Find nearby users of an app (iPhone and Android)

Question

I am working on an app that has an iPhone version as well as an Android version.

My goal is...

• display a list of nearby users of my app (iPhone app users and Android app users). Lets say a list users which are currently within 1 mile or 2 miles radius and are currently using my app.
• This list will display on both apps, iPhone app and Android app.
• App will update the list when user clicks a Refresh button.

My question is...

• What is the best way to accomplish above stated goal? Do I need to periodically send current GPS location of all users of app from their Droids and iPhones to our web server?

To make my question more clear...

• I have an algorithm to find out the places/users within a given range (1 mile or 2 miles radius etc), so PLEASE DON'T TELL ME how to find users within a given range.
• I know how to get current location of iPhone and Droid devices, so PLEASE DON'T TELL ME how to get updated location of an iPhone or Android device.
• I know that this is a privacy issue. Therefore app will ask for user's permission to send their location to our web server, so PLEASE DON'T TELL ME about privacy concerns users or Apple may have.
• JUST TELL ME how to best maintain updated list of Geo Locations of my app users on the web server? The best, proven approach!
• Let me know if my question still needs clarification.

Thanks and best regards

Answer 1

Even i had this question on my mind today while creating similar app. Alert when two users/friends are near to each other - Android Proximity

after spending a couple of hours thinking, I thought a better way to do this :

1) Create SharedPreference / DB which holds the last Coordinates of the device which was also updated to the server.

2) Create Service which will fire once in 15 minutes requesting current location.

3) If the current location matches the Last Location retrieved from the SharedPreference and or around within proximity (depends on how much u give 30ft or more) then user is in the same place so don't upload the coordinates to the server.

4) If the user isn't within proximity or last location doesn't match current location then upload the coordinates to the server.

5) After uploading coordinates to the server, update SharedPreference too..

6) After uploading, return response of Users details from the server who are nearby the same coordinates. The User will then get notified if someone around them..