I am developing an Android application that requires devices to be laid side by side and/or above and below each other.
I know I can use the Nearby API to detect devices "Nearby" however I need something a little more "Finer Grained".
My app needs to be able to identify a device laying either on the left side, above, right side or below. While all devices are laying flat on a table (for instance).
I can find nothing on the web that describes this use case.
Is it possible?
UPDATE
My use case is that I want Android devices to be able to detect any number of "Other Devices" laying either to their left or right. The devices will be laid out horizontally with a "small" gap between each one.
In the same way that you might layout children's lettered blocks to spell out a word or phrase, or numbered blocks to make a sum.
not only should the line of devices be able to detect their immediate neighbours to their left and right the two devices at either end should be able to detect they they are the start and end (reading left to right) of the line.
Using proximity sensors is a likely way to solve your question. TYPE_PROXIMITY will gives the distance from a near by object. TYPE_MAGNETIC_FIELD gives the geomagnetic field strength on x/y/z.
For more read Position Sensors.
Making your own Mock GPS (Local PS to be exact). I don't have a link for this but its definitely possible. Check out how GPS works to get an idea. Wifi and Bluetooth are signals. but you know what else is a signal?
A: SOUND
make each phone make a large beep in turn and measure audio strength using receivers. This might work better than wifi/bluetooth. once you measure relative distances between every pair of phones, it only takes a good algorithm to find relative positions
A Possible Alternative Solution : use image processing. Get something like OpenCV for Android and setup one phone as a master. This will work only for a 2D Layout.
Another "idea" - use the cameras. Stick A board on top of your surface with 4 QR codes in each corner. (This will help identify the edges and orientation of your phone). If you're looking for a 3D layout and the phones have sufficient in-between space, you could stick a QR behind every phone and show a QR on the screen of every phone.
All of these are solutions. Maybe you can use individual ones. Maybe you can use a combination. who knows.
An idea, in case it's relevant for your use case:
Setup phase
start your app on each device in "pairing mode".
Each device will show a QR code containing the key required for communicating with the device (for example via Firebase), and screen details: size in pixels. It will also draw a rectangle at the screen boundaries.
A different phone, external to this layout will run your app as a "master", taking a picture of the phones from above.
Now you need to write an algorithm to identify the screens and their locations, orientation and extract the QR codes for analysis. Not easy, but doable.
Interaction phase
now all the phones (this should work on more than two phones) can collaborate screens to show parts of the same movie, for example.
Seems not, if You have only 2 devices, but if You have external sources (with known position) of any signal (audio, vibrate, BT or WiFi radio, etc.), which can be detected by devices with adequate accuracy, and devices time is synchronized, You can do this comparing time of signal start (or signal strength) on both devices like on this picture:
Or, if You can add some sensors to one of devices, You can create "other device locator", for example like this sound locator.
UPDATE
In a updated formulation, the issue is also not solvable: it's possible to determine which two devices are at the edge, but you can not determine which one is on the left and which is on the right side. It is necessary that at least one device knows that it, for example, is leftmost - then other devices, for example, generates a sound, the others receive it and determine their order according to the difference in arrival time. But the anchor point and synchronization of time are necessary.
By understating your use case, it is possible to find number of devices surrounded by host device, using Nearby Api, other techniques. But find how many devices each side!!! I don't think it is possible with the current mobile hardware and technology. Because, by considering all factors, magnetic sensors are only the least possible solution. But the current mobiles have no such capability.
The following point I made based on above answers.
TYPE_ACCELEROMETER, TYPE_LINEAR_ACCELERATION, TYPE_MAGNETIC_FIELD, TYPE_ORIENTATION these sensors are react to the magnetic field around the device (compass react to the magnet). You can try an app using TYPE_MAGNETIC_FIELD, test how it will react to other device when close to it (I think it will react).
But the point I am trying to make here is, if you put three devices to once side and 4 devices to other side, the MAGNETIC_FIELD sensor reads relative magnetic field. So we can't identify how may devices each side, Until unless you have made some scientific calculations.
