How to calculate speed without requiring GPS? I have heard of something called "sensor technology" but am not sure what that means. I am asking because I want to make an app, but I don't think it is battery efficient to use GPS, plus it is for a long-term project so I want the app to continuously run without having to manually turn it on or turn on GPS.
GPS is by far the most accurate way to do this.
You can get access to the accelerometers, but they are not remotely accurate enough for this type of application.
The only other way I can think of would be to get one of those bluetooth adapters that you plug into your car's diagnostic port, and get the speedometer input from there. Then, you're wasting power on bluetooth as well.
Just buy a power adapter for your phone to run on the vehicle.
I tried to measure the speed using Android's accelerometer sensor for an indoor-navigation project but that failed miserably. I intented to derive the current speed from the acceleration/deceleration over time and so in the end calculate movements along the X, Y and Z-axis, but that didn't work out at all. The accelerometer sensors of common Android devices are way too inaccurate for that kind of usage.
So, you will have to use GPS. To reduce battery drain, you can increase the intervals (time and/or distance) in which the LocationManager notifies your App. See the minTime and minDistance parameters of it's requestLocationUpdates() method.
Android allows you to use cellular phone antennas and wi-fi access point antennas as reference points to determine your current location without using the GPS (see: locationManager.NETWORK_PROVIDER).
Once determined your position in two different moments/points you can easily calculate your speed in your code.
I don't think one can calculate speed without the assistance of GPS. Speed depends on distance and time. I am not sure if we can calculate distance just like that.
Anyway look at http://developer.android.com/reference/android/hardware/Sensor.html
There we have different sensor types. Perhaps you can make use of one of those.
I think what you are referring to would be considered "dead reckoning" (http://en.wikipedia.org/wiki/Dead_reckoning) and is possible, but will lead to drift and incorrect speed information, especially if the user of your app doesn't have the device mounted securely to whatever is moving.
Would it be a valid use case for your app to go to sleep and turn off the GPS? You might be able to devise a way to turn the GPS back on when you bring the app out of suspension. If you need the location always, then GPS is your best bet. People understand that GPS based apps require power and will come up with a way to plug it in to use it long term.
Perhaps you should think about the use cases for your app and ask if people are willing to drain their battery power for whatever functionality you will offer.
Using acceleration and time you can calculate change in velocity but you don't necessarily know the starting velocity. Plus the accelerometer in an iPhone probably isn't accurate enough for this anyway, but it's not a bad shout.
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i'm looking for the best way to implement a road navigator that gets the velocity, distance between 2 points using the smartphones techniques.
through my searches i found 2 different tech. using either the accelerometer or android API (android.Location).
some opinions said that using accelerometer wont give me an accurate results because there will be so much noises as a bumpy roads, buildings...etc and calculations will be so complex.
on the other hand using the Android API (android.Location) means i should always be connected to the GPS, doesn't that affect on the battery?!! and as i found i can't open the GPS by myself i used always ask the user for a permission(so boring). and is there an limitation
So kindly help to take a decision, is it useful to be connected 24 hours on GPS in order to update the device location.. or to use the accelerometer??
You definitely should use GPS. The battery will be strained but you get much more accurate result. Sensor should be used only when GPS is not available and for a short distance.
Using GPS you can call location.hasSpeed() and if positive call location.getSpeed() together with getBearing() will give you the velocity.
I am trying to get the user's speed from their Android device, but which is the most reliable way to do it?
There is the location.getSpeed() function that uses GPS; is this a reliable way to obtain the speed? Should I instead calculate speed manually using GPS coordinates obtained? Or is there another way that I'm missing to accomplish this?
IMO, best current approach on Android is to use Location.getSpeed() along with the Google Services Location API and the fused location provider. Then, reality-check this value against Google Play Services Activity Recognition.
The fused location provider integrates some other on-board sensors to tweak location data, which is better than GPS alone. Then, check the ActivityRecognition.getMostProbableActivity() method. If the DetectedActivity is type STILL, your true speed is probably equal to 0. If its ON_FOOT, it's probably a low speed (e.g., 1 m/s). If its ON_BICYCLE or IN_VEHICLE, you're probably fine relying on the speed output obtained directly from Location.getSpeed(). You'll also want to check the DetectedActivity.getConfidence() value too, and set your own threshold for a confidence level you feed "confident" with :) when relying on these values.
I'd also definitely suggest that you do NOT simply average sequential positions to get an average speed between two position (if you do this, it needs to be an average over a large number of positions). In my benchmarking on mobile devices (see my dissertation here, pages 105-106, and 137-138 especially), I've found instantaneous speed calculated by the GPS subsystem (which is typically based off of the Doppler shift of GPS carrier signals) to be far more accurate than the positions derived from GPS. 95th percentile of speed observed while stationary indoors (using assisted GPS only, no sensor fusion) was 1 m/s on a Sanyo Pro 200 I tested. I was able to filter out a significant number of position outliers using speed data (see page 137-138) in some intelligent energy management techniques I was evaluating. With sensor fusion, and activity recognition to help filter outliers, accuracy should be better than this on a similar device.
Finally, and I can't emphasis this enough, do you own testing on real devices, as many as you can get a hold off, and preferably the most popular models out there. Android has a variety of OEMs putting out devices, which will all have their eccentricities. Your best bet it to create a solution that targets the most popular models, acknowledging that it's unrealistic to get a solution working perfectly on all models.
