Thanks for the input Paul, I believe your are correct. As soon as you see Rel Offset being calculated as an altitude only offset it is pretty clear it is altimeter and that means the pressure you are offsetting from must be pressure. I am not sure why I put down barometer, perhaps it was the liberal of the word barometer throughout the Ecowitt calibration instructions.Will be fixed in b8.
One nagging thought I have have had this afternoon is what pressure value is the GW1000 uploading to WU, WU expects what WeeWX calls barometer but on the face of it that is the one pressure value the GW1000 does not have. I did set my GW1000 to do a customised upload in WU protocol to one of my VMs and it included fields named baromabsin and baromrelin being the two GW1000 pressure values in inches Hg. If I had the time I would intercept the GW1000 actual upload to WU but I somehow suspect it will be the same. Gary On Thursday, 30 July 2020 10:50:16 UTC+10, Paul Anderson wrote: > > Should we map 'altimeter': 'relbarometer' ? > > Gw1000 produces 2 pressure readings: > As defined by Ecowitt Calibration of barometric pressure settings > <http://www.ecowitt.com/news/102.html> > *Absolute Pressure* > "Absolute barometric pressure, can be calibrated at manufacturing time by > comparing with a precise instrument that measures pressure at the same > location. In practice, sometimes small adjustments of a few hPa may be > needed" > *Relative Pressure* > "The relative pressure represents what the air pressure would indicate if > your station was at sea level and depends on the altitude of your console > and cannot be known in advance. This is why it needs an adjustment" > > If you work your way thru there cal procedure you will see that you use > the WS View app to set 2 offsets: > Abs Offset > Rel Offset > To set Rel Offset they have you determine station elevation and direct you > to a site that produces a offset based solely on elevation. So *Rel > Offset* is a *STATIC *offset applied against your Absolute Pressure. It > never changes if we set a Rel Offset of 6.0 hPa then Relative Pressure will > always read 6.0 hPa higher than Absolute Pressure. > As we see in WeeWX Wiki > > Station or Gauge Pressure (key *pressure*): This is the absolute, raw > pressure as measured by your instrument. It is not corrected for altitude > or pressure. Pilots call this QFE > Sea-level Pressure (*barometer*): This is the pressure corrected for > altitude, temperature, and (frequently) humidity. Pilots call this QFF. > This is the value displayed by the standard skin. > Altimeter Pressure (*altimeter*) : This is the pressure corrected for > altitude, using a standard temperature profile. Pilots call this QNH. > > Because we are on a very limited device which does not attempt in any way > to apply a temperature compensation I believe that mapping 'altimeter': > 'relbarometer' may be more appropriate. StdWXCalculate will calculate > barometer for us when it appears in a template. > Thanks > Paul > > >> >> You received this message because you are subscribed to the Google Groups >> "weewx-user" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to weewx-user+unsubscr...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/weewx-user/F82E7D44-2090-4C09-9BA6-8355FE73841F%40gmail.com >> . >> > -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to weewx-user+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/weewx-user/a9efe943-d23e-4458-b475-3daed4d3cac5o%40googlegroups.com.
