Check if a GPS location is within a certain radius of another GPS location in android

Question

I'm developing an Android app which takes the user's current location and shows other users' gps locations on a map which falls with a certain radius, say 20 kilometers.

For example, if I am the user, I want to see other users' locations plotted on a map who are within a radius of 20 kilometers from my location.

I am able to save my location, other users' locations and plot them on map also. I am not able to figure out if those users fall in 20 kilometers radius from my location or not.

I use Google Maps Android API v2 to plot locations on map and Parse for saving the GPS locations (latitude and longitude coordinates)

I Googled for solutions but in vain. Could anyone please provide a hint or reference or sample code on how to check if a GPS location is within a certain radius of another GPS location or not.

Any help will be appreciated.

Solution 1

It's very easy. When you add Marker into your Map just get distance from that Marker to your Current Location if distance is <= 20 then add that marker into Map. Like so

float[] results = new float[1];
Location.distanceBetween(oldPosition.latitude, oldPosition.longitude,
            newPosition.latitude, newPosition.longitude, results);

Solution 2

First get distance between 2 position:

float[] distance = new float[1];
Location.distanceBetween(oldPosition.latitude, oldPosition.longitude,
        currentPosition.latitude, currentPosition.longitude, distance);

distance will be in meter.

So, we have to convert our designer radius (20 KM) distance in meter to compare.

double radiusInMeters = 20.0*1000.0; //1 KM = 1000 Meter

New we can check that current position is inside 20 KM radius or not using...

if( distance[0] > radiusInMeters ){
    Toast.makeText(getBaseContext(), 
    "Outside, distance from center: " + distance[0] + " radius: " + radiusInMeters, 
    Toast.LENGTH_LONG).show();
} else {
    Toast.makeText(getBaseContext(), 
    "Inside, distance from center: " + distance[0] + " radius: " + radiusInMeters , 
    Toast.LENGTH_LONG).show();
}

Comments

[athira09]

What is results used for? Can you just explain.

[M D]

@athi09 results variable contains distance.

[athira09]

why is it float[1] ?

[M D]

@athi09 Just and array with two elements

[M D]

http://stackoverflow.com/questions/22093792/android-google-m‌​ap-find-distance-bet‌​ween/22093862#220938‌​62

[athira09]

Thank you M D. I'll just try this out and let you know the result

[athira09]

I'm getting some value. Is the results shown in meters?

[AlexWien]

@athi09 you should be able to find out yourself what value distancebetween delivers. Since it is an API function, just read the online docu.

[athira09]

distanceBetween(double startLatitude, double startLongitude, double endLatitude, double endLongitude, float[] results) Computes the approximate distance in meters between two locations, and optionally the initial and final bearings of the shortest path between them.

[athira09]

Thank you @Enamul but I already got the answer and I have accepted it too.