c# - Measure distance by longitude and lattitude -

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• calculating distance between 2 latitude , longitude geocoordinates 9 answers

first of all, i'm not sure if best way it, but...

i have amassed table of longitude , lattitude points zip codes in us. want able allow user choose zip code, select radius in miles (5, 10, 20, 40, etc...) , app list users in radius.

it doesn't need incredibly accurate, it's got close. i've been poking around looking other ways i'm stumped, , can't find example of using long/lat it.

if in c# work best. i'm not proficient @ java might able muddle through if absolutely necessary.

edit:

my coordinates this:

countrycode zipcode place   statecode   latitude    longitude          95219   stockton     ca        38.01    -121.3698          95220   acampo       ca      38.2004    -121.2186          95227   clements     ca      38.1929    -121.0811          95230   farmington   ca      37.9945    -120.7926          95231   french camp  ca       37.878    -121.2827          95234   holt         ca      37.9344    -121.4261          95236   linden       ca       38.032    -121.0493 

this question not duplicate, linked question phone.

following code generates distance between instance of wgs84point , another. distance given assuming spherical earth , not take account earth's irregular shape.

public class wgs84point {     const double maxdegreeslongitude = 180;     const double mindegreeslongitude = -180;     const double maxdegreeslatitude = 90;     const double mindegreeslatitude = -90;      readonly double _longitude;     readonly double _latitude;      public double latitude { { return _latitude; } }      public double longitude { { return _longitude; } }      public wgs84point(double longitude, double latitude)     {         if (longitude > maxdegreeslongitude || longitude < mindegreeslongitude)             throw new argumentexception("longitude");          if (latitude > maxdegreeslatitude || latitude < mindegreeslatitude)             throw new argumentexception("latitude");          _longitude = longitude;         _latitude = latitude;     }      public distance distanceto(wgs84point that)     {         if (that == null)             throw new argumentnullexception("that");          if (this == that)             return distance.zero;          var dlat = degreestoradians(latitude - that.latitude);         var dlon = degreestoradians(longitude - that.longitude);         var = math.sin(dlat / 2) * math.sin(dlat / 2) +             math.cos(degreestoradians(latitude)) *              math.cos(degreestoradians(that.latitude)) *             math.sin(dlon / 2) * math.sin(dlon / 2);         var c = 2 * math.atan2(math.sqrt(a), math.sqrt(1 - a));         var d = distance.radiusofearth.todouble() * c;         return new distance(d);     }      static double degreestoradians(double degrees)     {         return degrees * (math.pi / 180);     } }