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Barometers In iPhones Mean More Crowdsourcing In Weather Forecasts

cryptoz (878581) writes Apple is now adding barometers to its mobile devices: both new iPhones have valuable atmospheric pressure sensors being used for HealthKit (step counting). Since many Android devices have been carrying barometers for years, scientists like Cliff Mass have been using the sensor data to improve weather forecasts. Open source data collection projects like PressureNet on Android automatically collect and send the atmospheric sensor data to researchers.

79 comments

  1. Thus we can settle the debate. by Anonymous Coward · · Score: 0

    This will prove AGW is a proof of theory concept, unavoidably.

    1. Re:Thus we can settle the debate. by Anonymous Coward · · Score: 1

      Quick, everybody leave your phone in the car for an hour. For science.

    2. Re:Thus we can settle the debate. by Anonymous Coward · · Score: 0

      this will emplain weather on iPhones sucking so much.

    3. Re:Thus we can settle the debate. by jshackney · · Score: 2

      Hmm. For work I spend the majority of my time at an approximate cabin altitude of 5,000 to 7,000 feet. I guess my data won't be very meaningful.

    4. Re:Thus we can settle the debate. by ColdWetDog · · Score: 1

      Quick, everybody leave your phone in the car for an hour. For science.

      And then what? Drive up and down a mountain? Drive into a mine shaft?

      You do understand the term 'barometer', do you not?

      --
      Faster! Faster! Faster would be better!
    5. Re:Thus we can settle the debate. by ColdWetDog · · Score: 4, Insightful

      No, it and of itself won't be meaningful. That's the crowdsource bit.

      OK, for all of you that stare at the weatherperson and wonder what the funny lines are for: The column of air just above your head and extending to the top of the atmosphere has a mass that depends on a number of details. This fluctuates from minute to minute and, in fact, occurs in waves (those funny lines). Detailed information about the barometric pressure at any given location and time can be sent to a central station where that data is collected and displayed. The more (accurate) sensors that you have, the better detail and, presumably, the better quality of weather (not climate) forecasting.

      Having lots of barometric pressure measurements attached to a device that can accurately determine location and time can be a useful source of data. For the National Weather Service, the National Security Agency and other fun TLAs. The utility for the weather service is obvious, for the NSA not so much but I believe it has to do with overall conductivity of aluminum foil, or something along those lines.

      --
      Faster! Faster! Faster would be better!
    6. Re:Thus we can settle the debate. by Anonymous Coward · · Score: 0

      OK, for all of you that stare at the weatherperson and wonder what the funny lines are for

      Mostly I just stare at her breasts.

    7. Re:Thus we can settle the debate. by sumdumass · · Score: 1

      No shit. I already have an accurate three day forcast for the home and office. Its called a thermostat and airconditioning.

      What would be nice is a weekend forecast that would say something different than chance of drunkeness, loud music, and women laughing when you ask them to go home with you. Maybe something like dude, she's a he or crowded- stay home and drink or similar. Of course i'm not sure how a barometer would forcast the mangirl problem. Perhaps i should jusr checkand see if my glasses need updating.

    8. Re:Thus we can settle the debate. by Anonymous Coward · · Score: 0

      I don't know if being in a hot car will do anything with pressure, but many high rise buildings (higher pressure) and some sports facilities (lower pressure) have modified atmospheric pressure that could throw off measurements. I remember when I was back in high school we visited the gym of the local university on occasion and opening the doors was quite a challenge because the air pressure was somewhat less than atmospheric as they had a half dozen industrial fans sucking air out of the building to aid in training.

    9. Re:Thus we can settle the debate. by mjwx · · Score: 1

      No, it and of itself won't be meaningful. That's the crowdsource bit.

      None of us are as dumb as all of us.

      Trying to crowd source weather prediction will only result in wildly inaccurate predictions. Many smartphone users work in a climate controlled office... travel there in a climate controlled car from their climate controlled home. So the 5-10 minutes they spend outside wont provide enough data especially if it doesn't have accurate location and elevation data.

      So actual meteorologists will continue to be more reliable than this crowdsoruced application.

      --
      Calling someone a "hater" only means you can not rationally rebut their argument.
  2. And? by blueshift_1 · · Score: 2

    Is this a suprise? I felt like this is a pretty obvious one. I mean, a newsworthy article would be that Apple would then use this data to induce mass climate change and natural disasters where there is a low density of Apple users to increase their market share.

