module GeoCalc::Rhumb
Public Class Methods
Returns the bearing from this point to the supplied point along a rhumb line, in degrees
@param [GeoPoint] Destination
point (latitude, longitude) @return [Numeric] Bearing
in degrees from North
# File lib/geo_calc/calc/rhumb.rb, line 55 def self.rhumb_bearing_to base_point, point lat1 = base_point.lat.to_rad lat2 = point.lat.to_rad dlon = (point.lon - base_point.lon).to_rad dphi = Math.log(Math.tan(lat2/2+Math::PI/4) / Math.tan(lat1/2+Math::PI/4)) if dlon.abs > Math::PI dlon = dlon>0 ? -(2*Math::PI-dlon) : (2*Math::PI+dlon); end brng = Math.atan2(dlon, dphi); (brng.to_deg+360) % 360 end
Returns the destination point from this point having travelled the given distance (in km) on the given bearing along a rhumb line
@param [GeoPoint] Starting point (latitude, longitude)
@param [Number] brng: Bearing
in degrees from North @param [Number] dist: Distance
in km @returns [Array] Destination
point as an array [lat, long]
# File lib/geo_calc/calc/rhumb.rb, line 89 def self.rhumb_destination_point base_point, brng, dist d = dist / base_point.earth_radius_km # d = angular distance covered on earth's surface lat1 = base_point.lat.to_rad lon1 = base_point.lon.to_rad brng = brng.to_rad lat2 = lat1 + d*Math.cos(brng); dlat = lat2 - lat1; dphi = Math.log(Math.tan(lat2/2+Math::PI/4) / Math.tan(lat1/2+Math::PI/4)) q = begin dlat / dphi rescue Math.cos(lat1) # E-W line gives dPhi=0 end dlon = d * Math.sin(brng) / q # check for some daft bugger going past the pole if lat2.abs > Math::PI/2 lat2 = lat2>0 ? Math::PI-lat2 : -(Math::PI-lat2) end lon2 = (lon1+dlon+3*Math::PI) % (2*Math::PI) - Math::PI [lat2.to_deg, lon2.to_deg] # GeoPoint.new end
Returns the distance from this point to the supplied point, in km, travelling along a rhumb line
@param [GeoPoint] Start point with (latitude, longitude) @param [GeoPoint] Destination
point (latitude, longitude) @return [Numeric] Distance
in km between start and destination point
# File lib/geo_calc/calc/rhumb.rb, line 19 def self.rhumb_distance_to base_point, point lat1 = base_point.lat.to_rad lat2 = point.lat.to_rad dlat = (point.lat - base_point.lat).to_rad dlon = (point.lon - base_point.lon).abs.to_rad dphi = Math.log(Math.tan(lat2/2 + Math::PI/4) / Math.tan(lat1/2 + Math::PI/4)) q = begin dlat / dphi rescue Math.cos(lat1) # E-W line gives dPhi=0 end # if dlon over 180° take shorter rhumb across 180° meridian: dlon = 2*Math::PI - dlon if (dlon > Math::PI) dist = Math.sqrt(dlat*dlat + q*q*dlon*dlon) * base_point.earth_radius_km; dist.round(4) # 4 sig figures reflects typical 0.3% accuracy of spherical model end
Public Instance Methods
Returns the bearing from this point to the supplied point along a rhumb line, in degrees
@param [GeoPoint] Destination
point (latitude, longitude) @return [Numeric] Bearing
in degrees from North
# File lib/geo_calc/calc/rhumb.rb, line 47 def rhumb_bearing_to point GeoCalc::Rhumb.rhumb_bearing_to self, point end
Returns the destination point from this point having travelled the given distance (in km) on the given bearing along a rhumb line
@param [Number] brng: Bearing
in degrees from North @param [Number] dist: Distance
in km @returns [Array] Destination
point as an array [lat, long]
# File lib/geo_calc/calc/rhumb.rb, line 77 def rhumb_destination_point brng, dist GeoCalc::Rhumb.rhumb_destination_point self, brng, dist end
Returns the distance from this point to the supplied point, in km, travelling along a rhumb line
see(#williams.best.vwh.net/avform.htm#Rhumb)
@param [GeoPoint] Destination
point latitude and longitude of @return [Numeric] Distance
in km between start and destination point
# File lib/geo_calc/calc/rhumb.rb, line 9 def rhumb_distance_to point GeoCalc::Rhumb.rhumb_distance_to self, point end