I've been developing an app for a project of mine which includes a module where I track the steps of the user using an accelerometer.
As of now, I currently can only track the number of steps that the user walks but not the speed. I did some research but I couldn't find much.
The code that I'm using for the pedometer module in the app is from this:
https://github.com/google/simple-pedometer
Any help would be appreciated.
Accelerometer with gyroscope won't work here because of dead reckoning - drastically increasing error caused by integrating original error. You should calculate speed by taking GPS coordinates, taken with some equal time intervals. I used that here: https://github.com/AlexShutov/LEDLights/tree/ReadingSensors/app/src/main/java/alex_shutov/com/ledlights/sensor/gps
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I've been doing a bit of research on a problem we are trying to solve. I think this is the best approach but please add in your opinions
We are trying to calculate reaction times in a real world driving scenario and would like to use a mobile phone as the data collection device. What we are trying to accomplish is how much acceleration and more importantly deceleration a driver exerts when exposed to certain prompts.
I found this paper that has allot of useful information Accelerometer physics
The problem is that we most likely will not have a calibration time to start at zero.. however it is assumed that the driver is starting at 0. We will use GPS positioning to locate the vehicle, tracking the time stamped location data we should calculate the time when the prompt took place then using the time stamped accelerometer data we should be able to calculate their reaction to the prompt.
This is the best way I have found to solve the problem however I'm not sure if the accelerometer data will be rendered useless because of not being able to calibrate it and also the noise seen from vibrations may be too great to use the data... Has anyone tried or used these types of methods before?
Interesting application.
You are missing an important point. You either have to implement the so-called sensor fusion yourself or use the sensor fusion provided on the platform you are using. Both Android and iPhone have one.
The TYPE_LINEAR_ACCELERATION (Android, SensorManager) or userAcceleration (iPhone) should be sufficient for you.
As for the linked PDF, don't try integrating the acceleration, you will get very poor results. Even though that answer is about position, the velocity will already be inaccurate. I would try the GPS instead.
I know it's very old question but since I am recently working on a similar project let me share what we did in our company. We simply used OBD-II dongle to get velocity of car. There are many API's that return information about vehicle.
PID010D returns speed of vehicle. I'm using this PID to calculate distance between points A and B since there is no PID to return Odometer :(
There are few libraries on github that you can find easily by search. This mine. This is not library but after run on your device you can see how it works.
I am biggener in android. I am trying to implement a fitness app that can keep track of the running speed and running distance in Android. How can i calculate the above mentioned things ?
In theory you could analyse windows of accelerometer data and count the number of peaks and the forces of those to determine running. Then, if the user has entered an average step distance, that could give an equation of distance.
Would be a lot easier using GPS as it provides the speed directly.
You might be interested in this library: https://github.com/mcharmas/Android-ReactiveLocation I recently added Activity Recognition, which can tell you whenever a user starts running. Might take a little while from one begins to run before the phone 'knows' that as being the activity, though.
I'm trying to write an android code that uses the device sensors to detect freefall scenario.
I searched the web a lot for a solution to this problem but I was unable to find anything useful.
I did see that there are several apps that does exactly this so it is possible, but i didn't find any code sample or tutorial on how to do that.
Can anyone please help me with a code snippet or even with a mathematical calculation using the sensors data?
Thanks in advance
The device is in free fall if the length of the vector given by TYPE_ACCELEROMETER is approximately zero. In theory, it should be exactly zero, in practice, it well be only near zero. So you need to come up with some threshold by trial and error and declare that the device is in free fall if the length of that vector is below this threshold.
Check out the API here SensorEvent Values and the math behind FreeFall here Wikipedia.
You are trying to detect speed in some direction. Look at the motion equations on wikipedia. You are detecting acceleration over time that is normalized for the gyroscopic rotation of the device.