    1. Re:And? by Anonymous Coward · · Score: 0

      Welcome to the 21st Century Apple users! (Android users have been here a while.)

  3. haha by Anonymous Coward · · Score: 0

    "Android devices have been carrying barometers for years"

    Now we see the real purpose of this article.

    1. Re:haha by Wookact · · Score: 4, Funny

      Apples reality distortion field. Remember, its not useful until apple does it, and then once apple does it, it becomes innovation.

    2. Re:haha by Anonymous Coward · · Score: 0

      Be as cynical as you want, but more often than not Apple is usually first with an implementation of a new technology that's actually useful.

      They're not first with everything. They respond to market demands, if a bit slowly and carefully. Big displays on phones for example.

      I'm sure they're not the first phone with a barometric altimeter, but they're the first to put one in a widely device as a standard option, and to back it with an API that makes it easy for any app developer to take advantage of it. (FYI Barometric altimeters have been standard in mid-high end fitness computers like garmin cycling computers for some time. They allow things like quick and easy calculation of elevation change and the the grade of the surface you are riding on)

      They're not the first device maker by far to offer offer fitness sensors and fitness related features in their phones (There are android devices that can talk Ant+. Ant+ is the current standard for wireless fitness device communication but it's quickly being replaced by low power bluetooth) , but they're the first to tie it together in a serious and comprehensive API/package designed to get fitness features in to the hands of all of their users.

      Having a new iphone will mean if you go on a ride or run with your phone, any of the popular fitness services (Strava, endomondo, etc etc) will get better data if you have a new iphone. That's a good thing.

    3. Re:haha by Anonymous Coward · · Score: 0

      Brought to you by the Dept. of Obvious Tautologies!

    4. Re:haha by Anonymous Coward · · Score: 0

      In reality apple phone have also probably had barometers built into them as well, it just probably wasn't enabled for the user to use before. It helps with gps positioning and gives you accurate altitude data. It wouldn't be surprising to hear this is brand new for Apple though, they seem to be 2-3 years behind in terms of following android's trends in tech (big screens, fingerprint reader, multitasking, copy-paste, etc). Apple fans will have IR blasters (every phone should have one!), NFC thats not locked down tight (lol apple pay), and wireless charging (not in some cheesy case, built-in) to look forward to in the next iteration of their beloved iphone.

    5. Re:haha by Anonymous Coward · · Score: 0, Insightful

      That would be true if Android phones weren't YEARS ahead of Apple phones in terms of technology. Tomorrow's must-have feature on your iPhone is today's feature on even basic android phones. Your argument is still essentially "Because Apple does it, its now innovation and genius".

    6. Re:haha by iluvcapra · · Score: 4, Insightful

      "Innovation" mostly has to do with getting people to buy or use something -- actually being the first person to invent or market the thing doesn't really carry any intrinsic benefit, follow-through and execution always trump good ideas. Ideas are cheap.

      --- Signed, Ignaz Semmelweiss, Elija Gray, the Lumiere Brothers, Preston Tucker, Douglas Engelbart, Xerox PARC, inter alia

      --
      Don't blame me, I voted for Baltar.
    7. Re:haha by ColdWetDog · · Score: 1

      I understand most of the other guys, but who is 'Inter Alia"?

      --
      Faster! Faster! Faster would be better!
    8. Re:haha by Anonymous Coward · · Score: 0

      No different than the argument that if Android does it first it's innovative but when Apple does it first it's obvious.
       
      Same fanboy games, different goosesteppers.

    9. Re:haha by Anonymous Coward · · Score: 0

      Thank you for accidentally illustrating why so many people are clueless and incredulous (particularly the so-called "geeks" that frequent here) over Apple's success. You deride things the iphone 6 as being derivative and late yet they smashed industry sales records again, just like with the 5s.

      Lists of features do not make a good product. Being "first" or "ahead" means jack shit. Just because an android phone has something, doesn't mean anyone can take advantage of it. It's the boring, expensive, tedious behind the scenes work to implement said feature that brings success.

      Nobody cared that whatever chinese OEM that made your android phone included a jellybean I2C connected barometric altimeter. Sure, it's there, but the back-end development to make it useful to a large number of app developers was not there. You could not guarantee if there would be one there, what type it was, how it worked, how it performed, etc. Essentially relegated to niche uses and a novelty.

