Distance between locations, given their names

location_distance.rb

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

Lacey ain't no alpha

Thank you

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