Also see: How to approach Fall Detection Algorithm
From what I've read, the accelerometer normally measures gravity. Thus, if you're in freefall and the device is not being moved laterally, all accelerometer readings should be zero. (Disclaimer: I have not written any accelerometer code.)
Google the iFall project by a group at Florida State University. The have published a paper describiing the approach they took for their Android iFall application, which gives a host of references for further/extended study. They also have an API available and explain how to use it, if you want a fast shortcut approach. (To use their API, I believe you just need to download and install their iFall app form the Playstore)
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Possible Duplicate:
How to Count the Number of Steps Using the Accelerometer
Are there any well known algorithms to count steps based on the accelerometer?
Hi i have developed android application. In one module I have to create a pedometer. Now at this stage I have to count the steps user walked by using accelormeter. I have search on internet and found different methods but none of that working. I have tried this
Does anyone have an idea how to achieve my goal? Any help is appreciated.
The simplest solution would be to have a time-window and a number of thresholds. The signal gets a form of a double wave, and you can split a step into several parts. You may need to have several windows and corresponding threshold values to recognise one step. But keep in mind that this signal will change if someone is walking upstairs/downstairs or running or just walking with different pace. You will get great variability if you actually going to try it with several participants.
Threshold values will differ greatly between devices. Frequency of measurements will also have an impact. Standard frequency that allows one to detect walking with normal pace is about 10Hz, some devices use 20Hz, if you go over this you will get lots of data and little information. Manufacturers do use different versions of accelerometers, so if your software works on one phone, there is no guarantee it will work on the other device even of the same model.
I would start from plotting your signal first. Also don't forget that the phone can be in different positions in a pocket (unless you fix it somehow) so the threshold values will float. All clinical pedometers are usually affixed to the leg in a certain position.
Consider using mono-axial accelerometry instead of 3-axial, the signal analysis gets much more easier to begin with. Also take a look at the Fourier transformations and wavelet analyses.
See the image below to get a basic idea of how walking looks with a 3-axial accelerometer. I made it when was doing similar task (walking is the noisy bit).
And this is how walking looks with a mono-axial accelerometer (again noisy bits)
This seems to be pretty reasonable and accurate:
Enhancing the Performance of Pedometers Using a Single Accelerometer
Anyhow, I am also interested in finding a good algorithm.
I've been doing a bit of research on a problem we are trying to solve. I think this is the best approach but please add in your opinions
We are trying to calculate reaction times in a real world driving scenario and would like to use a mobile phone as the data collection device. What we are trying to accomplish is how much acceleration and more importantly deceleration a driver exerts when exposed to certain prompts.
I found this paper that has allot of useful information Accelerometer physics
The problem is that we most likely will not have a calibration time to start at zero.. however it is assumed that the driver is starting at 0. We will use GPS positioning to locate the vehicle, tracking the time stamped location data we should calculate the time when the prompt took place then using the time stamped accelerometer data we should be able to calculate their reaction to the prompt.
This is the best way I have found to solve the problem however I'm not sure if the accelerometer data will be rendered useless because of not being able to calibrate it and also the noise seen from vibrations may be too great to use the data... Has anyone tried or used these types of methods before?
Interesting application.
You are missing an important point. You either have to implement the so-called sensor fusion yourself or use the sensor fusion provided on the platform you are using. Both Android and iPhone have one.
The TYPE_LINEAR_ACCELERATION (Android, SensorManager) or userAcceleration (iPhone) should be sufficient for you.
As for the linked PDF, don't try integrating the acceleration, you will get very poor results. Even though that answer is about position, the velocity will already be inaccurate. I would try the GPS instead.
I know it's very old question but since I am recently working on a similar project let me share what we did in our company. We simply used OBD-II dongle to get velocity of car. There are many API's that return information about vehicle.
PID010D returns speed of vehicle. I'm using this PID to calculate distance between points A and B since there is no PID to return Odometer :(
There are few libraries on github that you can find easily by search. This mine. This is not library but after run on your device you can see how it works.