Mismatch in rgeo spatial distance vis-a-vis reality

[srs...@gmail.com]

I am listing out nearby options from user location, in which distance plays a major role. I chose rgeo to filter me out those options within 10 kms radius using ST_DWithin. However, I am getting significant margins in rgeo computed distance with respect to google map results.

Tried with the following sample points so far, and my results:

• Origin: (Lat, Long) - 12.918269, 77.635669

• Table

      RGeo Distance                   Lat, Long              GMap
         (in m)                                            (in Kms)
  
    4865.012768186506,         12.960146,  77.648496          7.4         
    4865.012768186506,         12.960146,  77.648496          7.4         
    2286.5466828101517,        12.936992,  77.627002          2.7            
    3672.943407131079,         12.949931,  77.645193          7.8           
    7913.722140288826,         12.848925,  77.651733         11.7              
  

• Model:

  class Locate < ApplicationRecord
     scope :nearby, -> (origin, dist_in_meters = 10000) {
       where("ST_DWithin(ST_GeographyFromText('SRID=4326;#{origin}'), position, #{dist_in_meters})")
      } 
  end
  

• Controller:

  def nearby
    origin = geo_factory(77.635669,12.918269)
    options = Locate.nearby(origin)
    opt_dist = Array.new
      options.each do |option| 
        opt_dist << origin.distance(option.position)
      end
    render json: { options: options, distance: opt_dist }, status: 200
  end
  
  def geo_factory(ulong,ulat)
     RGeo::Geographic.spherical_factory(srid: 4326).point(ulong,ulat)
  end
  

• Schema:

   create_table "locates", force: :cascade do |t|
      t.integer   "user_id"
      t.geography "position",   limit: {:srid=>4326, :type=>"st_point", :geographic=>true}
      t.datetime  "created_at", null: false
      t.datetime  "updated_at", null: false
    end
  

• Initializer (rgeo.rb)

  RGeo::ActiveRecord::SpatialFactoryStore.instance.tap do |config|
  
      # By default, use the GEOS implementation for spatial columns.
       config.default = RGeo::Geos.factory_generator
  
      # But use a geographic implementation for point columns.
       config.register(RGeo::Geographic.spherical_factory(srid: 4326), geo_type: "point")
  end
  

Assuming distance calculated in rgeo represents shortest path between two points which might not be the case in reality, hence being differing with gmap results. Can someone share if they had any similar experience?

Thanks in advance!

Github: https://github.com/rgeo/rgeo/issues/171