metmon.cs

using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using Newtonsoft.Json;

namespace metmon
{
    class Program
    {
        private const string Api = "http://datapoint.metoffice.gov.uk/public/data/val/wxfcs/all/json";
        private const string Key = "01234567-89ab-cdef-fedc-ba9876543210";
        static void Main()
        {
            using (var wc = new WebClient())
            {
                var sites = JsonConvert.DeserializeObject<dynamic>(wc.DownloadString(string.Format("{0}/sitelist?key={1}", Api, Key)));
                //var sites = JsonConvert.DeserializeObject<dynamic>(File.ReadAllText(@"c:\temp\metoffice.sitelist.json"));
                var features = new {
                    type = "FeatureCollection",
                    features = ((IEnumerable<dynamic>)sites.Locations.Location).Select(x => new
                    {
                        type = "Feature",
                        geometry = new
                        {
                            type = "Point",
                            coordinates = new double?[]
                            {
                                x.longitude,
                                x.latitude,
                                x.elevation
                            }
                        },
                        properties = new
                        {
                            x.id,
                            x.name,
                            x.region,
                            x.unitaryAuthArea,
                            nationalPark = x.GetType().GetProperty("nationalPark") != null ? x.nationalPark : null
                        }
                    })};
                File.WriteAllText(@"c:\temp\metoffice.sitelist.geojson", JsonConvert.SerializeObject(features));
            }
        }
    }
}

metoffice.sitelist.geojson