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Distance between locations, given their names
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loc1_name = 'Chicago' # => "Chicago" | |
loc2_name = 'Houston' # => "Houston" | |
# Get the lib with `gem install geocoder` | |
# it ultimately calls out to this API: http://maps.googleapis.com/maps/api/geocode/json?address=Chicago&language=en&sensor=false | |
require 'geocoder' # => true | |
include Math # => Object | |
def radians(n) | |
n * PI / 180 # => 0.7309109668442155, -1.5294285014482003, 0.5194174327134308, -1.664517065837707 | |
end # => :radians | |
alias √ sqrt | |
loc1 = Geocoder.search(loc1_name)[0] # => #<Geocoder::Result::Google:0x007fad839c5d50 @data={"address_components"=>[{"long_name"=>"Chicago", "short_name"=>"Chicago", "types"=>["locality", "political"]}, {"long_name"=>"Cook County", "short_name"=>"Cook County", "types"=>["administrative_area_level_2", "political"]}, {"long_name"=>"Illinois", "short_name"=>"IL", "types"=>["administrative_area_level_1", "political"]}, {"long_name"=>"United States", "short_name"=>"US", "types"=>["country", "political"]}], "formatted_address"=>"Chicago, IL, USA", "geometry"=>{"bounds"=>{"northeast"=>{"lat"=>42.023131, "lng"=>-87.52366099999999}, "southwest"=>{"lat"=>41.6443349, "lng"=>-87.9402669}}, "location"=>{"lat"=>41.8781136, "lng"=>-87.6297982}, "location_type"=>"APPROXIMATE", "viewport"=>{"northeast"=>{"lat"=>42.023131, "lng"=>-87.52404399999999}, "southwest"=>{"lat"=>41.6443349, "lng"=>-87.9402669}}}, "place_id"=>"ChIJ7cv00DwsDogRAMDACa2m4K8", "types"=>["locality", "political"]}, @cache_hit=nil> | |
lat1 = radians loc1.latitude # => 0.7309109668442155 | |
lon1 = radians loc1.longitude # => -1.5294285014482003 | |
loc2 = Geocoder.search(loc2_name)[0] # => #<Geocoder::Result::Google:0x007fad839edf08 @data={"address_components"=>[{"long_name"=>"Houston", "short_name"=>"Houston", "types"=>["locality", "political"]}, {"long_name"=>"Harris County", "short_name"=>"Harris County", "types"=>["administrative_area_level_2", "political"]}, {"long_name"=>"Texas", "short_name"=>"TX", "types"=>["administrative_area_level_1", "political"]}, {"long_name"=>"United States", "short_name"=>"US", "types"=>["country", "political"]}], "formatted_address"=>"Houston, TX, USA", "geometry"=>{"bounds"=>{"northeast"=>{"lat"=>30.1107319, "lng"=>-95.014496}, "southwest"=>{"lat"=>29.523624, "lng"=>-95.78808690000001}}, "location"=>{"lat"=>29.7604267, "lng"=>-95.3698028}, "location_type"=>"APPROXIMATE", "viewport"=>{"northeast"=>{"lat"=>30.1107319, "lng"=>-95.014496}, "southwest"=>{"lat"=>29.523624, "lng"=>-95.78808690000001}}}, "place_id"=>"ChIJAYWNSLS4QIYROwVl894CDco", "types"=>["locality", "political"]}, @cache_hit=nil> | |
lat2 = radians loc2.latitude # => 0.5194174327134308 | |
lon2 = radians loc2.longitude # => -1.664517065837707 | |
# "haversine" formula, found @ http://www.movable-type.co.uk/scripts/latlong.html | |
∆lat = lat1 - lat2 # => 0.21149353413078475 | |
∆lon = lon1 - lon2 # => 0.13508856438950678 | |
a = sin(∆lat/2)**2 + cos(lat1) * cos(lat2) * (sin(∆lon/2)**2) # => 0.014085141202494494 | |
c = 2 * atan2(√(a), √(1-a)) # => 0.23792244890858025 | |
r = 3_959 # radius of the earth in miles | |
# Expected: 941 miles (based on https://www.timeanddate.com/worldclock/distances.html?n=104) | |
distance = r * c # => 941.9349752290692 |
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