      Now that there is one in /every/ new apple device of which there will be countless millions of by the end of the years. AND they will be interfaced and will perform consistently app developers will be able to make use of them.

      So yes. It does mean that now Apple did it, it's now important.

    10. Re:haha by iluvcapra · · Score: 3, Funny

      Her brother is the Kwisatz Haderach...

      --
      Don't blame me, I voted for Baltar.
    11. Re:haha by WolfgangPG · · Score: 1

      This has been in some Windows Phone since the Lumia 1020. Apple isn't first ever.

    12. Re:haha by Karlt1 · · Score: 3

      That would be true if Android phones weren't YEARS ahead of Apple phones in terms of technology

      Which technology would that be? Definitely not processor technology.

    13. Re:haha by Anonymous Coward · · Score: 1

      The distortion field is strong in you young padawan.

    14. Re:haha by AaronW · · Score: 1

      My Verizon Galaxy Nexus phone which is almost three years old has barometer support, NFC, etc. Apple is nothing more than re-packaged yesterdays technology.

      --
      This post is encrypted twice with ROT-13. Documenting or attempting to crack this encryption is illegal.
    15. Re:haha by Anonymous Coward · · Score: 0

      Nowhere near as strong as the bullshit-ometer your comment is. Everything the prior poster said is spot on. You guys just prefer to look the other way when "obvious" is staring you right in the face.

  4. I wish I could read by CO_gun_toter · · Score: 5, Funny

    I read the lead in three times, each time reading HeaLthKit as HeathKit. I must be officailly an old fart...

    1. Re:I wish I could read by Mr+Z · · Score: 1

      Ok, so I wasn't the only one.

    2. Re:I wish I could read by Anonymous Coward · · Score: 0

      Wow. Didn't realize it wasn't until I got down here. Having a WTF moment...

      Burr Brown! Burr Brown! Burr Brown!

    3. Re:I wish I could read by Anonymous Coward · · Score: 0

      Ditto here. Even though I never actually built a Heathkit, they were a part of my formative years. Right around the time I might have built my first radio kit, I got a C-64 and the rest is history. The wiki page even cites the introduction of PCs as siphoning off the types of people who would have built kits.

    4. Re:I wish I could read by ColdWetDog · · Score: 3, Insightful

      Presbyopia and Helvetica. A miserable combination.

      Getting old is not for the weak.

      --
      Faster! Faster! Faster would be better!
    5. Re:I wish I could read by Anonymous Coward · · Score: 0

      Apple used to be ruled by moderates. Now they gone full nutcase Faux Knews drones. They hate us now. That is why they are doing this to HeathKit. They are trying to destroy our fond memories. Those people hate good memories. If they can't kill our memories, they'll kill us.

    6. Re:I wish I could read by Guest316 · · Score: 1

      Eyup, caught me as well. I even still have some Heathkit gear kicking around here.

  5. iOS and OSX by koan · · Score: 0

    Now with even less privacy!!!

    --
    "If any question why we died, Tell them because our fathers lied."
    1. Re:iOS and OSX by Anonymous Coward · · Score: 0

      Now with even less privacy!!!

      They can already triangulate you anyway based off cell tower data, along with any number of phone-home apps that you joyfully agreed to the EULA.

      Even I'm not seeing a privacy correlation between barometric pressure and YOU (adjusts tin-foil hat)

    2. Re:iOS and OSX by ColdWetDog · · Score: 4, Funny

      Now with even less privacy!!!

      They can already triangulate you anyway based off cell tower data, along with any number of phone-home apps that you joyfully agreed to the EULA.

      Even I'm not seeing a privacy correlation between barometric pressure and YOU (adjusts tin-foil hat)

      Now they can tell how high you are.

      --
      Faster! Faster! Faster would be better!
  6. Open source? by TheRaven64 · · Score: 1

    If it is open source (and a cursory look around the web site didn't show me any links to the source), it's a shame that it isn't in F-Droid.

    --
    I am TheRaven on Soylent News
  7. I guess Apple was feeling the pressure by Mister+Liberty · · Score: 1

    I know what they're going through. I had my last apple years ago. These days, when I find one, I toss it back over the fence.

