On October 12th we quietly launched our new Continuous Learning (CL) auto-calibration system for Pressure. The system performs a quality control inspection on the raw station pressure sensor data from your AIR, and applies calibration corrections if needed. Here’s how it works:
The Pressure CL system begins by comparing your AIR’s pressure data to numerous trusted data sources in your immediate area. The data sources are used to define a reference sea level pressure value. The value is then adjusted to an equivalent station pressure using your station’s elevation and AIR’s height above ground level. As a final step, the system will analyze and QC the station pressure, and once confirmed, a calibration is computed and applied to your AIR. Subsequent station pressure observations from your AIR will be governed by this calibration. The system is run every day keeping your pressure data in perfect calibration forever.
Note: if you have made adjustments to your elevation to manually “calibrate” your pressure sensor, please feel free to set it back to the correct value. Doing so will result in odd pressure values at first, but give the CL Pressure system a day or so to run again, and it will fall into line.
If after a day or two your Pressure calibration still seems off, please let us know directly and we’ll dig into your data.
A few notes on Station Pressure versus Sea Level Pressure….
Sea Level Pressure = Barometric Pressure = Relative Pressure = air pressure adjusted to sea level
Station Pressure = Atmospheric Pressure = Absolute Pressure = air pressure measured by the sensor
There are two pressure values reported in the Smart Weather app. One of them is called station pressure - it’s also called “absolute pressure”; or “atmospheric pressure”. This is the value actually measured by the sensor in your AIR. This value is not of much use to people, unless for some reason you want to know what the actual pressure is at your house (maybe for brewing beer or baking bread ?).
The other pressure value reported is “sea level pressure”; - it’s also called “relative pressure” or “barometric pressure”. This value is NOT what the sensor actually measures. Rather, it’s the value that would be measured if you were standing at mean sea level under the same sort of atmospheric conditions at your house. It’s adjusted or “normalized” based on the device’s total height above mean sea level. In the Smart Weather context, the “total height” is the sum of the “elevation” value that you set for your station location and the “height above ground” value that you set for your AIR device.
The value displayed in the main interface of the Smart Weather apps is sea level pressure. Why? Because that’s the most common way to report pressure and it’s the only way to facilitate comparison between locations with different altitudes. This lets you compare apples to apples. This is the value meteorologists care about. This is the value most weather services, websites and apps commonly report. This is also the value that most other home weather stations display. It’s also the value an analog mercury barometer should show.