pywws.calib
Calibrate raw weather station data
This module allows adjustment of raw data from the weather station as part of the ‘processing’ step (see pywws.process). For example, if you have fitted a funnel to double your rain gauge’s collection area, you can write a calibration routine to double the rain value.
The default calibration generates the relative atmospheric pressure. Any user calibration you write must also do this.
Writing your calibration module
Firstly, decide where you want to keep your module. Like your text and
graph templates, it’s best to keep it separate from the pywws code, so
it isn’t affected by pywws upgrades. I suggest creating a modules
directory in the same place as your templates
directory.
You could start by copying one of the example calibration modules, or
you can create a plain text file in your modules
directory, e.g.
calib.py
and copy the following text into it:
class Calib(object):
def __init__(self, params, stored_data):
self.pressure_offset = float(params.get('config', 'pressure offset'))
def calib(self, raw):
result = dict(raw)
# calculate relative pressure
result['rel_pressure'] = result['abs_pressure'] + self.pressure_offset
return result
The Calib
class has two methods. Calib.__init__()
is
the constructor and is a good place to set any constants you need. It
is passed a reference to the raw data storage which can be useful for
advanced tasks such as spike removal. Calib.calib()
generates
a single set of ‘calibrated’ data from a single set of ‘raw’ data.
There are a few rules to follow when writing this method:
Make sure you include the line
result = dict(raw)
, which copies all the raw data to your result value, at the start.Don’t modify any of the raw data.
Make sure you set
result['rel_pressure']
.Don’t forget to
return
the result at the end.
When you’ve finished writing your calibration module you can get pywws
to use it by putting its location in your weather.ini
file. It
goes in the [paths]
section, as shown in the example below:
[paths]
work = /tmp/weather
templates = /home/jim/weather/templates/
graph_templates = /home/jim/weather/graph_templates/
user_calib = /home/jim/weather/modules/usercalib
Note that the user_calib
value need not include the .py
at the
end of the file name.
Classes
|
Calibration class that implements default or user calibration. |
|
Default calibration class. |
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