' : 'mu', 'label' : _('sq map units') },
1 : { 'key' : 'me', 'label' : _('sq meters') },
2 : { 'key' : 'km', 'label' : _('sq kilometers') },
3 : { 'key' : 'ar', 'label' : _('acres') },
4 : { 'key' : 'ht', 'label' : _('hectares') } }
def GetUnitsList(self, type):
"""!Get list of units (their labels)
@param type units type ('length' or 'area')
@return list of units labels
"""
result = list()
try:
keys = self._units[type].keys()
keys.sort()
for idx in keys:
result.append(self._units[type][idx]['label'])
except KeyError:
pass
return result
def GetUnitsKey(self, type, index):
"""!Get units key based on index
@param type units type ('length' or 'area')
@param index units index
"""
return self._units[type][index]['key']
def GetUnitsIndex(self, type, key):
"""!Get units index based on key
@param type units type ('length' or 'area')
@param key units key, e.g. 'me' for meters
@return index
"""
for k, u in self._units[type].iteritems():
if u['key'] == key:
return k
return 0
Units = BaseUnits()
def ConvertValue(value, type, units):
"""!Convert value from map units to given units
Inspired by vector/v.to.db/units.c
@param value value to be converted
@param type units type ('length', 'area')
@param unit destination units
"""
# get map units
# TODO
f = 1
if type == 'length':
if units == 'me':
f = 1.0
elif units == 'km':
f = 1.0e-3
elif units == 'mi':
f = 6.21371192237334e-4
elif units == 'ft':
f = 3.28083989501312
else: # -> area
if units == 'me':
f = 1.0
elif units == 'km':
f = 1.0e-6
elif units == 'mi':
f = 3.86102158542446e-7
elif units == 'ft':
f = 10.7639104167097
elif units == 'ar':
f = 2.47105381467165e-4
elif units == 'ht':
f = 1.0e-4
return f * value
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