anchor.diff:      B = rstar_geometry:point2d(47.276, 120.576, undefined),
       ?assertEqual(17045.480008358903, distance(A, B)).
   
  +latitudinal_width_test() ->
  +    ?assertEqual(110574, round(latitudinal_width(0))),
  +    ?assertEqual(110649, round(latitudinal_width(15))),
  +    ?assertEqual(111132, round(latitudinal_width(45))),
  +    ?assertEqual(111412, round(latitudinal_width(60))),
  +    ?assertEqual(111694, round(latitudinal_width(90))).
  +
   -endif.
  
positive.code: %
  %%%
  -module(teles_geo_query).
  -export([query_within/2, query_around/3, query_nearest/3, distance/2]).
  -include_lib("rstar/include/rstar.hrl").
  
  -ifdef(TEST).
  
negative.code:     DistanceAngle * ?RADIUS_METERS.
  
  
  % Returns the width of a latitudinal degree
  % in meters for the given Latitude
  latitudinal_width(Lat) ->
      LatRad = Lat * ?DEGREES_TO_RAD,
      111132.954 - 559.822 * math:cos(2.0 * LatRad) + 1.175 * math:cos(4.0 * LatRad).
  
  
  -ifdef(TEST).
  
  distance_test() ->
  