  8. wonder who will be the first by zlives · · Score: 1

    to implement the anal probe functionality. I know the idea is rather old at this point. Clearly the populace is not vocally butt-hurt enough just yet about the lack of privacy, or maybe they are and we just need the data about their sphincter tightness... in the cloud aggregate database gathered by the APF module.

    1. Re:wonder who will be the first by Anonymous Coward · · Score: 0

      to implement the anal probe functionality. I know the idea is rather old at this point. Clearly the populace is not vocally butt-hurt enough just yet about the lack of privacy, or maybe they are and we just need the data about their sphincter tightness... in the cloud aggregate database gathered by the APF module.

      Gives a whole new meaning to shitcanning a project.

  9. yay! by Charliemopps · · Score: 1

    Yay! We can finally all figure out what the average weather inside teenagers pockets is! Woot!

  10. Barometers In iPhones! by JohnStock · · Score: 2

    Remember Barometers In iPhones.. that's iPhones.. remember Barometers In iPhones.... Smallprint: oh yeah, Android had them for years

    1. Re:Barometers In iPhones! by StormReaver · · Score: 0

      Smallprint: oh yeah, Android had them for years

      I now expect Apple to launch a billion dollar lawsuit against Samsung over the lowercase letter, "i" in Android. Alternatively, I expect Apple to launch a billion dollar lawsuit against Samsung for showing atmospheric pressure in millibars; thereby infringing upon Apple's invention of the word.

  11. High frequency pressure waves by nadaou · · Score: 4, Interesting

    If you get the chance to monitor the barometer at high frequency there are a couple neat atmospheric phenomena which you can observe.

    The shockwaves which preceed an oncoming strong front or thunderstorm are especially cool to watch.

    --
    ~.~
    I'm a peripheral visionary.
  12. What for? by Ksevio · · Score: 2

    I know my android device has a barometer, but I can't seem to figure out why. Sure it's kind of neat to be able to see the pressure graphed over time, but I don't think it's a big selling point on devices. Is it just a side effect of some other hardware that makes it easy to implement or something?

    1. Re:What for? by Anonymous Coward · · Score: 0

      I have heard it reduces GPS time to first fix (no citation tho)

    2. Re:What for? by Anonymous Coward · · Score: 5, Interesting

      It can help GPS fixes be acquired faster. Barometers provide a rough estimate of altitude and can aid GPS fixes. See https://plus.google.com/+DanMorrill/posts/jVJhPyouWDP

    3. Re:What for? by Nkwe · · Score: 1

      I know my android device has a barometer, but I can't seem to figure out why. Sure it's kind of neat to be able to see the pressure graphed over time, but I don't think it's a big selling point on devices. Is it just a side effect of some other hardware that makes it easy to implement or something?

      Accurate altitude detection? GPS altitude isn't that accurate (at least on cheap consumer level GPS receivers). I have a hand-held Garmin GPS targeted at hiking and it has a barometer built in for more accurate altitude. Perhaps phones are adding them for the same reason.

    4. Re:What for? by ATH500 · · Score: 1

      Because pressure can give information on what altitude you are at which enables GPS to find your position faster and more accurately.

    5. Re:What for? by stephanruby · · Score: 2

      Actually, the barometer on my phone is pretty good. Absent a radical atmospheric change, it roughly knows when I've climbed one floor in an elevator for instance. I doubt that the gyroscope sensors could be giving it this level of information. In any case, by itself this information is almost useless, but when correlated with other data points from other sensors, that's when application developers could use that information to infer much more useful information.

      For instance, with this kind of information, a car navigation app might be able to realize more quickly that you didn't take the on-ramp you were supposed to take. Or it could infer that you made it halfway through a tunnel. Or it could tell you on what floor you've parked your car (assuming, it could calculate out the atmospheric information it could obtain from other sources). Etc. The same goes for health apps. Walking on a flat surface vs. walking uphill makes a world of difference in the number of calories you're burning. I personally very much doubt that the cheap pedometers you can get at the local drugstore for less than 10 dollars can tell the difference between a flat surface and uphill.

    6. Re:What for? by Anonymous Coward · · Score: 0

      Barometers are horribly inaccurate for determining altitude. Occasionally pilots find that out the hard way ;-). What barometers are pretty good at, however, is determining *change* in altitude over a relatively short period of time. Such as going up stairs, or hiking up a hill, etc.

