Can the iphone detect its movement in terms of distance?
Would one be able to use a built in function on an iphone to determine the distance the phone has moved so that the speed of movement can be calculated?
Basically my question is
can an iphone detect its position and distance moved without using the gps?
thanks
You probably could with some clever math.
Basically, integrate over the accelerometer data.
For all the details, see http://www.freescale.com/files/sensors/doc/app_note/AN3397.pdf
No, the only sensor that the device has that can calculate "distance" is via the Location API, which will make use of the GPS. Accelerometer and gyros (in iPhone 4) can give precise measurements of changes in orientation, but not distance travelled.
Not easily, there are a couple of ways you can do this but they have severe limitations and you'll have to write all the code yourself.
One way is to use the accelerometer and try and calculate the distance from the forces on the phone, this is never going to be very reliable.
Another way is to use wifi, essentially looking at the signal strength to determine distance from the router (I think this is only possible using private APIs and requires several routers to be at all accurate). Or listen from a router to find out how far away the iPhone is.
Related
I want to create an iPhone application that executes certain actions based on what direction you tilt your device. For instance if you tilt the device so your phone screen is pointing towards the floor execute action x, if you tilt your phone so the phone screen is pointing towards the sky execute action y. I found some examples using the iPhones accelerometer in order to detect the tilt of the phone, but the values the accelerometer generated were so sporadic it was hard to execute a certain action based on specific values.
I'm relatively new to using the accelerometer within applications so I might be going about this completely the wrong way, any help would be appreciated.
The raw data out of the accelerometer is pretty jittery. You'll want to apply a high pass filer or a low pass filter at a minimum to the raw data. See the Apple sample code AccelerometerFilter.m for some basics on how to use it. I found that that wasn't sufficient and I keep a time-moving average of the data to accomplish what I need. You'll certainly need to play around with this to get it to do what you want it to do.
I have a GPS app that I would like to detect if the user is standing still and not moving. Using Core Location works for this, but is sometimes not accurate because new updates move and gives the illusion of speed and motion.
So, I am wondering if in addition to that, I can also use Core Motion. Is this a good idea to detect motion such as someone walking, running, driving, etc, and know when they are no longer doing that motion? Or, is Core Motion only for small movements such as tilting the device or lifting it to your ear?
I wanted to tell others who visit this question what I've learned and what I think about this approach.
I have been doing some research of my own to know whether this is possible, and more importantly, even if it is what is the battery consumption and accuracy of the location change detected. For Android though, this question was asked quite sometime back. The answer provides links to this Google Tech Talk. At 23:20, the speaker talks about how difficult it is to achieve this and the accuracy you will achieve in the results.
Even though I have to come to realize the battery consumption from sensors on the iPhone is a little lesser than in most Android phones, I still think this is a costly affair in terms of accuracy and battery consumption.
you can use the GPS with the sensor readings to distinguish between walking, running, etc. if you combine the tilt angle frequency change and the GPS speed information (you need to do some work to get some of this info of course, but thats the way to do it).
You are talking about 4 different measurements from 4 different sensors (technically more than 4 but..) -
Latitude & Longitude - from CoreLocation. It uses a mix of GPS + cell tower triangulation.
Accelerometer - the current orientation of the device in 3D space.
Gyroscope - orientation of the device on its own axis.
Magnetometer - which tells you which direction a device is point w.r.t south,north,east,west
Of all these I think only Latitude & Longitude are of use to you. Basically what you do is to make the sensitivity (i.e. the update rate from the sensor) a bit more relaxed. With some tweaking around with this you should be able to tell with good accuracy if a person is standing or moving.
I'm wanting to figure out if a user is not moving at all, walking, or running using the iPhone. I'm not trying to implement a pedometer. I just want to know around about if someone is moving briskly, slowly, or not at all. I don't need mph or anything like that.
I think the accelerometer may be able to do this for me, but I was wondering if someone knows of any tutorials or example code that might be able to point me in the right direction?
Thanks to all that reply
The accelerometer won't do you any good here - it will only capture changes in velocity.
Just track the current location periodically and calculate the speed.
There are no hard thresholds for walking vs. running motion, so you will have to experiment a bit. The AccelerometerGraph sample code should get you started on how to get and interpret accelerometer data.
The Accelerometer is good, but if the user has an iPhone 4 or iPad 2 you should use the gyroscope.
