Im trying to develop an Android messenger application where a message is sent by user 1 to everyone using the app, the message contains the GPS location of user 1. Is it possible to determine the distance between user 1 and the user 2 and based on that either choose to display or discard the message. How do I go about it? Cloud you point out considerations that I might have missed out?
Another method I believe is possible is to periodically update a server with every users GPS location and then let the server decide who gets the message, but I would not like to use this method as it would be a privacy issue. No one would want their whereabouts being tracked by a server all day. Is there another solution to this?
You can use the haversine formula to determine the distance between two locations. Here is a link that provides the formula in various languages.
http://www.movable-type.co.uk/scripts/latlong.html
One way of doing this is to store the most recent location of a phone on the server in the database. You can then query the database (using a stored procedure) to determine who your closest neighbors (phones) are by setting a radius. For instance, show me all the phones within 500 meters.
Here is an example of how to do this:
http://www.movable-type.co.uk/scripts/latlong-db.html
Related
I did some search but could not find a suitable answer.
My App should compare with multiple locations for proximity. This means I will not be able to save all the locations into my app to confirm the proximity using locationManager. I want the proximity confirmation to be done in the server
What would be the best way to implement this?
Would it be sensible if the app asks for proximity confirmation every time the devices moves around?
I would try a different approach, since location updates from GPS are made once per second,
and I don't think it's a good idea to ask the server each second for proximity if you have a large amount of devices.
Think of this idea -
Get the device's initial location and send it to the server.
Decide on a sensible radius that the device will stay within it for the next 5-10 minutes.
Also make sure that you don't have "too many" points in that radius, or you can narrow the radius in that case.
It's up to you to decide the radius and the number of points, depending on your usage,
number of points etc.
Send form the server all the locations within that radius to the device.
Let the device calculate the proximity by itself.
When the device moves out of the initial radius - update the server and get the new
relevant locations.
This can be done easily - call the radius r. Save the initial location of the device, and calculate the distance
between the current and initail location. When it is "close enough" to r - update the server.
In your case, simply, you can send the received locations to your server and then make required calculations on server. But don't forget that you will be dealing with those questions
How many devices send location to server ?
How frequently each device send location to server ?
Also the responsibility of detecting a device has entered an area on the server
I think you can reduce the complexity of the all things by using geofencing api, link
No need to send each location to server.
Each device individually detects itself has entered or exited an
area.
EDIT
Otherwise you will be doing entered/exited calculations on server for unlimited count of device, whenever each device's location has changed.
Before we were doing similar thing in my previous company, calculating enter/exit time and enter durations. but via real gps devices on buses
We have almost 100 points(geofence) in city. So you can think that those points are on a few routes
Each gps device on bus is sending location to server periodically.
When the bus has finished it's route, server reviews device's all received locations on the route.
Compares each geofence with each location of bus.
This is the real scenario. You can call it "server based geofencing".
You could do a simple k-d tree implementation on the server side to store the coordinates.
Send the coordinates of the device over, which can be determined at whatever interval you need. If it's every 5 seconds, or 10 seconds it doesn't really matter. This will mainly be decided by the minimum distance between each of the coordinates/radius. If they're closer, you may need to update it more frequently.
Using the k-d tree finding the nearest neighbor would be O(log(n)). However, you make a slight modification where you can start adding the nodes to a list as long as they are within the certain radius of your device coordinates. In fact if you store it locally as a k-d tree as well then you can pick the furthest nodes in O(log(n))
Now on the second update when the device location is sent again, you can quickly update it since you have the existing locations. Say you move in the x direction by 5. You can drop the points that are now outside of the radius at x - 5. The new proximity, you do the same nearest neighbor search, adding in nodes as they're within the radius, but this time starting with the cached nodes closest to the direction you are moving in.
Combining that with an interval tree for radiuses. So say 0 to 1, 1 to 2, 2 to 3, as your intervals. You can pick out everything within a certain radius in O(log(n)) time as well. Those should be pointers to nodes in the k-d tree. That would simplify the radius calculations and finding the location if you're willing to sacrifice some memory for efficiency.
For a "fast" way to implement it on the server side you can use the mondodb $near geospatial query.
https://docs.mongodb.org/manual/reference/operator/query/near/
While on the mobile side you can use the minDistance property for the location updates. You can set it to a reasonable distance 20m/50m depending on the average distance between your locations.
http://developer.android.com/reference/android/location/LocationManager.html#requestLocationUpdates(java.lang.String,%20long,%20float,%20android.location.LocationListener)
There is a free service for this purpose -> Radar
You can register unlimited circle or polygon geofence, and register your user in app for tracking that user. When user entered in one geofence Radar send a notification to your server and send below data to you:
User ID, Geofence ID that user entered or exit, Confidence (low, medium, high) used for geofence that has overlap.
You can use this SDK in only 10 minutes.
I'm building a location based application.
Lets say that i have user A and i have a latitude and longitude values of his current location.
I got user B,C,D and thier locations as well..