    7. Re:What for? by tlhIngan · · Score: 1

      Because pressure can give information on what altitude you are at which enables GPS to find your position faster and more accurately.

      Provided it's calibrated to the proper atmospheric pressure where you are. Simple weather changes can easily shift your altitude 100 feet either way making it no more reliable than a GPS fix. Granted, if you can obtain the local sea level pressure where you are, you can beat GPS quite handily. But if you can't, you're pretty much guessing your altitude.

    8. Re:What for? by Anonymous Coward · · Score: 0

      Do you even know what you just said? It knows when you go up and down floors. All this data mining, they know your address, your GPS coordinates, and which floor you're on. Maybe not down to the room number, but I bet they can deduce that through other means (steps taken, etc.). One has to wonder what all this information is going to eventually be used for, and perhaps what the use for it is already.

    9. Re:What for? by migloo · · Score: 1

      Barometers are very accurate for determining atmospheric pressure. And if you know the local sea level pressure (e.g. from a weather station) and temperature, you can infer the altitude with better precision than a standard GPS.

    10. Re:What for? by BillX · · Score: 1

      Advertising. Location service can now not only tell what store you're shopping in, but which floor.

      The more user-friendly side-effect is for outdoor activities (tracking runs, hikes, etc.) - much more accurate elevation change info than GPS, whose vertical resolution is terrible.

      --
      Caveat Emptor is not a business model.
    11. Re:What for? by stephanruby · · Score: 1

      Do you even know what you just said? It knows when you go up and down floors. All this data mining, they know your address, your GPS coordinates, and which floor you're on. Maybe not down to the room number, but I bet they can deduce that through other means (steps taken, etc.). One has to wonder what all this information is going to eventually be used for, and perhaps what the use for it is already.

      Yes, I realize what I've said, but I've done the privacy thing. I've rooted my Android phone and installed a privacy-focused ROM, but that just ended up drastically limiting my user experience and annoyed the hell out of me. I'm not doing that again.

      The corporations can overthrow the government and throw you in Gitmo. I'm not going to be the one to stop them. I like my comforts and my conveniences far too much to do anything about it.

  13. Wush ... by angel'o'sphere · · Score: 1

    Every time I feel a small breeze or change in air pressure or a bit of a temperature change I feel also tracked ... somehow is behind me ... I'm sure! I can feel it!
    Or is it just my developing proximity sense?

    --
    Cost free eBook I read (by iBook/Kobo/Amazon/ObookO/Gutenberg etc.): "The Green Odyssey" by Philip Jose Farmer.
  14. What for? by Anonymous Coward · · Score: 0

    It was originally put in to aid in altitude adjustment as the GPS isn't so good at that. A nice side effect is the ability to look at large numbers of pressure readings across populated areas.

  15. drone pilot by thygate · · Score: 1

    so since they have an accelerometer, gyro, compass (orientation), GPS (position), and now even barometer and temperature sensor (reasonably accurate altitude w/ high update rate), all they're missing is a few PWM outputs to directly fly a plane, helicopter, or multirotor as a full-blown auto pilot. I know it's peanuts to interface an MCU with an android phone over UART over USB, but i'm guessing it is also possible on iShizzle, be it over some proprietary interface as opposed to plain old TTL UART. Let's see how long it takes before the first iPhone "drone" kits arrive in the store.

    1. Re:drone pilot by Anonymous Coward · · Score: 1

      $700 phone instead of a much cheaper ArduPilot? Why???

    2. Re:drone pilot by Dynedain · · Score: 1

      They've already been around for years. A few extra sensor provided by the drone kit instead of the iPhone. This just makes them cheaper because your kit doesn't need as many sensors.

      --
      I'm out of my mind right now, but feel free to leave a message.....
    3. Re:drone pilot by thygate · · Score: 1

      oh i agree, but this never stopped anyone. also 3G for telemetry sounds nice, but i guess you could just slap a phone on an ardupilot or any other controller as well.. Also 3DR's APM/pixhawk is way too expensive for what it is imho.

    4. Re:drone pilot by thygate · · Score: 1

      care to share a link/source ? I have never seen any flight controllers that run directly from a phone.

  16. Waiting by Anonymous Coward · · Score: 0

    Welcome to the 21st Century Apple users! (Android users have been here a while.)

