Knowledge Base
KestrelMet 6000 Barometric Pressure Accuracy, Calculations, & CWOP MADIS Checks
Every KestrelMet weather station is checked against a precision NIST-traceable reference pressure sensor in our manufacturing process at the Boothwyn PA plant, and the pressure sensors that we use in the KestrelMet 6000 exhibit minimal drift over the 2-year warranty period. For these reasons, we have not engineered a pressure calibration interface for the KestrelMet 6000.
To compare pressure conditions from one location to another, meteorologists correct pressure to sea-level conditions. Because the air pressure decreases as you rise in altitude, the sea-level corrected pressure (the pressure your location would be at if located at sea-level) is generally higher than your measured pressure.
Thus, your absolute pressure may read 28.62 inHg (969 mb) at an altitude of 1000 feet (305 m), but the relative pressure is 30.00 inHg (1016 mb).
The standard sea-level pressure is 29.92 inHg (1013 mb). This is the average sea-level pressure around the world. Relative pressure measurements greater than 29.92 inHg (1013 mb) are considered high pressure and relative pressure measurements less than 29.92 inHg are considered low pressure.
The pressure measurement displayed on AWN is relative pressure. To determine the relative pressure for your location, AWN locates an official reporting station near you, and sets your weather station relative pressure calculation parameters to match the official reporting station. Note that absolute pressure and relative pressure are both included when station data is downloaded.
Pressure details for CWOP MADIS L3 spatial failures:
Based on experience, MADIS failures come and go and are not necessarily an indicator that there is anything out of calibration, especially when barometric pressure is the measurement in question. For MADIS L3 spatial failures, it is very unlikely that your pressure sensor is the cause. This forum thread provides some useful perspectives on the L3 spatial failure, including one user who tried recalibrating their pressure sensor seasonally in an attempt to make the L3 error go away:
https://groups.io/g/wxqc/topic/chasing_the_calibration_tail/21375996
If you have already confirmed that you are sending the correct altitude to CWOP, then it may be one of the nearby stations that is causing the L3 error. Alternatively, you could try changing the altitude in the CWOP interface which will effectively adjust the relative pressure calculated by CWOP.