hexagonal circle packing

circle_pack_example.java

//wrote this for more efficient scanning of nearby pokemon, 
//gets centroids for 7 minimally overlapping circles in a hexagon
//shape around an origin point
//to get a bigger area, just recurse this and de-dupe returned centroids
//for each pass
//this was in java for android, but python code is nearly identical
public static List<LatLng> pointsToScan(LatLng origin) {
    double origin_lat = origin.latitude;
    double origin_lng = origin.longitude;

    List<LatLng> points = new ArrayList<>();
    points.add(origin);

    double scanRadius = 0.1; //100m
    float R = 6379.1f;
    int[] nearby_dirs = {0, 60, 120, 180, 240, 300};
    float d = (float) (Math.sqrt(3) * scanRadius); //dist to center of next circle
    for (int direction: nearby_dirs) {
        double bearing = Math.toRadians(direction);
        double lat1 = Math.toRadians(origin_lat);
        double lng1 = Math.toRadians(origin_lng);
        double lat2 = Math.asin( Math.sin(lat1)*Math.cos(d/R) +
                Math.cos(lat1)*Math.sin(d/R)*Math.cos(bearing));
        double lng2 = lng1 + Math.atan2(Math.sin(bearing)*Math.sin(d/R)*Math.cos(lat1),
                Math.cos(d/R)-Math.sin(lat1)*Math.sin(lat2));
        lat2 = Math.toDegrees(lat2);
        lng2 = Math.toDegrees(lng2);

        points.add(new LatLng(lat2, lng2));
    }
    return points;
}

Example of circles generated from these points: