I have one question for you experienced friends, the WH3000 is showing absolute and relative Air pressure..but how does it determine the difference between the two ?
Shouldn t be the reading the same on the coast?
Thank you
The station has no idea that you are on the coast (at sea level). If your Relative offset is configured such that it is different than Absolute pressure then that is what it is set for. By changing the Relative Offset you have essentially told the station that you are at a different elevation than sea level if your offset is not zero. Offset means difference between Relative and Absolute.
Also I think I found your WU ID and it is IPOVLJ1 so you've got a typo in your post.
You are also at 21 meters of elevation despite being at the coast. That is enough elevation for the difference between Absolute and Relative pressure to differ by 2.5 hPa.
I'm going by your WU elevation settings. But if I use FreeMapTools elevation finder and use you actual map location you seem to actually be at an elevation of 5 meters.
https://www.freemaptools.com/elevation-finder.htmTherefore I don't know which is correct. Is the elevation of 21 meters correct? Or is the WU map location correct which corresponds to 5 meters according to FreeMapTools?
Even 5 meters of elevation would contribute a difference of 0.6 hPa between Absolute and Relative.
In WU when configuring a station ID, you enter in the elevation of the barometric sensor, not the elevation of your outdoor sensor array. Same thing for WeeWX.
You should not use the direct elevation indicated by FreeMapTools, because you need to also consider the height of the console above ground level. FreeMapTools is only giving you ground elevation. This may make the difference of at least another meter or more if your console is on a 2nd floor. Remember the barometer is inside of the display for your station and not part of the outdoor sensor array.
On your station:
Changing Relative is effecting an elevation adjustment.
Changing Absolute is effecting a calibration if the factory calibration is not adequate.
This happens because these station were not designed to have a place to enter in your elevation unfortunately. By you making Absolute and Relative different from each other is how you essentially give the station your elevation. You have to do some math to know what the barometric difference is for a given elevation. For doing the math I use this site:
https://keisan.casio.com/exec/system/1224579725It is important to not change the starting pressure of 1013.25 and to also not change the temperature of 15°C because we need to calculate a standard offset that would work as an average offset.