Module: Geocoder::Sql

Extended by:
Sql
Included in:
Sql
Defined in:
lib/geo-calculator/sql.rb

Instance Method Summary collapse

Instance Method Details

#approx_bearing(latitude, longitude, lat_attr, lon_attr, options = {}) ⇒ Object

Totally lame bearing calculation. Basically useless except that it returns something in databases without trig functions.



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# File 'lib/geo-calculator/sql.rb', line 94

def approx_bearing(latitude, longitude, lat_attr, lon_attr, options = {})
  "CASE " +
    "WHEN (#{lat_attr} >= #{latitude.to_f} AND " +
      "#{lon_attr} >= #{longitude.to_f}) THEN  45.0 " +
    "WHEN (#{lat_attr} <  #{latitude.to_f} AND " +
      "#{lon_attr} >= #{longitude.to_f}) THEN 135.0 " +
    "WHEN (#{lat_attr} <  #{latitude.to_f} AND " +
      "#{lon_attr} <  #{longitude.to_f}) THEN 225.0 " +
    "WHEN (#{lat_attr} >= #{latitude.to_f} AND " +
      "#{lon_attr} <  #{longitude.to_f}) THEN 315.0 " +
  "END"
end

#approx_distance(latitude, longitude, lat_attr, lon_attr, options = {}) ⇒ Object

Distance calculation for use with a database without trigonometric functions, like SQLite. Approach is to find objects within a square rather than a circle, so results are very approximate (will include objects outside the given radius).

Distance and bearing calculations are *extremely inaccurate*. To be clear: this only exists to provide interface consistency. Results are not intended for use in production!



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# File 'lib/geo-calculator/sql.rb', line 34

def approx_distance(latitude, longitude, lat_attr, lon_attr, options = {})
  units = options[:units] || Geocoder.config.units
  dx = Geocoder::Calculations.longitude_degree_distance(30, units)
  dy = Geocoder::Calculations.latitude_degree_distance(units)

  # sin of 45 degrees = average x or y component of vector
  factor = Math.sin(Math::PI / 4)

  "(#{dy} * ABS(#{lat_attr} - #{latitude.to_f}) * #{factor}) + " +
    "(#{dx} * ABS(#{lon_attr} - #{longitude.to_f}) * #{factor})"
end

#full_bearing(latitude, longitude, lat_attr, lon_attr, options = {}) ⇒ Object

Fairly accurate bearing calculation. Takes a latitude, longitude, and an options hash which must include a :bearing value (:linear or :spherical).

Based on: www.beginningspatial.com/calculating_bearing_one_point_another



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# File 'lib/geo-calculator/sql.rb', line 65

def full_bearing(latitude, longitude, lat_attr, lon_attr, options = {})
  degrees_per_radian = Geocoder::Calculations::DEGREES_PER_RADIAN
  case options[:bearing] || Geocoder.config.distances
  when :linear
    "MOD(CAST(" +
      "(ATAN2( " +
        "((#{lon_attr} - #{longitude.to_f}) / #{degrees_per_radian}), " +
        "((#{lat_attr} - #{latitude.to_f}) / #{degrees_per_radian})" +
      ") * #{degrees_per_radian}) + 360 " +
    "AS decimal), 360)"
  when :spherical
    "MOD(CAST(" +
      "(ATAN2( " +
        "SIN( (#{lon_attr} - #{longitude.to_f}) / #{degrees_per_radian} ) * " +
        "COS( (#{lat_attr}) / #{degrees_per_radian} ), (" +
          "COS( (#{latitude.to_f}) / #{degrees_per_radian} ) * SIN( (#{lat_attr}) / #{degrees_per_radian})" +
        ") - (" +
          "SIN( (#{latitude.to_f}) / #{degrees_per_radian}) * COS((#{lat_attr}) / #{degrees_per_radian}) * " +
          "COS( (#{lon_attr} - #{longitude.to_f}) / #{degrees_per_radian})" +
        ")" +
      ") * #{degrees_per_radian}) + 360 " +
    "AS decimal), 360)"
  end
end

#full_distance(latitude, longitude, lat_attr, lon_attr, options = {}) ⇒ Object

Distance calculation for use with a database that supports POWER(), SQRT(), PI(), and trigonometric functions SIN(), COS(), ASIN(), ATAN2(), DEGREES(), and RADIANS().

Based on the excellent tutorial at: www.scribd.com/doc/2569355/Geo-Distance-Search-with-MySQL



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# File 'lib/geo-calculator/sql.rb', line 13

def full_distance(latitude, longitude, lat_attr, lon_attr, options = {})
  units = options[:units] || Geocoder.config.units
  earth = Geocoder::Calculations.earth_radius(units)

  "#{earth} * 2 * ASIN(SQRT(" +
    "POWER(SIN((#{latitude.to_f} - #{lat_attr}) * PI() / 180 / 2), 2) + " +
    "COS(#{latitude.to_f} * PI() / 180) * COS(#{lat_attr} * PI() / 180) * " +
    "POWER(SIN((#{longitude.to_f} - #{lon_attr}) * PI() / 180 / 2), 2)" +
  "))"
end

#within_bounding_box(sw_lat, sw_lng, ne_lat, ne_lng, lat_attr, lon_attr) ⇒ Object 



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# File 'lib/geo-calculator/sql.rb', line 46

def within_bounding_box(sw_lat, sw_lng, ne_lat, ne_lng, lat_attr, lon_attr)
  spans = "#{lat_attr} BETWEEN #{sw_lat} AND #{ne_lat} AND "
  # handle box that spans 180 longitude
  if sw_lng.to_f > ne_lng.to_f
    spans + "#{lon_attr} BETWEEN #{sw_lng} AND 180 OR " +
    "#{lon_attr} BETWEEN -180 AND #{ne_lng}"
  else
    spans + "#{lon_attr} BETWEEN #{sw_lng} AND #{ne_lng}"
  end
end