Question

How do I find closest airport using longitude and latitude ?

Any specific web services and any database to achieve ?

Answer 1

1. You need a dataset with fields for the airport`s latitude and
   longitude
2. Use the calculation for Great-Circle distance (GCD) as outlined on the page linked below

Wikipedia article on GCD

Please provide example code/specify the language if you would like further and more specific help

CODE:

Taken from another webpage (now defunct, used waybackmachine)

using System;  
namespace HaversineFormula  
{  
    /// <summary>  
    /// The distance type to return the results in.  
    /// </summary>  
    public enum DistanceType { Miles, Kilometers };  
    /// <summary>  
    /// Specifies a Latitude / Longitude point.  
    /// </summary>  
    public struct Position  
    {  
        public double Latitude;  
        public double Longitude;  
    }  
    class Haversine  
    {  
        /// <summary>  
        /// Returns the distance in miles or kilometers of any two  
        /// latitude / longitude points.  
        /// </summary>  
        /// <param name=”pos1″></param>  
        /// <param name=”pos2″></param>  
        /// <param name=”type”></param>  
        /// <returns></returns>  
        public double Distance(Position pos1, Position pos2, DistanceType type)  
        {  
            double R = (type == DistanceType.Miles) ? 3960 : 6371;  
            double dLat = this.toRadian(pos2.Latitude - pos1.Latitude);  
            double dLon = this.toRadian(pos2.Longitude - pos1.Longitude);  
            double a = Math.Sin(dLat / 2) * Math.Sin(dLat / 2) +  
                Math.Cos(this.toRadian(pos1.Latitude)) * Math.Cos(this.toRadian(pos2.Latitude)) *  
                Math.Sin(dLon / 2) * Math.Sin(dLon / 2);  
            double c = 2 * Math.Asin(Math.Min(1, Math.Sqrt(a)));  
            double d = R * c;  
            return d;  
        }  
        /// <summary>  
        /// Convert to Radians.  
        /// </summary>  
        /// <param name="val"></param>  
        /// <returns></returns>  
        private double toRadian(double val)  
        {  
            return (Math.PI / 180) * val;  
        }  
    }  
}  

Pseudocode:

This pseudocode should give you the answer you are looking for. I didn’t test this and the C# will probably have syntactic errors but the gist of it should be clear.

/* Set parameters */
Position currentPosition = new Position();
Position airportPosition = new Position();
Double minDistance = Double.MaxValue;
String closestAirportName = "UNKNOWN";
Haversine hv = new Haversine();

/* Set current position, remains fixed throughout */
currentPosition.Latitude = 0.000;
currentPosition.Longitude = 0.000; 

/* Compare distance to each airport with current location
* and save results if this is the closest airport so far*/
Foreach (airport in airports) {
    airportPosition = new Position(airport.Lat, airport.Lon);
    Double distanceToAirport = hv.Distance(currentPosition, airportPosition, DistanceType.Kilometers)

    if (distanceToAirport < minDistance) {
        minDistance = distanceToAirport
        closestAirportName = airport.Name
    }
}