Source code for pywws.conversions

#!/usr/bin/env python

# pywws - Python software for USB Wireless Weather Stations
# http://github.com/jim-easterbrook/pywws
# Copyright (C) 2008-13  Jim Easterbrook  jim@jim-easterbrook.me.uk

# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

"""conversions.py - a set of functions to convert pywws native units
(Centigrade, mm, m/s, hPa) to other popular units

"""

# rename imports to prevent them being imported when
# doing 'from pywws.conversions import *'
from pywws import Localisation as _Localisation

[docs]def illuminance_wm2(lux): "Approximate conversion of illuminance in lux to solar radiation in W/m2" if lux is None: return None return lux * 0.005
[docs]def pressure_inhg(hPa): "Convert pressure from hectopascals/millibar to inches of mercury" if hPa is None: return None return hPa / 33.86389
[docs]def rain_inch(mm): "Convert rainfall from millimetres to inches" if mm is None: return None return mm / 25.4
[docs]def temp_f(c): "Convert temperature from Celsius to Fahrenheit" if c is None: return None return (c * 9.0 / 5.0) + 32.0
[docs]def winddir_degrees(pts): "Convert wind direction from 0..15 to degrees" if pts is None: return None return pts * 22.5
_winddir_text_array = None
[docs]def winddir_text(pts): "Convert wind direction from 0..15 to compass point text" global _winddir_text_array if pts is None: return None if not _winddir_text_array: _ = _Localisation.translation.gettext _winddir_text_array = ( _('N'), _('NNE'), _('NE'), _('ENE'), _('E'), _('ESE'), _('SE'), _('SSE'), _('S'), _('SSW'), _('SW'), _('WSW'), _('W'), _('WNW'), _('NW'), _('NNW'), ) return _winddir_text_array[pts]
[docs]def wind_kmph(ms): "Convert wind from metres per second to kilometres per hour" if ms is None: return None return ms * 3.6
[docs]def wind_mph(ms): "Convert wind from metres per second to miles per hour" if ms is None: return None return ms * 3.6 / 1.609344
[docs]def wind_kn(ms): "Convert wind from metres per second to knots" if ms is None: return None return ms * 3.6 / 1.852
_bft_threshold = ( 0.3, 1.5, 3.4, 5.4, 7.9, 10.7, 13.8, 17.1, 20.7, 24.4, 28.4, 32.6)
[docs]def wind_bft(ms): "Convert wind from metres per second to Beaufort scale" if ms is None: return None for bft in range(len(_bft_threshold)): if ms < _bft_threshold[bft]: return bft return len(_bft_threshold)
[docs]def cadhumidex(temp, humidity): "Calculate Humidity Index as per Canadian Weather Standards" if temp is None or humidity is None: return None # Formulas are adapted to not use e^(...) with no appreciable # change in accuracy (0.0227%) saturation_pressure = (6.112 * (10.0**(7.5 * temp / (237.7 + temp))) * float(humidity) / 100.0) return temp + (0.555 * (saturation_pressure - 10.0))
def _main(argv=None): global _winddir_text_array # run some simple tests print 'Wind speed:' print '%6s %8s %8s %8s %6s' % ('m/s', 'km/h', 'mph', 'knots', 'bft') for ms in (0, 1, 2, 4, 6, 9, 12, 15, 18, 22, 26, 30, 34): print '%6g %8.3f %8.3f %8.3f %6d' % ( ms, wind_kmph(ms), wind_mph(ms), wind_kn(ms), wind_bft(ms)) print 'Wind direction:' for pts in range(16): print winddir_text(pts), print print 'Wind direction, in Swedish:' _Localisation.SetTranslation('sv') _winddir_text_array = None for pts in range(16): print winddir_text(pts), print if __name__ == "__main__": _main()