My app will have one UILabel that displays the current speed of the iPhone. And of course if iPhone is falling down, the falling speed will update to that label aslo. For short distances, I believe GPS cannot do this, and the accelerometer is also not suitable.
Is this task possible? If so, how to implement it?
No, GPS can not do this. (not one in the IPhone). But it is possible with accelerometer ( but do not await high precision )
Related
Is there a way to hook into/run a bg task in an iOS app depending on accelerometer action? I.e. the unit elevates three feet, or goes in a certain direction
No, there's not. You would have to run your app constantly in the background, monitoring the accelerometer constantly. And note that you really can't detect things like "raises 3 feet". The accelerometer is pretty bad at measuring changes in position because it is very subject to drift. What it detects is acceleration, so it detects jerks, bumps, and thrust. If it's moving smoothly in a car at 100 KPH it can't tell, for example.
I developed an app which calculates distances between current position(lat and long) and another stores location. Current position comes from built-in Gps on iPhone. In some buildings is working indoor( like 8meters far from windows or doors). Why is it working indoor? How can I still get GPS signal without WiFi/3G/4G connection?
i hope someone can answer me
Welcome to SO.
The short answer is, it's out of your control. GPS is not reliable indoors. Sometimes you are able to get a signal, sometimes not. Metal frame buildings are worse than wood-frame buildings, and brick also tends to interfere with GPS signals. Florescent lights also tend to interfere.
In a given indoor setting you'll either get a GPS signal or not.
I'm trying to detect if my iPhone has been thrown into the air.I've tried using core motion's acceleration API and its altitude API.However, because the axes are fixed to the phone doing the detection of the changes is incredibly difficult.Is there a better way to do what I want?Is it possible to speed up the refresh rate of the CMAltitude API?
In freefall, you should see your 3 accelerometer values go to 0. Even in a projectile type of fall (throwing), the phone is in freefall as soon as it leaves the thrower's hand.
This white paper talks about using a MCU, but the concept is there.
http://www.nxp.com/files/sensors/doc/app_note/AN3151.pdF
Is it possible to calculate small distances with CoreMotion?
For example a user moves his iOS device up or down, left and right and facing the device in front of him (landscape).
EDIT
Link as promised...
https://www.youtube.com/watch?v=C7JQ7Rpwn2k position stuff starts at about 23 minutes in.
His summary...
The best thing to do is to try and not use position in your app.
There is a video that I will find to show you. But short answer... No. The margin for error is too great and the integration that you have to do (twice) just amplifies this error.
At best you will end up with the device telling you it is slowly moving in one direction all the time.
At worst it could think it's hurtling around the planet.
2020 Update
So, iOS has added the measure app that does what the OP wanted. And uses a combination of accelerometer and gyroscope and magnetometer in the phone along with ARKit to get the external reference that I was talking about in this answer.
Iām not 100% certain but if you wanted to do something like the OP was asking you should be able to dig into ARKit and find some apis in there that do what you want.
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Can I detect the force or pressure exerted by a user (musician's) finger?
Not yet.
There's a technical demo showing how to do it. See http://tenonedesign.com/blog/pressure-sensitive-drawing-on-ipad/ . Hopefully something comes out of that. :)
Yes you can detect finger area, which is similar. Really! You just don't get point-pressure which requires a different sensor technology.
You can get a number that's the major radius of your finger in millimeters from every finger individually. It's essentially a processed number related to the number of pixels you are covering with the finger. Unfortunately, I haven't been able to get a straight answer on whether this is a problem to ship this way, so I have to ship with it disabled. But it works. It returns a value from 7.0 to about 11.0, it varies wildly, and you might want to low-pass filter changes to this value.
float vf = 10.0;
id valFloat = [thisTouch valueForKey:"pathMajorRadius"];
if(valFloat != nil)
{
vf = [valFloat floatValue];
}
As an iPad developer, it drives me COMPLETELY insane that this has worked since the iPad shipped, works now in iOS4.2, and still doesn't appear to be sanctioned. This feature is a basic requirement for many classes of application if you want something that's more than a $2 toy.
You cannot detect pressure but you can detect velocity of movement (distance/time) and you could establish a linear relationship between velocity and force -> volume. You could make a bell ring louder, for example, by swiping your finger vigorously, rapidly across the bell, and quietly by a gentle, short, slow stroke. Probably would work OK with harp strings.
Done. See my answer in Tap pressure strength detection using accelerometer