Viewing a single comment thread. View all comments

other_usernames_gone t1_irt1erh wrote

Maybe check the direction of the acceleration.

If you drop a phone and don't crash you'll get 9.8m/s^2 down for half a meter to a meter and then a stop.

If you crash you'll also get quite a lot of lateral declaration as you hit a tree or whatever and brake hard. The initial breaking will probably be longer than the amount of time a phone takes to drop.


celaconacr t1_irti6tt wrote

I don't think you could detect the force direction quickly enough to do that.

On a static phone you can detect down using gravity. When the phone is potentially spinning and moving in any direction you can't as easily separate the forces applied from the phone motion. Essentially you get an output of forces in 3d but it isn't tied to a direction directly.


NotAHost t1_iruc8va wrote

You have an IMU that uses both a gyroscope and acceleration.


designingtheweb t1_iru80s0 wrote

You can drop the phone upside down, back first, screen first, etc. Any orientation is possible. It can even be spinning. I will be hard to detect down.


guiltycornet77 t1_irw4q4t wrote

You don’t need the direction however, just the magnitude of the acceleration in 3D prior to impact. If it is within the ballpark of 9.8 m/s prior to the massive impulse spike caused by it hitting the ground you can disregard the spike as a drop. If the phone is at a resting state/a state with very little acceleration prior to impact (ie a phone on a dash in a car that immediately hits a wall) or has a large magnitude of deceleration (driver hits the breaks quickly before impact) than you can diagnose that as a crash. You don’t need direction of acceleration if you just simplify the problem


kreiger-69 t1_irvfz7x wrote

Impact.....if after twenty seconds everything remains stopped then call.....if gps continues to move then don't ring 999


RC1000ZERO t1_irvop3o wrote

smoke detectors do something similiar(at least Photoelectric smoke alarms do) when they first detect smoke(by the lightbeam being interupted/scatterd and thus the current changing on the sensor) they send out a couple more light flashes in quick sucession(they usualy send a beam every so often(i think it was every second or 5 seconds? anyway, not constantly)to check if the disturbance was just a dust particle or actual smoke THEN it rings the alarm....


not hard to implement something similiar into this i imagine.


crappy80srobot t1_irvd4eq wrote

My pixel has gone off twice over the years. The first time I slammed my phone down in the seat because I was mad at someone. I didn't know what the alarm and the person talking was at first because I forgot I had the feature. Kinda put me in a panic. Good thing it ask if your okay first and doesn't immediately call 911. It really seems like a non-issue as long as the iPhone functions the same way. Honestly don't know why this is a story or why anyone talks about this feature. It's nothing new and these instances have been seen before. I feel like I heard the same talking points three years ago.