CMMotionManager and Event Handeling Guide - Motion Events
Apple Documentation is the best example you can get!
People have a different bounce in their step between walking and running which can be measured with the accelerometer, but this differs between individuals (what shoes they are wearing, what surface they are upon, what part of the body is attached to the iPhone etc.), and this motion can probably be imitated by shaking the iPhone just right while standing still.
Experiment by recording the two types of acceleration profiles, and then use some sort of pattern matching to pick the most likely profile candidate from the current recorded acceleration data.
I have been doing a bit of research, but I cannot seem to find a way to determine small distances (centimeters and meters) using the sensors in Android or iOS devices.
Bluetooth appears too inaccurate and require more than one device, GPS only works over larger variations in distance, and small variations in rotation seem to make using the accelerometer nearly impossible.
Is there a method that I am unaware of that would allow me to do such a thing? I am familiar with Calculus, so using Integrals to determine distance based on changes in time and velocity/ acceleration is not a problem for me, I just do not know how to determine those things.
Thank you.
There's no sensor in these devices which is able to give you the desired accuracy without exterior help.
If your use case allows for a bit of external setup, here are some ideas:
You could use the camera and computer vision to calculate device movement. You could, for example, use ARToolkit to measure the distance to a visual tag fixed to a wall. In close distances you can get pretty high accuracy (mm) using this technique.
Another idea would be to measure the distance to a solid object, like a wall, by emitting a short audio signal using the speaker and measure the time until the echo arrives at the microphone. This would be more of a research project, though.
You CAN use the accelerometer to measure distance travelled
(if ONLY absolute displacement is involved).
Have the user hold the device flat and walk from pointA to pointB.
The user presses a "Start" button in ur app as he starts from A and
presses an "End" button in ur app as he reaches B.
Calculate the double-intergral of AccelX & AccelY seperately over time
between the 2 button presses. These will be distX & distY respectively.
Total displacement will be sqrt( (distXsquared) + (distY squared) ).
GoodLUCK!!
Regards
CVS#2600Hertz
Just as a thought experiment, you should be able to do this using a combination of the accelerometer and the compass on each device.
However, whether the accuracy of these sensors is enough for what you want to do...well I think you'd just have to try it.
I'm working on locating an iPhone device in 3D space.
I can use lat/long to detect physical location, I can use the magnetometer to figure out the direction they're facing, and I might be able to use the accelerometer to figure out how their device is oriented, but I can't figure out a way to get height of the device off the floor.
Specifically, I need to know if the user is squatting down, or raising their hand toward the ceiling (a different of about 2 meters/6 feet).
I posted a more detailed description of what I'm trying to do on my blog: http://pushplay.net/blog_detail.php?id=36
I would love any suggestions as to how to even fake this sort of info. I really want the sort of interactivity and movement that would require ducking and bobbing, versus just letting someone sit back and angle the phone -- kind of the way people can "cheat" playing with a Wii...
The closest I could see you getting to what you're looking for is using the accelerometer/magnetometer as an inertial tracker. You'd have to calibrate the user's initial position on startup to a "base" position, then continuously sample the sensors on a background thread to build a movement model. This post talks about boosting the default sample rate of the accelerometer functions so that you can get a pretty fine-grained picture of the user's movements.
I'm not sure this will solve your concern about people simply angling the device to produce the desired action, but you will have to strike a balance between being too strict in interpreting movements and allowing for differences in movement
The CoreLocation stuff gives you elevation aswell as lat/long, so you could potentially use that although there are some significant problems with this:
Won't work well indoors (not a problem for Sat Nav, is a problem for games)
Your users would have to "calibrate" (probably by placing the phone on the floor) each location they use!
In fact, you'd need to start keeping a list of "previously calibrated locations"... which could vary hugely just in one house (eg multiple rooms and floors). Could get in the way of the game.
Can't be used on moving transport (tranes, planes, automobiles... even walking) because elevation changing so frequently.
Therefore I'd have thought that using the accelerometer as a proxy for height is a substantially more preferable route than determining absolute elevation.
I am not intimately familiar with the iphone. But it might require a hardware add-on. (which you probably don't want to do). After thinking on this the only way I know how is through light or more specific laser. You shoot out a laser on the floor and record the time it takes to get back. It's actually not a lot to put this hardware together and I am sure the iphone has connections for peripherals. Unless osmeone can trump me, I say ther eis no way to do that with an image.