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Pressure Measurement: Difference between revisions
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==Setting the Datum==
All weather stations allow you to adjust the pressure for sea level. You should not make the adjustment within Cumulus.
For Fine Offset see [[FAQ#Cumulus_doesn.E2.80.99t_show_the_same_pressure_as_my_Fine_Offset_console]]. On a Fine Offset station, the pressure measured at the station is called Absolute Pressure, and the pressure corrected to sea level is called Relative Pressure, and the console displays the characters "rel" when it is displaying Relative Pressure. It is therefore the Relative Pressure reading which you need to adjust so that is displaying the current sea-level pressure for your location.▼
The best way to get MSL (sea level) pressure at your location is to go to a site like [http://www.wunderground.com/ Weather Underground] and enter your location. It will find a weather station nearby and give you the current MSL pressure.
Alternatively, look at a isobar chart at a site like [http://www.meteorologica.info/UKisobars.htm weather superstore], and interpolate for your location. You can be sure this uses sea level values.
The best time to set your datum is when the pressure is not changing either with time or between nearby locations. Note most sites only give pressure to the nearest hPa, and airport METAR (except when reported in tenths) always rounds down, so you can be 0.
▲For Fine Offset clones, see [[FAQ#Cumulus_doesn.E2.80.99t_show_the_same_pressure_as_my_Fine_Offset_console]]. On a Fine Offset station, the pressure measured at the station is called Absolute Pressure, and the pressure corrected to sea level is called Relative Pressure, and the console displays the characters "rel" when it is displaying Relative Pressure. It is therefore the Relative Pressure reading which you
==How Accurate are PWS Barometers?==
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