For the example - user B + D are in a radius of 5km from user A and user C is in 12km radius from user A and I want to know how can i make a function that will tell me that whose near to me by 4/5/6/7km and etc..
If i user A wants users that are 8.5km away from him i will have as a result user B + D and thier distance from user A.
Now.. i know that i can use the Location class and use the distance function to calculate the distance between two users.
But the problem is that if i want to calculate that for the radius distance i need to fetch the entire users list from my database and send it to the client to start calculating distances between him and those i fetched from the server.
Now i dont want to do that off course if there is a better and more effecient way..
Firstly, I thought off using http request or some mathematical functions to calculate the distance between my users on the server side but the client (Android) offers very good tools to do so , so because of that I am lost of knowing to is the best thing to do.
Thanks head up :)
Hey don't you think that always sending locations of n-1 users to one requesting from server is inefficient and consumes unnecessary bandwidth than sending only few in the radius vicinity? The server can easily do this computation.
Think of a scenario where your app user base grows and grows? Then what?
Such a computation is always performed on the server.
Also nearly all of the times, server has much more computing power than the client. So even though android tools look lucrative, don't end up using those in a scenario like this.
In terms of tools, there are similar on the server side too ex. the haversine function. Also some databases like mongo also have inbuilt location filters. So this is really worth checking out.
I am looking for an easy way to check if a user is at my location (50m) radius if notify me.
Right now I have a service running every two minutes getting position of each user comparing it and then notifying if user in same location.
Can this be done using promixityalert: http://goo.gl/9I857T?
Thanks!
Instead ProximityAlert I would use Geofences.
http://developer.android.com/training/location/geofencing.html
Is newer and does a more effective use of the battery
In your case, you can have a service that sends to the other device the current location every X minutes, so it can update the Geofence. The problem that I see is that there would be a lot of calls, spending battery and the data plan.
A good approach is to use the Location Services API, you can detect if a user is standing or moving.
http://developer.android.com/training/location/activity-recognition.html
Using this and sending new locations only when the user is moving you will be able to reduce the amount of calls.
Parse is another option as #thepace mention. It is easy to use and whit it would be easy to implement what you are trying to do, but is not free :(
Hope it helps.
Issue: Check if any user (multiple and variable location) is within specific radius of my current location(variable).
Solution:
1. Parse.com
a) Ensure every user has their location updated in Parse DB including yours.
https://parse.com/tutorials/anywall-android
b) Use push notificaitons: https://parse.com/docs/push_guide#setup/Android
1> Create a channel wherein only you are subscribed.
2> Create your installation query and send notification to it to the channel subscribed.
I am currently studying a possible project on Android and iPhone.
I need to know if geofences could help me, or if another method should be used.
I think the geofence are not used in this way but I ask anyway.
Is it possible to place a geofence on the current user location (even if it moves) and sending messages when other people come on the geofence position (even they are 100 000) ?
Thank you very much in advance for your answers.
It's do-able but you will be lagging a lot...you will have to get a strong server to get all the positions of the users at a given time and place a listener on each user location s.t. in case his geolocation gets into some geofence every listener should inform its listenee (which will probable be the user class), so far should be good BUT hypothetically 1 user can get into millions other geofences (indicating your start-up is running quite good...) which will require the server to send millions of alert, now think on a million users moving - that means that even if you send just their location you can end up moving a couple of tera-bytes in a second to the server and from it plus requiring it to make more than trillions actions (probabley push notifications?) per second...
It depends on many variables as: radius of your geofences, quantity of users, etc. Notice, that in normal life you never approach 100000 people at one time, well, maybe at the football game. I think nothing is impossible, but a lot of factors need to be reviewed.
I'm developing an app that tracks the movement of public transport (buses and trams). I'm doing both, client and server side. The client requests the position of a bus from a server database and the server side is just a simple app that should send the current location to this server database every, lets say, 10 seconds for example.
Don't think about performance nor batery life, it doesn't matter. The important app is the one at the client side, the server side is just a simulation as how it should be in case we had real gps installed in every vehicle. So forget about batery life on server side.
I've read that there is a time interval limitation on Android to get location through network provider, and this limitation is set to 45 seconds min. Is it possible to skip this limitation in any way? Would it be better to use the phone GPS to achieve this task?
Regarding the database, I just store an ID (autoincrement) as primary key, latitude, longitude, and a timestamp.
I thought also about listening changes on location, and when there is a change, add a new entry to my database. If I want to check the position from the client side, I will look for the last entry with a timestamp equal or less than the current one. But if the limitation is set to 45 seconds, this approach won't help me either.
Thanks in advance.
You should be using the new "Fused Location Provider" from the recently added location services API in Google Play Services. There is a good walk through on how to accomplish this here. The nice thing about the new location API is you don't have to decide on GPS or Network. The internals of the API will determine which provider should be used to give you the most accurate location. Also, I've never heard anything about a limit to location updates. I'm pretty sure you can get them as fast as 1 update per second, don't quote me on that though.