    Yes, we know. We're glad we have arrived so we can show the primitives here all the cool stuff you owned and beat against rocks, actually doing things for people (See Also: NFC, BTLE).

  17. Floor In Building by SuperKendall · · Score: 1

    One of the things Apple is using the barometer for is to determine what floor you may be in within a building.

    It could be that with central heating/cooling in most buildings running almost all the time, perhaps a barometric reading could be constant between floors from day to day, even as weather changed...

    Or perhaps just using the change along with accelerometer data to detect shifting between floors.

    --
    "There is more worth loving than we have strength to love." - Brian Jay Stanley
  18. Labs and other pressurized spaces? by seven+of+five · · Score: 1

    Our lab rooms have negative internal pressure with respect to the halls on account of fume hoods, etc. Wonder if a phone barometer gets confused by that?

  19. Big Problem by Anonymous Coward · · Score: 0

    A big problem here is that many office buildings are pressurized above atmospheric. People taking their phones in and out of the building should make for interesting weather forecasts as the "observed" pressure abruptly rises and falls.

  20. secondary microphone by danlip · · Score: 1

    I wonder how long it will take someone to turn this into a secondary (and insecure) microphone. It's already been done with Android's gyroscope.

    1. Re:secondary microphone by Anonymous Coward · · Score: 0

      You'd have to sample the barometer at least 160x per second to pick up the fundamental tone in the deepest human male voices (differenct sources quote values between 80 and 85 Hz).

      It shouldn't be necessary to measure barometric pressure more than once per second, so I wouldn't be surprised if the devices are rate-limited to 1x per second == 0.5Hz audio after Nyquist.

    2. Re:secondary microphone by Anonymous Coward · · Score: 0

      It might be possible to sample 1kHz audio with a few thousand devices sampling at 1Hz in a very controlled settting.

      First assume a uniform distribution of those samples within a given 1 second interval.
      Next assume there's a common source (e.g. public address system).
      Then assume all the sensors are in "relatively fixed" locations, so that their phase relative to the source doesn't change by more than about pi/8 radians anywhere in the target frequency range.

      * Common source plays a deep 0.45 Hz sine wave (not possible with traditional P/A speakers, but it may be possible to produce the effect by playing pure tones separated by 0.9 Hz from two separate loudspeakers; the resulting beat frequency will contain a (f1-f2)/2 Hz component that should be measurable by devices sampling barometric pressure 1x per second).
      * Central server correlates all of the inputs to get proper phase alignment, and it also has to compensate for varying intensity (factors include distance from source and acoustic reflections).
      * Phase-delayed inputs are then plotted into a buffer and averaged for multiple samples in the same bin.
      * Apply a suitable smoothing filter (possibly cosine interpolation) and re-sample at the desired higher frequency.

      If you had access to the data from multiple cell towers, you might have precise enough information to compute the delay and intensity factors for an arbitrary fixed location without having to correlate to a known source.

      In either case, the resulting transfer function would be highly focused on the source location, and you'd probably just hear "noise" for anything far enough from the calibrated source location.

  21. HealthKit vs HeathKit by Anonymous Coward · · Score: 0

    Am I the only one who drops the "l" from HealthKit and reads it as HeathKit? Yes, I know I'm showing my age. Now get off my lawn!

  22. Missing sensors by mysidia · · Score: 1

    Now that they have a barometer... just need to add air motion sensors, a humidity sensor, a thermometer, vibration sensor, UV sensor, and an air quality sensor / airborn particles measurement, Oh yeah, and an Ebola/Microbe detector

  23. Useful for barometric migraines by __roo · · Score: 1

    I know several people who get barometric migraines, or migraine headaches that are triggered when the pressure changes suddenly (usually when it drops). Some of them have told me that migraine medications like rizatriptan and sumatriptan can be effective, but often come with unpleasant side-effects like a racing pulse or grogginess.

    This leads to a dilemma: do you take the medication and deal with the side effects, or do you try to ride out the headache? It's especially frustrating for people who get headaches that aren't always migraines, because the migraine medication doesn't necessarily work on a normal, non-migraine headache.

    This is where a personal barometric pressure monitor that's been with you for the last few hours can be very helpful. If you are trying to decide whether or not to take migraine medication, you can consult your phone and see if you personally experienced a large pressure drop prior to the onset of the migraine. If so, that helps with the decision of whether or not to take the medicine.