[wrong] How to move a distance in meters away from a point in Ruby using RGeo
WARNING: This post is ancient and wrong.
Here’s a method that lets you move/offset/translate a certain distance (in meters) away from a point expressed in longitude and latitude:
a = move_point(-72.4861, 44.1853, 0, 0) # POINT (-72.4861 44.18529999999999)
b = move_point(-72.4861, 44.1853, 100, 0) # POINT (-72.48520168471588 44.18529999999999)
c = move_point(-72.4861, 44.1853, 0, 100) # POINT (-72.4861 44.18594416889434)
puts a.distance(b)
puts a.distance(c)This gives you:
99.99999999906868
99.99999999906868It uses the RGeo library. Note the argument order is longitude, latitude!
require 'rgeo'
def move_point(lon, lat, x_offset_meters, y_offset_meters)
wgs84 = RGeo::Geographic.simple_mercator_factory.point(lon, lat)
wgs84_factory = wgs84.factory
webmercator = wgs84_factory.project wgs84
webmercator_factory = webmercator.factory
webmercator_moved = webmercator_factory.point(webmercator.x+x_offset_meters, webmercator.y+y_offset_meters)
wgs84_factory.unproject webmercator_moved
end
Seamus Abshere
Seamus Abshere's blog about programming
seamus@abshere.net
