CODEWITHSUNDEEP
ruby-on-railsruby-on-rails-3pluginsrubygemsgeolocation
Mohit Jain
Mohit Jain

Reputation: 43919

Fetch results based upon distance, using latitude and longitude stored in database

I have a User Model and every user is having latitude and longitude stored in the table. I want to fetch all the users in the range of 30kms with a given latitude and longitude. Any plugin to calculate the distance using latitude and longitude from the table.

id   name   latitude  longitude

 1   abc    43.56     56.34

 2   xyz    46.34     57.87

 3   mno    50.34     23.56

Assume this is my table values(its just a sample data.). I want to fetch all the users within a range of 30kms from a given altitude like (34.89, 56.45)

Upvotes: 0

Views: 3252

Answers (4)

ugiflezet
ugiflezet

Reputation: 451

Using the help from Movable-Type Scripts that Wicked posted i made this calculate the distance between 2 points (use method in an Active Record that has lat,lng attributes):

def calc_distance(origin)
  radius = 6371
  lat1 = to_rad(origin[0])
  lat2 = to_rad(self.lat)
  lon1 = to_rad(origin[1])
  lon2 = to_rad(self.lng)
  dLat = lat2-lat1   
  dLon = lon2-lon1

  a = Math::sin(dLat/2) * Math::sin(dLat/2) +
       Math::cos(lat1) * Math::cos(lat2) * 
       Math::sin(dLon/2) * Math::sin(dLon/2);
  c = 2 * Math::atan2(Math::sqrt(a), Math::sqrt(1-a));
  d = radius * c
end

def to_rad angle
  angle * Math::PI / 180 
end

Geokit is very robust but I only needed to calculate distance, plus Geokit requires a non sqlite db

Upvotes: 1

Evgeny Shadchnev
Evgeny Shadchnev

Reputation: 7388

There is beautiful Geokit gem that add this method to your models:

Store.find(:all, :origin =>[37.792,-122.393], :within=>10)

or even

Store.find(:all, :origin=>'100 Spear st, San Francisco, CA', :within=>10)

Upvotes: 3

Andrew Nesbitt
Andrew Nesbitt

Reputation: 6046

Thinking sphinx has search, sort and filtering by distance from a latitude and longitude: http://freelancing-god.github.com/ts/en/geosearching.html

Upvotes: 1

Wicked Coder
Wicked Coder

Reputation: 1118

Try this link. There is a detailed explanation of the approach.

http://www.movable-type.co.uk/scripts/latlong.html

Also, I found this C# algorithm online. I hope it helps.

class DistanceAlgorithm
{
    const double PIx = 3.141592653589793;
    const double RADIO = 6378.16;

    /// <summary>
    /// This class cannot be instantiated.
    /// </summary>
    private DistanceAlgorithm() { }

    /// <summary>
    /// Convert degrees to Radians
    /// </summary>
    /// <param name="x">Degrees</param>
    /// <returns>The equivalent in radians</returns>
    public static double Radians(double x)
    {
        return x * PIx / 180;
    }

    /// <summary>
    /// Calculate the distance between two places.
    /// </summary>
    /// <param name="lon1"></param>
    /// <param name="lat1"></param>
    /// <param name="lon2"></param>
    /// <param name="lat2"></param>
    /// <returns></returns>
    public static double DistanceBetweenPlaces(
        double lon1,
        double lat1,
        double lon2,
        double lat2)
    {
        double dlon = lon2 - lon1;
        double dlat = lat2 - lat1;

        double a = (Math.Sin(dlat / 2) * Math.Sin(dlat / 2)) + Math.Cos(lat1) * Math.Cos(lat2) * (Math.Sin(dlon / 2) * Math.Sin(dlon / 2));
        double angle = 2 * Math.Atan2(Math.Sqrt(a), Math.Sqrt(1 - a));
        return angle * RADIO;
    }

Upvotes: 0

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