The second point is, some one suggested TYPE_PROXIMITY sensor, but it is not meant to serve this purpose. Current mobiles, measures the proximity of an object in cm relative to the view screen of a device. This sensor is typically used to determine whether a handset is being held up to a person's ear.
Another least possibility is using location sensor, it can identify the coordinates relative to your device coordinates, you communicate between each device coordinates with host using NFC. But the problem is, your use case says those devices are very close to each other, so it is not measurable distance using location service.
To conclude, it is not possible to identify number of each devices each side of a host device, with the current mobile hardware. It will can archived by using external sensor that will extends the mobile capability. For example, a phone case that equipped with such a capability, this will open window to other use-cases and application as well.
I think a way but it may require a a bit work. First check if 2 devices are laying by getting device orientation and using accelerometer or rotation vector to check pitch, roll, etc.
When you are sure that they are laying send data from one device from one to another using BT or wifi. Data should include send time. Check retreive time on other device also you should check for latency for sending and retreiving data. If you can have a noticible time differences in ms for small distance differences between devices it would be easy to check how approximately close they are. Also you may ask users to hold their device 1 meter or fixed distance from each other to get a time of travel for BT or wifi signal you send to other.
Related
In my app,I use ble(Bluetooth Low Energy) to scan and connect to a nearest bluetooth device(There exists two similar bluetooth devices nearby).I use RSSI to make sure which is nearest and in most cases,it works fine.But I find it not 100% correct when the distances are short.During my test,one is 2 meters away from me and the other is 3 meters,and the RSSI of the farther one comes to be bigger,about 1 in 10 times.Is there any better idea to replace RSSI?
Your problem is very well known and it appears in any localization algorithm using ble beacons. Even if two devices are very close together, they may have different RSSI value due to the Fast fading effect.
The Fast fading originates due to effects of constructive and destructive interference patterns which is caused due to multipath.
To mitigate this problem, you can :
Compare the RSSI during a longer time. Especially if things are moving around, the radio-waves may interfere in a different way. If your receiver is a smartphone for example, the user is not static and a few more RSSI sample will give you a more accurate results.
Add spacial diversity. This can be done by adding another chip with another antenna that will also advertise. If the two antenna are not at the same place, you will have more RSSI data, coming from different path that will interfere in a different way. By doing the mean of the two value you should have better result (ideally combine with a longer acquisition time). But of course it is only possible if you are designing the hardware of the advertising device. Note that this can also allow your reciever to catch more adv for the same time-frame.
Frequency diversity. Make sure your advertiser is configured to use the 3 adv channels.
And of course if the two distances are very different the slow fading will be greater than any fast fading effect and you should not have any trouble.
-- Background:
We are working on a device called Run-n-Read which tracks a user's head movements and translates it to the appropriate text movement on the screen. The use is to help a person read while running on a treadmill or riding in a moving vehicle. You can check a small video on http://weartrons.com.
We have created a small device which contains accelerometer, a micro-controller and bluetooth to send the head location in real time to the tablet every ~17ms to match with the 60fps of display. We used Processing IDE to create a basic app with downloaded book pages to test the prototype.
-- PROBLEM:
We would like to run our app in the background and dynamically change the display coordinates of any other app contents on the screen, whether it's an eBook or twitter etc. Basically our algorithms are running on our external device and sending the display coordinates (in pixels to move up-down left-right) at about 60 times per second. We would like the Android display origin to move by that many pixels during every frame rendering.
I am an electronics engineer and it's my first stab at writing any piece of software, so please let me know if I was not clear or the answer is too obvious.
Android as OS makes sure applications are encapsulated and oblivious from each other. All inter-app communication is done through what is called intents which are in the end messages. And you have to know exactly the other apps declared intents and on top of that you have no assurances that all apps implemented the kind of feature you are requesting.
