Thanks for all this, I'll go read some more about that. I remember reading a book, a novel, but they were describing how an airport had to quote their bm pressure on the ground and their altitude to feed into the aircrafts device to give an accurate value before trying a landing, especially by instruments.
I don't know how far weather can effect pressure and how much pressure changes with altitude to see the scale of the issue. How many millibars per hundred feet of altitude for example, I'm sure 20 or 30 millibars of variability isn't unusual for weather. RobH. ----- Original Message ----- From: "Sieghard Weitzel" <siegh...@live.ca> To: <viphone@googlegroups.com> Sent: Monday, October 06, 2014 6:34 PM Subject: RE: Curious about the barometer in iPhone 6? Hi Rob and Jan, Altimeters both stand-alone units sold in climbing and outdoor stores as well as those integrated in all of the better Garmin GPS units all use a barometric sensor to give precise elevation readings. Any GPS as well as the iPhone can give you elevation based on GPS information, but while this is better now than it was years ago, it is still less accurate than elevation information based on barometric pressure because of GPS signal time delays and simply the problem with acquiring enough satellites for an accurate calculation. . Typically all one has to do with a barometric altimeter is set the elevation at a known location, e.g. any airport would do because you can simply ask the airport authorities or google what the elevation of any particular airport is. Once set a barometric altimeter will give you accurate readings as you go up or down in elevation based on air pressure. This is the same principal as in scuba diving where you get very accurate depth readings from your depth gauge based on water pressure, pressure at sea level is 1 bar or approx. 14.5 pounds per square inch and this increases by 1 bar or 14.5 pounds per square inch for every 33 feet you go down and the depth gauge messures this pressure and gives your depth in return. A relatively deep recreational dive of 110 feet means you are exposed to 4 Bar or approx. 58 pounds per square inch of pressure. If you take an empty 2 Liter pop bottle down there with the cap screwed on tight it will be squished flat. You will have to recalibrate a barometric altimeter if there are significant changes in air pressure due to weather conditions, e.g. a storm causes an intense low pressure system. If you want to learn more about this all you have to do is Google something like "How does a barometric altimeter work" or "How ddo weather conditions effect barometric altimeters" or "How to calibrate a barometric altimeter". Regards, Sieghard -----Original Message----- From: viphone@googlegroups.com [mailto:viphone@googlegroups.com] On Behalf Of Jan Kleinhans Sent: Monday, October 06, 2014 12:13 AM To: viphone@googlegroups.com Subject: Re: Curious about the barometer in iPhone 6? Hi Thanks for this. It is interesting indeed. I read the altitude thing in a review of the iPhone 6 on the gsm arena website, and also did not quite get it how that would help, so that's why I was wondering if the barometer was usable for it real function via voice over? Thanks all the same. Jan ----- Original Message ----- From: "RobH." <bobs...@googlemail.com> To: <viphone@googlegroups.com> Sent: Monday, October 06, 2014 9:00 AM Subject: Re: Curious about the barometer in iPhone 6? This is interesting, though don't see how it would help with height/altitude. Given the variability of air pressure relative to weather conditions, it would hardly be accurate. Even planes used to have to zero their altimeter relative to prevailing conditions before they get a good or accurate fix. Modern ones probably do better now. And after all that, Siri can work that out with GPS, too. RobH. Disappointed, Siri gave me a lecture on what altitude was, and didn't tell me my position at all. Yet I have been, when using 6.1.4 or whatever that was. ----- Original Message ----- From: "Jan Kleinhans" <jhkleinh...@telkomsa.net> To: <viphone@googlegroups.com> Sent: Monday, October 06, 2014 4:32 AM Subject: Curious about the barometer in iPhone 6? Hi Has anybody that owns a iPhone 6 or 6+ looked at the barometer function of the phone? I am curious as to whether it can be used by users using voice over? I read somewhere that it is used mainly for elevation, but I am interested in the weather functions of the barometer, meaning can one get a reading in inches or milibars like a normal barometer used in weather stations? Regards Jan Kleinhans -- The following information is important for all members of the viphone list. All new members to the this list are moderated by default. If you have any questions or concerns about the running of this list, or if you feel that a member's post is inappropriate, please contact the owners or moderators directly rather than posting on the list itself. The archives for this list can be searched at http://www.mail-archive.com/viphone@googlegroups.com/. --- You received this message because you are subscribed to the Google Groups "VIPhone" group. To unsubscribe from this group and stop receiving emails from it, send an email to viphone+unsubscr...@googlegroups.com. To post to this group, send email to viphone@googlegroups.com. 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