flipbit

Postcodes divide the United Kingdom into logical groups for addresses, averaging 15 properties per postcode.
Postcodes have rough latitude and longitude coordinates associated with them, which makes them useful for location aware applications such as tracking and social networking. Unfortunatley the Postcode Address File (PAF) is owned by the Royal Mail, who charge for access and generate revenues of £14.9m every year.

Enter the new service Ernest Marples (named after the postmaster general who invented the postcode) that aims to overcome this restriction by offering the public a postcode API free of charge. Operating in a legal grey area, they don’t host or cache the information (it is derived from undisclosed sources) but offer a public API to access it.

Of course, alternatives do exist. Numerous services offer public domain postcodes - postcodes that have been submitted by members of the public using GPS devices. The drawback of these public domain services is that they are largely incomplete, and the accuracy of each postcode is not guaranteed to be correct.

###Free The Postcode

Free the postcode operate a site that allows users to submit postcodes and their corresponding coordinates, as well as download the results collected so far (7557 at the time of writing). If you feel like adding the database, it is made even easier with the introduction of an iPhone application.

###New Popular Edition Maps

Based upon out of copyright Ordnance Survey maps, New Popular Edition Maps provide a web based interface to view the UK as it was 50 years ago. In addition to this, it is also possible to submit the location of your postcode through the web interface. This information is then available to download (43,887 postcodes at the time of writing) and use for your own purposes, as long as your not making a profit from them (see the licence)

###Locating Postboxes

Ever found yourself needing to post a letter but not know where the nearest postbox is? This is a question that Matthew Somerville’s Locating Postboxes service aims to answer. Using data derived from a freedom of information request, the service can look-up and find your nearest postbox. A full list of all the available information (20,076 complete and partial postcodes so far) is available to download.

###Accessing Public Domain Postcodes

If you want to integrate postcode information into your .NET application, retrieving and parsing the information can be a pain. Because of this I’ve written an Online UK Postcode Finder (no longer available) that supports all the main providers and provides a simple interface for your to query. The library also includes handy functions to validate and calculate the distance between two postcodes.

namespace Flipbit.Postcodes
{
    /// <summary>
    /// Postcode Library Demo Program
    /// </summary>
    public class PostcodeDemo
    {
        /// <summary>
        /// Gets or sets the ernest marples service.
        /// </summary>
        public IPostcodeService ErnestMarplesService { get; set; }

        /// <summary>
        /// Gets or sets the free the postcode service.
        /// </summary>
        public IPostcodeService FreeThePostcodeService { get; set; }

        static void Main()
        {
            var buckinghamPalace = FreeThePostcodeService.Lookup("SW1A 1AA");
            var downingStreet = ErnestMarplesService.Lookup("SW1 2AA");

            var distance = new Distance(buckinghamPalace.Coordinates, 
                                        downingStreet.Coordinates);

            Console.WriteLine("Buckingham Palace to 10 Downing St:");
            Console.WriteLine("{0} miles", distance.Miles);            
        }
    }
}