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I was really hoping for a barometer so I could recruit iOS users to pressureNET. No such luck. Maybe next time.
by cryptoz 14y ago
I was really hoping for a barometer so I could recruit iOS users to pressureNET. No such luck. Maybe next time.
- deleted 14y ago[deleted]
- mladenkovacevic 14y agoYes I think you're the cat I was looking for! I recently got a Galaxy Nexus and I remember reading here a while ago about your app that crowd sources barometer readings from phones that have it but I couldn't remember what it was called when I got the GNex. I'll go sign up. Thanks.
- pennig 14y agoOh. You were serious. I feel bad for laughing now.
- jrockway 14y agoYeah, what a loser for collecting weather information... ?
- nostromo 14y agoCool project dude! But why on Earth does any phone ship with a barometer? Weather is the only application I can think of, and surely it's easier just to pull weather conditions from the network.
- pndmnm 14y agoMEMS barometers are commonly used for relative altimetry (e.g. stair climb calculations on activity trackers, etc).
- jlgreco 14y agoHow accurate are they for relative altimetry indoors? I could imagine climate control throwing in a decent margin of error if all the inputs/outputs (vents and blowers?) aren't balanced correctly. Edit: They probably carry barometers already, but AC installer people could make use of phones with this hardware.
- mikeash 14y agoI don't think HVAC systems will do much damage there. I have a gadget on my airplane that gives altitude accurate to the foot, and that's while moving 60MPH or more through potentially turbulent air.
- jlgreco 14y agoI am thinking more about actual differences in atmospheric pressure between indoors and outdoors, or even between rooms in a building. If the ventilation system is installed correctly this shouldn't happen, but if it is not then you can cause either an overpressure or underpressure in the building.
- mikeash 14y agoI don't think buildings will sustain much of a pressure difference. For example, a 10ft-equivalent pressure difference will exert a roughly 16 pound force on a standard residential door, which would be highly noticeable, and it's probably tough to seal a building well enough to contain that kind of pressure.
- jlgreco 14y agoHmm, I had no idea that pressure differences between altitudes were that great. Fair enough.
- deleted 14y ago[deleted]
- ConstantineXVI 14y agoIt's mainly[0] to give the phone/tablet a rough altitude reading to make GPS locks faster. [0] https://plus.google.com/112413860260589530492/posts/jVJhPyouWDP https://plus.google.com/112413860260589530492/posts/jVJhPyou... EDIT: relevant thread
- mikeash 14y agoThat makes no sense. My iPhone takes two seconds to get a solid GPS lock and it doesn't have a barometer. My stand-alone TomTom car GPS takes about 30 seconds to get a lock from a cold start, which is entirely attributable to the time required to download the satellite positions over the extremely slow 70s-era channel that they're broadcast over. Actually solving the equations takes no appreciable time on anything resembling modern hardware. As far as I know, aGPS as found on modern devices is all about getting that almanac faster (which is why my iPhone only requires two seconds), not about using a rough fix to then get a better fix. I realize that isn't your post, but it seemed appropriate to reply here since you posted the link.
- archivator 14y agoA-GPS is about downloading the almanac over the fast ground data link. Solving the equations for partial signals is DIFFICULT and is where most innovation is these days. Your phone takes two seconds (and so does mine) probably because you have WiFi on and you live in the States. Try living in the middle of nowhere in, say, Serbia, and see how fast you get a lock, regardless of WiFi.
- mikeash 14y agoExcept that my years-old TomTom can figure out my location as fast as it can download the almanac. Clearly the equation-solving part is not a limiting factor there.
- calciphus 14y agoMany android devices support actual GPS, not just aGPS, so you can use them in places where you have no cell signal (say, while hiking). Your iPhone takes 2 seconds because it's never a cold start. You're always connected to at least one cell tower you know the location of, you have several nearby wifi access points, etc. It might not be a feature you need for your limited use case. Cool. Then you won't miss it.
- cheald 14y agoThey're very useful for fine-tuning altitude readings.
- PanMan 14y agoAltitude measurements. My (standalone) GPS 10 years ago had it as one of its main features. The extra hardware needed on a phone can't be that much.
- mikeash 14y agoGPS gives you altitude already, no need for a barometer. It's not hugely accurate, but it's more accurate than an uncalibrated altimeter.
- PanMan 14y agobut a properly calibrated barometer is WAY more accurate than GPS. 10 years ago I could track a two meters offset (that's the difference between your head and your feet!).
- mikeash 14y agoIndeed, but I can't think of any way to calibrate the thing other than looking up your location and pulling down weather data, or simply forcing the user to put in an altimeter setting.
- pkulak 14y agoSo it knows when you change floors for indoor maps?