Manual barometer calibration

So you must have a couple of PhDs to make this damned altimetry to work... ridiculous...

Why not just get the QNH from the local airport? This way you don't have to mess around with making corrections. 

To be honest, you shouldn't be using the barometer / altimeter in the watch for flying anyway because it'll have a significant error based on the fact that it's referenced static pressure inside the cabin.

For exercise or activities it's elevation change that's important, and it really doesn't matter what reference you start from provided it doesn't change throughout the activity.

I agree -  its just that I am trying to get the darned thing to read out the current QFE or QNH before going to the aircraft - that info is useful in some of the flight profiles we undertake.

For instance, I have an android phone - Samsung Note 8 with an accurate baro sensor. I have an app that reads the raw actual pressure from the phone sensor and gives the readout - which is the QFE (if one is at the airport).

Re- using QFE to calibrate - the METAR broadcast with QNH is hourly and the value changes during the hour. Usually I walk across to the Met section or ask the chappie on duty the exact reading of the baro to the first decimal - I use that for the calibration. 

If the phone with the baro sensor can, then why can't Garmin just enable that option - a direct readout of the actual pressure?  its a useful bit of info to have for some aviators.

The barometer works perfectly in unpressurised aircraft. I use it in my CAP10. I look at the aviation weather, get the local QNH (which is based on mean sea level) and set the altimeter to the known airfield altitude and it all just works. Make sure you set the watch in altimeter mode and disable auto mode inside/outside of activities and then the altimeter will work directly from pressure changes. Obviously if the local pressure changes (as it does), your altitude read out will change as a result.

Just like in an aircraft as you fly around, you get the local QNH from ATIS, or ATC and adjust your barimetric altimeter, you also have to adjust the watch.

To be honest if all you are looking for is a delta change, rather than an accurate altitude reading then it doesnt matter what the pressure is set to, just set the altimeter to what ever you want, as you move up or down the pressure changes will be reflected in the altitude.

Chopper Pilot said:

If the phone with the baro sensor can, then why can't Garmin just enable that option - a direct readout of the actual pressure?  its a useful bit of info to have for some aviators.

Garmin calls the unadjusted pressure "Ambient Pressure."  It is available as a Data Field for use in an Activity, or as a Widget such as this one: Ambient Pressure Widget from CIQ Store

FYI

Gaijin,

Thank you very much indeed! That nifty little widget solves the problem.

I have come across some of your responses in other threads - you indeed are The Zen Master!

Thanks once again!!

I think you also mentioned earlier that you were having problems with the altitude being recalibrated back to the previous GPS altitude while in an activity.  Since you need to be in an activity to display the absolute pressure value, you may have to disable GPS or auto-calibrate, or both during the chosen activity to prevent that from happening again.

BTW, one of the benefits of the Fenix is you can program your own apps, which I have done to create my own barometer app.  It displays the absolute pressure and the SLP, along with the altitude reference you chose to convert the absolute pressure to SLP on one screen.  I could e-mail you the file, PM me if interested.

5693709 said:

BTW, one of the benefits of the Fenix is you can program your own apps, which I have done to create my own barometer app.  It displays the absolute pressure and the SLP, along with the altitude reference you chose to convert the absolute pressure to SLP on one screen.  I could e-mail you the file, PM me if interested.

Do you mean a Data Screen in an Application configured something like this?

Elev in ft, Press in InHg.

If so, then no special programming necessary - just formatting Data Fields.

Or am I missing something?

HTH

that's similar, but not quite the same thing as what I did.  I think one of the issues I remember running into was the ambient pressure would display with 4 digits, so if it was under 1000mb you'd get 0.1mb resolution, but above 1000mb it was 1mb resolution.  I wanted 0.1mb resolution all the time.  Another issue is going back/forth from altimeter mode to barometer mode to and locking the altitude when I wanted a barometer, etc. got to be a pain, so the app runs independently of those mode settings.  And it does a few other things I threw in that I didn't mention before, like store a previous barometer setting and calculate how much barometric change occurred over time since you stored last. 

And, one thing that your screen doesn't show is what was the altitude when you calibrated the barometric pressure, not just the current altitude reading.  I guess if you always calibrate it at a known altitude, like your house, then that's not important, but if you are traveling and recalibrate it to different altitudes along the way you don't have to go into the altimeter/barometer widgets to do that.  Its not a whole lot different than what you have, but I think its more convenient to use and provides a bit more information.