Therefore I don't think what you want to do (the coordinates change) is possible at all without tinkering with the OS source code and compiling your own version of Android.
I want to calculate distance Bluetooth Paired device from android mobile. I am new in Android Bluetooth Concept can any one suggest me it's possible or not possible in android sdk.if it's possible post any code or tutorial link!
The Bluetooth signal strength distance relation depends on the devices (built-in Bluetooth device, antenna, actual orientation of device), current way the persons hold their devices, objects in-between... You could measure this for a pair of devices for a given situation and use these information.
A larger and more general solution would incorporate an external Bluetooth network. Bluetooth triangulation is the basic concept, that will help. The link will give an insight on certainties that are achievable with such a setup. Take is as an upper limit, a device to device approach will be worse.
The EE Stack Exchange site has a more complete answer which includes a mention of Apple using 802.11v for determining if Apple Watch is close to a MacBook.
Bluetooth uses radio, and radio travels at the speed of light. A 1cm round trip will take less than 100ps. Timing something that short will be tricky, probably you'll want a 10GHz clock, though there are other options. But even then, Bluetooth isn't designed to instantly echo the radio message. If you receive, process and re-transmit the message, then the processing delay will be much longer than the time of flight, and will vary randomly by at least the period of the clock used with the Bluetooth chip.
You can't. Maybe, you can get approximate value from signal indicator but it's too much subject because of envirounment - is there something between connected devices, some reflection surfaces, etc.
There is a way you can research, is coding a response time. just calculate the bluethooth response time in nano secs, physically measure the distance between the devices and make a tree rule... is the same concept of GPS. This is a Laboratory work. I have a project that i have to develop it, in schedule i will taking it in a month.
OFC, its possible. It just requires ultra precise app, build to calculate "pings" between the two objects - kinda like ekko-location or laser distance measurement - its about how much time a specific signal travels back and forth.
Considering I have two smartphones, A and B. If I am holding smartphone A, is there a way to determine the location of B in relation to myself?
So if we had the situation of this image:
:
it would tell me B is at position (2, 1).
Inventive methods like using the strength of wifi signals to get position are more then welcomed. Could I also determine if there is a wall between the two phones?
As far as I understand, both Bluetooth and Wi-Fi signals move in a radial wave in all directions - so while you may be able to measure the distance between the two terminals, I doubt this would give you a correct reading, since it could either be on your "side" of the circular area or another one equidistant to the source of the signal.
While GPS may be the obvious solution since it provides exactly what you're looking for, I'm not sure if you're including this as an option. Once you get the two coordinate sets for the devices, it's a matter of calculating the offset (N/S and E/W) from device 1.
This makes me think on the accuracy given by GPS, which considering that you were including the tag Bluetooth in the question and since Bluetooth has a range of around 15-30 feet (type 2-3) and the GPS has an error margin of 25-35 feet, this may not be good either.
If you do manage to get a connection (Bluetooth) between the two devices, you'd already know your in that range, but not in what direction. You can get a signal strength measure from Android 2.1: How do I poll the RSSI value of an existing Bluetooth connection? but there-again I'm not sure as to how to detect in what direction the user is relative to you, just how close he is, in any direction. Hell the other device could be on top of you or under you and you'd get virtually the same reading as next to you given equal distances.
This is all on a "static" approach, meaning both devices are stationary. However if you measure that value and then take a step to your left and re-measure you can tell if you're closer or further away from the source, so with a little trial and error of one of the devices moving you could determine a relative position, this however may not be useful for you since you'd either need to tell the phone manually that you moved left and to re-measure or use something more complicated like monitoring the accelerometer of the phone which could tell in what direction the phone moved and map the strength of the signal.
Am I losing my mind? Probably.
No answer as far as I'm concerned for now, just thoughts. Depending on what the application will do, there may be other viable approaches. This is my brain-dump answer so hopefully someone else can read it and come up with a more elaborate answer instead of rumbling thoughts.
