Module: Geokit::Mappable::ClassMethods

Defined in:
lib/geokit/mappable.rb

Overview

:nodoc:

Constant Summary collapse

PI_DIV_RAD = 
Math::PI / 180
EARTH_RADIUS_IN_METERS = 
6376772.71
METERS_PER_LATITUDE_DEGREE = 
111181.9
EARTH_RADIUS = 
{}
PER_LATITUDE_DEGREE = 
{}

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.register_unit(key, in_meters) ⇒ Object 



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# File 'lib/geokit/mappable.rb', line 155

def self.register_unit(key, in_meters)
  EARTH_RADIUS[key] = EARTH_RADIUS_IN_METERS * in_meters
  PER_LATITUDE_DEGREE[key] = METERS_PER_LATITUDE_DEGREE * in_meters
end

Instance Method Details

#decimal_to_dms(deg) ⇒ Object

Given a decimal degree like -87.660333 return a 3-element array like [ -87, 39, 37.198… ]



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# File 'lib/geokit/mappable.rb', line 132

def decimal_to_dms(deg)
  return false unless deg.is_a?(Numeric)
  # seconds is 0...3599.999, representing the entire fractional part.
  seconds = (deg.abs % 1.0) * 3600.0
  [
      deg.to_i,               # degrees as positive or negative integer
      (seconds / 60).to_i,    # minutes as positive integer
      (seconds % 60)          # seconds as positive float
  ]
end

#deg2rad(degrees) ⇒ Object 



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# File 'lib/geokit/mappable.rb', line 143

def deg2rad(degrees)
  degrees.to_f / 180.0 * Math::PI
end

#distance_between(from, to, options = {}) ⇒ Object

Returns the distance between two points. The from and to parameters are required to have lat and lng attributes. Valid options are: :units - valid values are :miles, :kms, :nms (Geokit::default_units is the default) :formula - valid values are :flat or :sphere (Geokit::default_formula is the default)



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# File 'lib/geokit/mappable.rb', line 35

def distance_between(from, to, options = {})
  from = Geokit::LatLng.normalize(from)
  to = Geokit::LatLng.normalize(to)
  return 0.0 if from == to # fixes a "zero-distance" bug
  units = options[:units] || Geokit.default_units
  formula = options[:formula] || Geokit.default_formula
  case formula
  when :sphere then distance_between_sphere(from, to, units)
  when :flat   then distance_between_flat(from, to, units)
  end
end

#distance_between_flat(from, to, units) ⇒ Object 



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# File 'lib/geokit/mappable.rb', line 56

def distance_between_flat(from, to, units)
  lat_length = units_per_latitude_degree(units) * (from.lat - to.lat)
  lng_length = units_per_longitude_degree(from.lat, units) *
               (from.lng - to.lng)
  Math.sqrt(lat_length**2 + lng_length**2)
end

#distance_between_sphere(from, to, units) ⇒ Object 



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# File 'lib/geokit/mappable.rb', line 47

def distance_between_sphere(from, to, units)
  lat_sin = Math.sin(deg2rad(from.lat)) * Math.sin(deg2rad(to.lat))
  lat_cos = Math.cos(deg2rad(from.lat)) * Math.cos(deg2rad(to.lat))
  lng_cos = Math.cos(deg2rad(to.lng) - deg2rad(from.lng))
  units_sphere_multiplier(units) * Math.acos(lat_sin + lat_cos * lng_cos)
rescue *math_error_classes
  0.0
end

#endpoint(start, heading, distance, options = {}) ⇒ Object

Given a start point, distance, and heading (in degrees), provides an endpoint. Returns a LatLng instance. Typically, the instance method will be used instead of this method.



