How to generate random locations nearby my location?

I am trying to create random locations nearby my location. What i want is to create random latitude/longitude pairs inside a 200 meters circle surrounding my location.

This is the formula i came up with (with the help of people at StackOverFlow): (Random number between -1 and 1)*radius + (old longitude) = new longitude within radius of old longitude

(Random number between -1 and 1)*radius + (old latitude) = new latitude within radius of old latitude

The thing is that something weird is happening with my implementation because all the random locations are too near of my location center, it seems that the formula does not cover the whole radius.

Any idea of what could be wrong with my formula?

Edited to show the current java implementation:

public static Location getLocation(Location location, int radius) {
    Random random = new Random();

    // Convert radius from meters to degrees
    double radiusInDegrees = radius / METERS_IN_DEGREES;

    double x0 = location.getLongitude() * 1E6;
    double y0 = location.getLatitude() * 1E6;
    double u = random.nextInt(1001) / 1000;
    double v = random.nextInt(1001) / 1000;
    double w = radiusInDegrees * Math.sqrt(u);
    double t = 2 * Math.PI * v;
    double x = w * Math.cos(t);
    double y = w * Math.sin(t);

    // Adjust the x-coordinate for the shrinking of the east-west distances
    double new_x = x / Math.cos(y0);

    // Set the adjusted location
    Location newLocation = new Location("Loc in radius");
    newLocation.setLongitude(new_x + x0);
    newLocation.setLatitude(y + y0);

    return newLocation;
}

I am not sure what i am doing wrong, because the new locations are created in the middle of the sea 🙂

Any idea? thank you

 

Answer:—

The correct implementation is:

public static void getLocation(double x0, double y0, int radius) {
    Random random = new Random();

    // Convert radius from meters to degrees
    double radiusInDegrees = radius / 111000f;

    double u = random.nextDouble();
    double v = random.nextDouble();
    double w = radiusInDegrees * Math.sqrt(u);
    double t = 2 * Math.PI * v;
    double x = w * Math.cos(t);
    double y = w * Math.sin(t);

    // Adjust the x-coordinate for the shrinking of the east-west distances
    double new_x = x / Math.cos(y0);

    double foundLongitude = new_x + x0;
    double foundLatitude = y + y0;
    System.out.println("Longitude: " + foundLongitude + "  Latitude: " + foundLatitude );
}

I removed the dependency on external libraries to make it more accessible.

 

SELECT * FROM(
    SELECT *,(((acos(sin((@latitude*pi()/180)) * sin((Latitude*pi()/180))+cos((@latitude*pi()/180)) * cos((Latitude*pi()/180)) * cos(((@longitude - Longitude)*pi()/180))))*180/pi())*60*1.1515*1.609344) as distance FROM Distances) t
WHERE distance <= @distance



SELECT * , 6371.04 * ACOS( COS( PI( ) /2 - RADIANS( 90 - Latitude) ) * COS( PI( ) /2 - RADIANS( 90 - '$latitude' ) ) * COS( RADIANS( Longitude) - RADIANS( '$longitude' ) ) + SIN( PI( ) /2 - RADIANS( 90 - Latitude) ) * SIN( PI( ) /2 - RADIANS( 90 - '$latitude' ) ) ) AS Distance FROM MyLocations WHERE ( 6371.04 * ACOS( COS( PI( ) /2 - RADIANS( 90 - Latitude) ) * COS( PI( ) /2 - RADIANS( 90 - '$latitude' ) ) * COS( RADIANS( Longitude) - RADIANS( '$longitude' ) ) + SIN( PI( ) /2 - RADIANS( 90 - Latitude) ) * SIN( PI( ) /2 - RADIANS( 90 - '$latitude' ) ) ) <1 ) GROUP BY one_id HAVING dist < '$radius' ORDER BY Distance LIMIT 0 , $numberOfResults

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s