If the distance from A to B is more than a few metres, then if you can get the GPS location of both A & B, you can easily calculate distance and bearing between them using the Location.distanceTo() and Location.bearingTo() methods.
Depending on the physical environment, it is probable that two GPSs which are physically close together will be using the same satellites for calculation, and that the errors will be similar in both. So in some cases using GPS may work for small distances.
I'm making an application that works as a compass..
I'm using the accelerometer and the magnetic field sensors to compute the azimuth angle through, sensor.getOrientation().
I'm searching for something that can improve the magnetic field sensor accuracy, since I'm getting it state of accuracy as UNRELIABLE!
Any one knows anything about this?I'm looking for something that can be either hardcoded or for instance just physically moving the phone until it gets calibrated!
This is not a final answer (I don't know anything for sure), but my understanding from online posts is that waving the phone around in a figure of 8 a few times while the compass is in use is supposed to trigger automatic recalibration. This is what the google maps app suggests, for example. I don't know whether this is dependent on application functionality (something in maps that detects the waving by accelerometer and triggers a recalibration), or something in the android stack, or something specific to per-phone implementations. Try it and see!
Eg discussion: http://androidforums.com/epic-4g-support-troubleshooting/217317-cant-get-compass-calibrate.html
This reference appears to suggest this per-axis / figure-8 rotation process is built-in functionality: http://m.eclipsim.com/gpsstatus/
And here another article that claims this is built-in functionality, and that you don't even need to be running a compass-consuming app for the recalibration to work: http://www.ichimusai.org/2009/06/20/how-to-calibrate-the-htc-magic-compass/
Just a few points
The figure 8 motion works sometimes and not others, I have no idea why, they really need to have some kind of code based way to check if the 8 motion worked (Assuming that the physical motion is actually required)
They also need a way to detect that calibration is required, I looked at the code for the accuracy output (the unreliable constant) and once they send it to you they will not send it again, so for instance if you calibrate but then come within a strong magnetic field it will not resend (not sure why they did that)
One not completely reliable way to detect ongoing issues is that you can also use the magnetic sensor output and do something like field=sqrt(x*x+y*y+z*z) and check that field falls between say 25 and 65 and then ask the user to calibrate if it does not.
The bottom line after testing 18 phones is that I would never depend on a Android based compass with the current crop of phones, accuracy would always be in question.
I have also found even if you are lucky and have a fairly reliable phone you can never be sure that it's calibrated without checking it against a real compass, which kind of defeats the purpose.
NOTE: On a lot of the mis-behaving phones we have found that the sensor writes a calibration file and a tmp file with the same name. If you delete those files and re-boot the phones the calibration file is recreated with zero'd values and the cold start and general calibration problems resolve themselves.
The bad news is that they are stored in /data/misc and require root privileges to get at (thanks Google & Sensor mfg!) so even though I suspect this would solve a lot of problems for a lot of developers it just is not viable from a marketplace app perspective.
I am developing for Android. I'm using Titanium Alloy as development tool with the Titanium Geolocation module.
I have only tested 2 devices [Galaxy Note and S4] against a commercial magnetic compass. Following a calibration process [tilt along the 3 axis] and using 2 different compass apps and the app I'm working on, the Android compass seems accurate enough for basic use ... correlation was good enough for my purpose anyway. I also found the device compass reading to be very sensitive to other magnetic and electrical field interference ... initial mistake I made was to use the compass feature whilst device was in a device protector with a magnetic closure facility [quite common on tabs] ... this interference is particularly strong. I thus need to suggest to users of my app to remove device protectors, keep device free of other electronics and then do standard calibration before initializing the app.
Another option is:
Go To sensors menu: #*0#*
Then if you see a red line in Magnetic Sensor section and a Need for Calibration you should recalibrate your compass.
How;
According those guys;
Turn the Samsung Galaxy Mini S5 around all of its axes until the red
line in the black circle changes color from red to blue. You can also
run through a motion that follows the shape of an 8. It may be that
several attempts are needed to calibrate the compass...