iOS Find Other Nearby Devices (GPS locations)

Question

I have an app that allows a user to transmit their location to a server. What I am trying to do is have the user press a button that will send a push notification to anyone with the app within lets say a 3 mile radius. Can someone give me an overview of how I can accomplish this.

The only way I could think of doing this is publishing the gps coords to a server. Then when the user presses "Send notif" a message gets sent to the server, then the server does some complex proximity search based upon the location and then returns the values to the user.

My problem is, I have no server-side experience and have no idea how to program a GPS search algorithm on the server.

Is there a way for me to do what I want without having to write code on a server? I am able to use Parse to store the GPS coordinates. I'd like to keep my server code to simply storing and retrieving values and handle everything else client side.

Thoughts?

Answer 1

Each device should send their GPS coordinates to the server periodically. I think you already have this step. The next step is to find devices that are near each other. This is fairly simple.

Distance Between Two Latitude and Longitude Points

However, if you have millions of devices, it will be a problem of scale if you compare each update to all the other devices. You might bucket the devices to a certain area. For example, you might bucket the updates into 100 square mile areas. When an update comes in you need to only compare to those devies in that bucket plus adjacent buckets if they are near the edge. This is just top of the head analysis but hopefully it will point you in the right direction.