It seems that the getSpeed() method is not always reliable, especially at low speed and when gps coverage is not optimal.
You can have a look at this question and this one which are both about alternatives for getSpeed().
The android developper page however says that you'll get better performance by using the Google Location API.
So it appears that the choice is depending on the usage of your app: if you target slow displacement in area with poor gps coverage (walking in the wood), use your own implementation. Fast in area with good GPS coverage, use the Google Location API.
The best way for devices that are moving faster than walking speed, is to use directly the location.getSpeed().
For pedestrian, or other slow speed situations, this is not quite easy, maybe it is simply impossible to have a valid slow speed that is valid at the moment.
Some try to evaluate the history and do an averaging, or threshold based approach, this will improve for a specific application / usage.
But the simplest is to design your App to ignore low speeds.
Some links related to speed:
GPS position correction
Smooth GPS data
What is the best way to detect user device moving? For now I'm using network/GPS location determining best coordinates on small interval. But it would be great to improve accuracy user movement information up to meters. Geolocation strongly depends on network connection quality or weather.. Is there a way to find very accurate info about device moving? May be accelerometer can help?
Accelerometers tend to be a poor way to measure distance moved, as the slightest error in the measurement of acceleration or orientation rapidly integrates to a substantial position error. That's even more true with low-accuracy components used in a consumer device - inertial navigation systems used in aircraft/spacecraft are not cheap, and even those might not be accurate enough for your needs.
If you want positioning accuracy, especially over any duration of time, you need to measure in relation to the outside world, as GPS does. There are various beacon systems available using things like ultrasonics, or even adding pretend satellites to the GPS system which you could look into, but it's not going to be simple.
I am trying to implement a fitness app that can keep track of the running speed and running distance in Android.
It looks like I can either use GPS or Accelerometer to calculate these information.
Since a runner may put his phone in hand, on the shoulder or in his pocket, my first intuition is to use GPS to get locations and calculate running speed and running distance. But recently someone telled me that I can also use Accelerometer also does that.
My question is: In Android, which approach is better to calculate running speed and running distance, GPS or Accelerometer?
I suspect that pedometers are based on accelerometers because accelerometers are cheaper than GPS to use. in fact I think a lot of pedometers don't even try to measure distance. just acceleration jolts which equal steps. and then if they give you a distance measurement, it's by multiplying detected steps by a guessed or average step size.
GPS (if you are in an area where it works!) will do a very good measurement of distance. Even with a very cheap GPS receiver. All being basically OK, you should expect start and end positions to within 10m, and so for a 1km travel, you have 20m of uncertianty, which is 2% total distance uncertianty. This uncertianty goes down linearly with distance travelled (ie a 2km run will have 1% uncertianty, 4 km run will have 0.5% uncertianty, etc) the issues here will be with your realtime displays (GPS position jumps from satellite switching giving massive speed values, or immediate loss of signal giving a loss of all immediately displayable data)
I think that with a good accelerometer, starting from stopped you can continually integrate the signal to get speed, and continually integrate that result to get distance... I am just unsure what kind of accelerometer quality you get in any given phone? you may need to filter for noise or even garbage data.. And you also need to consider what accuracy it has. 20% accuracy in your sensor would make for a very bad distance tracker. So you might have to work with step counting and step size guesstimates.
perhaps a combination of both could work?
I'd be tempted to use the accelerometer data (either integrating or step counting depending on what will always work) to track speed and distance in short timeframe, then with much longer timeframe, generalised GPS data could be used to correct or scale that data from the accelerometer. Especially if you filtered/blocked GPS data based on uncertianty measurement at any given time.
Adding to what Julian said ... Normally GPS doesn't work under the roofs therefore for indoor gyms it will not work. Theoretically GPS signals are not bothered by clouds but when I was working on my GPS application, I had experience of unavailability of GPS signals in really bad weather (this might not be your case as no one will go on jogging in thunder storm :D)
Agreeing with Julian, you should use both GPS and accelerometer to build a reliable app for every condition.
The best results are obtained by using both of them, through sensor fusion. See:
Android accelerometer accuracy (Inertial navigation)
You will have accuracy problems if you just use either the GPS or a pedometer algorithm.
All pedometers I know are based on accelerometers. I guess, GPS is not precise enough for this stuff. It may say "no motion" while you did some steps, it's also dependent on the area you are trying to use it.
I'm new in Android and I would like to ask you is there any possible way to know if the Android phone moved about 5 meters from its current location ?
One idea is to use the accelerometer to detect when the phone is moving. Naturally, you can't estimate the distance moved very accurately, but it might work for your application. If the accelerometer says the phone is moving for more than 5 seconds or so (maybe you can detect a pattern of movement?) you might infer that the phone moved significantly from its original position.
Of course, the user can trick your app by shaking the phone...
A good resource concerning GPS can be found at the official site: http://www.gps.gov/systems/gps/performance/accuracy/
The short answer, however, is that the GPS accuracy of a specific phone at a given moment is dependent upon several variables. Those that are most pertinent to your question would be the actual hardware of the device, and the environmental conditions at present. Typically, a phone under good conditions can expect at best 10m of lateral accuracy. Taking into account poor conditions, local interference, limited satellite connectivity, etc, can push the error of a reading much higher. Unfortunately, consistently and precisely measuring a movement of 5m is unlikely.