Clusters of Lat, Long that are near to each other

Question

I have a scenario where N number of items were delivered at N locations (lat, long). I want to find group of items which are delivered near to each other(100 meters). Say for example (Item1, Item9,...Item499) were delivered such that they had distance less than 100 between them. Item9 can be more than 100 meters away from Item499 but it will be in that group if it has less than 100 meters distance from any one of the item in the group.

Find all such groups. I want someone to point out the right algorithm. I'll then work on that. Preferable Language is C#

Answer 1

Below is the algorithm to solve this problem which I found here

public class ClusterCreator
{
    public Dictionary<int, SimpleCluster> GetClusters(List<SimpleCluster> clusterList, int maxDistance)
    {
        //LOAD DATA
        //var clusterList = new List<SimpleCluster>(); // LoadSimpleClusterList();
        //var latitudeSensitivity = 3;
        //var longitutdeSensitivity = 3;

        //CLUSTER THE DATA
        return ClusterTheData(clusterList, maxDistance);
    }

    public Dictionary<int, SimpleCluster> ClusterTheData(List<SimpleCluster> clusterList, int maxDistance)
    {
        //CLUSTER DICTIONARY
        var clusterDictionary = new Dictionary<int, SimpleCluster>();

        //Add the first node to the cluster list
        if (clusterList.Count > 0)
        {
            clusterDictionary.Add(clusterList[0].ID, clusterList[0]);
        }

        //ALGORITHM
        for (int i = 1; i < clusterList.Count; i++)
        {
            SimpleCluster combinedCluster = null;
            SimpleCluster oldCluster = null;
            foreach (var clusterDict in clusterDictionary)
            {
                //Check if the current item belongs to any of the existing clusters
                if (CheckIfInCluster(clusterDict.Value, clusterList[i], maxDistance))
                {
                    //If it belongs to the cluster then combine them and copy the cluster to oldCluster variable;
                    combinedCluster = CombineClusters(clusterDict.Value, clusterList[i]);
                    oldCluster = new SimpleCluster(clusterDict.Value);
                }
            }

            //This check means that no suitable clusters were found to combine, so the current item in the list becomes a new cluster.
            if (combinedCluster == null)
            {
                //Adding new cluster to the cluster dictionary 
                clusterDictionary.Add(clusterList[i].ID, clusterList[i]);
            }
            else
            {
                //We have created a combined cluster. Now it is time to remove the old cluster from the dictionary and instead of it add a new cluster.
                clusterDictionary.Remove(oldCluster.ID);
                clusterDictionary.Add(combinedCluster.ID, combinedCluster);
            }
        }
        return clusterDictionary;
    }

    public static SimpleCluster CombineClusters(SimpleCluster home, SimpleCluster imposter)
    {
        //Deep copy of the home object
        var combinedCluster = new SimpleCluster(home);
        combinedCluster.LAT_LON_LIST.AddRange(imposter.LAT_LON_LIST);
        combinedCluster.NAMES.AddRange(imposter.NAMES);

        //Combine the data of both clusters
        //combinedCluster.LAT_LON_LIST.AddRange(imposter.LAT_LON_LIST);
        //combinedCluster.NAMES.AddRange(imposter.NAMES);

        //Recalibrate the new center
        combinedCluster.LAT_LON_CENTER = new LAT_LONG
        {
            LATITUDE = ((home.LAT_LON_CENTER.LATITUDE + imposter.LAT_LON_CENTER.LATITUDE) / 2.0),
            LONGITUDE = ((home.LAT_LON_CENTER.LONGITUDE + imposter.LAT_LON_CENTER.LONGITUDE) / 2.0)
        };

        return combinedCluster;
    }

    public bool CheckIfInCluster(SimpleCluster home, SimpleCluster imposter, int maxDistance)
    {
        foreach (var item in home.LAT_LON_LIST)
        {
            var sCoord = new GeoCoordinate(item.LATITUDE, item.LONGITUDE);
            var eCoord = new GeoCoordinate(imposter.LAT_LON_CENTER.LATITUDE, imposter.LAT_LON_CENTER.LONGITUDE);
            var distance = sCoord.GetDistanceTo(eCoord);
            if (distance <= maxDistance)
                return true;
        }
        return false;


        //if ((home.LAT_LON_CENTER.LATITUDE + latitudeSensitivity) > imposter.LAT_LON_CENTER.LATITUDE
        //       && (home.LAT_LON_CENTER.LATITUDE - latitudeSensitivity) < imposter.LAT_LON_CENTER.LATITUDE
        //       && (home.LAT_LON_CENTER.LONGITUDE + longitutdeSensitivity) > imposter.LAT_LON_CENTER.LONGITUDE
        //       && (home.LAT_LON_CENTER.LONGITUDE - longitutdeSensitivity) < imposter.LAT_LON_CENTER.LONGITUDE
        //   )
        //{
        //    return true;
        //}
        //return false;
    }

}
public class SimpleCluster
{
    #region Constructors
    public SimpleCluster(int id, string name, double latitude, double longitude)
    {
        ID = id;
        LAT_LON_CENTER = new LAT_LONG
        {
            LATITUDE = latitude,
            LONGITUDE = longitude
        };
        NAMES = new List<string>();
        NAMES.Add(name);
        LAT_LON_LIST = new List<LAT_LONG>();
        LAT_LON_LIST.Add(LAT_LON_CENTER);
    }

    public SimpleCluster(SimpleCluster old)
    {
        ID = old.ID;
        LAT_LON_CENTER = new LAT_LONG
        {
            LATITUDE = old.LAT_LON_CENTER.LATITUDE,
            LONGITUDE = old.LAT_LON_CENTER.LONGITUDE
        };
        LAT_LON_LIST = new List<LAT_LONG>(old.LAT_LON_LIST);
        NAMES = new List<string>(old.NAMES);
    }
    #endregion
    public int ID { get; set; }
    public List<string> NAMES { get; set; }
    public LAT_LONG LAT_LON_CENTER { get; set; }
    public List<LAT_LONG> LAT_LON_LIST { get; set; }
}

public class LAT_LONG
{
    public double LATITUDE { get; set; }
    public double LONGITUDE { get; set; }
}

Answer 2

The answer above works for me. Thank you

If anyone has issues with the GeoCoordinate class, meaning your compiler doesnt find it, you can just use the classes from here: https://github.com/ghuntley/geocoordinate There are under geocoordinate/src/GeoCoordinatePortable/, and the scripts are GeoCoordinate.cs and GeoPosition.cs