module Geocoder::Sql

def approx_bearing(latitude, longitude, lat_attr, lon_attr, options = {})


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

def approx_distance(latitude, longitude, lat_attr, lon_attr, options = {})


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

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

def full_bearing(latitude, longitude, lat_attr, lon_attr, options = {})


http://www.beginningspatial.com/calculating_bearing_one_point_another
Based on:

SIN(), COS(), ASIN(), ATAN2().
For use with a database that supports MOD() and trigonometric functions

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

def full_distance(latitude, longitude, lat_attr, lon_attr, options = {})


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

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

def within_bounding_box(sw_lat, sw_lng, ne_lat, ne_lng, lat_attr, lon_attr) 

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