Barometric sensor and altitude determination accuracy

In October 2019, the FCC introduced a regulation to supply floor level information for emergency calls. To achieve this goal, the FCC agreed on a directive that requires all emergency calls to ensure 3 m z-axis accuracy. Barometric measurements are the most promising method to estimate the altitude, especially in high-rise buildings. US network operators have adopted barometric sensor based technologies to meet the requirements of the new directive.

The directive requires all mobile devices in a network to be certified and fulfil FCC specifications. Currently, in many mobile devices the barometric pressure performance is low and does not meet the strict FCC regulations. Therefore, many devices are highly susceptible to z-axis performance.

To sell mobile devices in the United States, suppliers have to make sure that they fulfil this directive. All mobile network carriers in the Unites States are requested to self-certify compliance of their devices or have them tested at validated test houses.

Is the FP3 certified for this? I am not aware of a similar regulation required in Europe.

Source: Barometric performance testing for carrier acceptance and standalone R&D | Rohde & Schwarz


Interesting and potentially life saving but why then is my phone recording an altitude 73m higher than it should be? My last phone was 46m out and was the devil to sort out how much because I lived in the mountains, now I live near the sea.

Was it not checked because I live in Europe or is every supplier ignoring the regulation?

There is a website somewhere that gives altitude according to location on a map but I do not remember it - wasn’t too difficult to non-google search the site.

How are you checking this in your phone? I still have a FP2. No barometric sensor in FP2, AFAIK. Anybody checked the FP4?

I don’t see any sign of a barometer on the FP3 (I’m not saying there isn’t one but it’s not listed in the equipment test). And FP3 does not appear in this list (though I’ve no idea of how dependable the list is).
The trouble with deriving absolute altitude from barometric pressure is you need frequent calibration, since atmospheric pressure is constantly changing. It’s fine for measuring relative change, but I would have thought not so hot for absolute altitude.
Would not GPS be more accurate? Though, if we’re talking which floor in a skyscraper, admittedly may not work indoors! :wink:

[Edit] Apparently GPS would not be more accurate than modern barometric sensors. I’d no idea they’d made such progress, see this.


Could have been a little premature with the question as most apps seem to rely on GPS for height? Wish GPS was that good but it isn’t.
To some extent there seems to be a problem everywhere with height measurement. Mine stems from using OSMand free sat nav app based on Open Street Maps. However there was a difference between known heights on my last phone (LG) and this one the Fairphone 3+ for the same software. I assumed it was a calibration error of some sort.
Catching up on technology and checking out different apps which all give different readings and values it appears there are barometric sensors and GPS at play. If it is important it is really worth following up how your device works and accuracy. For these people you need calibrated barometric pressure and satellite gps, all of which requires some proper understanding etc?
In my case it helps when house hunting away from the coast in Spain as away of knowing what climatic conditions to expect - as well as studying the local fauna and flora.
Anyway, I looked at some so called ‘top apps’ and easily got a range of 60 to 80m high using GPS. However, one app said 11 metres! Now, I am near the sea ( I can see it 500m away) and have already made a rough measurement - a value of 21m. I was well pleased with that when I used a map system I found on a web site (sorry, it was not important enough to bookmark) that said 18m.
So the app has a calibration feature too and appeared to be the only one that does. it was really fiddly to set but a meter or two doesn’t hurt unless you are a pilot? :slight_smile: It was called Altimeter Free and I found it on Aptoide App site for those of us that are averse to Google Play Store.
Hope this is useful, good luck!

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