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# File 'lib/geokit/mappable.rb', line 88

def endpoint(start, heading, distance, options = {})
  units   = options[:units] || Geokit.default_units
  ratio   = distance.to_f / units_sphere_multiplier(units)
  start   = Geokit::LatLng.normalize(start)
  lat     = deg2rad(start.lat)
  lng     = deg2rad(start.lng)
  heading = deg2rad(heading)

  sin_ratio = Math.sin(ratio)
  cos_ratio = Math.cos(ratio)
  sin_lat = Math.sin(lat)
  cos_lat = Math.cos(lat)

  end_lat = Math.asin(sin_lat * cos_ratio +
                      cos_lat * sin_ratio * Math.cos(heading))

  end_lng = lng + Math.atan2(Math.sin(heading) * sin_ratio * cos_lat,
                             cos_ratio - sin_lat * Math.sin(end_lat))

  LatLng.new(rad2deg(end_lat), rad2deg(end_lng))
end

#geocode(location, options = {}) ⇒ Object

Geocodes a location using the multi geocoder.

Raises:



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# File 'lib/geokit/mappable.rb', line 124

def geocode(location, options = {})
  res = Geocoders::MultiGeocoder.geocode(location, options)
  return res if res.success?
  raise Geokit::Geocoders::GeocodeError
end

#heading_between(from, to) ⇒ Object

Returns heading in degrees (0 is north, 90 is east, 180 is south, etc) from the first point to the second point. Typicaly, the instance methods will be used instead of this method.



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# File 'lib/geokit/mappable.rb', line 72

def heading_between(from, to)
  from = Geokit::LatLng.normalize(from)
  to = Geokit::LatLng.normalize(to)

  d_lng = deg2rad(to.lng - from.lng)
  from_lat = deg2rad(from.lat)
  to_lat = deg2rad(to.lat)
  y = Math.sin(d_lng) * Math.cos(to_lat)
  x = Math.cos(from_lat) * Math.sin(to_lat) -
      Math.sin(from_lat) * Math.cos(to_lat) * Math.cos(d_lng)
  to_heading(Math.atan2(y, x))
end

#math_error_classes ⇒ Object

Ruby 1.9 raises Math::DomainError, but it is not defined in Ruby 1.8



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# File 'lib/geokit/mappable.rb', line 64

def math_error_classes
  return [Errno::EDOM, Math::DomainError] if defined?(Math::DomainError)
  [Errno::EDOM]
end

#midpoint_between(from, to, options = {}) ⇒ Object

Returns the midpoint, given two points. Returns a LatLng. Typically, the instance method will be used instead of this method. Valid option:

:units - valid values are :miles, :kms, or :nms
(:miles is the default)



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# File 'lib/geokit/mappable.rb', line 115

def midpoint_between(from, to, options = {})
  from = Geokit::LatLng.normalize(from)

  heading = from.heading_to(to)
  distance = from.distance_to(to, options)
  from.endpoint(heading, distance / 2, options)
end

#rad2deg(rad) ⇒ Object 



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# File 'lib/geokit/mappable.rb', line 147

def rad2deg(rad)
  rad.to_f * 180.0 / Math::PI
end

#to_heading(rad) ⇒ Object 



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# File 'lib/geokit/mappable.rb', line 151

def to_heading(rad)
  (rad2deg(rad) + 360) % 360
end

#units_per_latitude_degree(units) ⇒ Object

Returns the number of units per latitude degree.



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# File 'lib/geokit/mappable.rb', line 173

def units_per_latitude_degree(units)
  PER_LATITUDE_DEGREE[units]
end

#units_per_longitude_degree(lat, units) ⇒ Object

Returns the number units per longitude degree.



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# File 'lib/geokit/mappable.rb', line 178

def units_per_longitude_degree(lat, units)
  units_sphere_multiplier(units) * Math.cos(lat * PI_DIV_RAD) * PI_DIV_RAD
end

#units_sphere_multiplier(units) ⇒ Object

Returns the multiplier used to obtain the correct distance units. TODO make more accurate by coping msi.nga.mil/MSISiteContent/StaticFiles/Calculators/degree.html



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# File 'lib/geokit/mappable.rb', line 168

def units_sphere_multiplier(units)
  EARTH_RADIUS[units]
end