Module: GeoFoo::Core

Defined in:
lib/geo_foo/core.rb

Class Method Summary collapse

Class Method Details

.create_table ⇒ Object

migration helper: create the database table



29
30
31
32
33
 
# File 'lib/geo_foo/core.rb', line 29

def self.create_table
  execute "CREATE TABLE #{TableName} (id serial PRIMARY KEY)"
  execute "SELECT AddGeometryColumn('#{TableName}', 'point', #{SRID}, 'POINT', 2)"
  execute "CREATE INDEX #{TableName}_point_index ON #{TableName} USING GIST (point)"
end

.drop_table ⇒ Object

migration helper: drop the database table



36
37
38
 
# File 'lib/geo_foo/core.rb', line 36

def self.drop_table
  execute "DROP TABLE #{TableName}"
end

.find_neighbours_by_coords(lat, lon, radius = 100.0) ⇒ Object

find all locations within a radius for a given location



17
18
19
20
21
22
23
24
25
26
 
# File 'lib/geo_foo/core.rb', line 17

def self.find_neighbours_by_coords lat, lon, radius=100.0
  # compute an appropriate bounding box size for this latitude
  # XXX handle case where lat is (close to) +-90deg (poles)
  bbox_size= (radius.to_f / (EarthRadius * Math.cos(lat.to_rad))).to_deg
  distance = "ST_Distance_Sphere(point, #{as_point(lat,lon)})"
  (execute "SELECT (id) FROM #{TableName} "\
           "WHERE ST_DWithin(#{as_point(lat,lon)}, point, #{bbox_size}) "\
           "AND #{distance} < #{radius} "\
           "ORDER BY #{distance}").map { |row| row["id"].to_i }
end