Bing Maps Elevation Service for Windows 8/RT

SharpGIS.Bing.ElevationServiceClient.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Json;
using System.Text;
using System.Threading.Tasks;
using Windows.Foundation;

namespace SharpGIS.Bing
{
  public class ElevationServiceClient
	{
		//Service documentation:
		//http://msdn.microsoft.com/en-us/library/jj158961.aspx

		private string m_bingMapsKey;

		/// <summary>
		/// Initializes a new instance of the <see cref="ElevationServiceClient" /> class.
		/// </summary>
		/// <param name="bingMapsKey">The bing maps key.</param>
		public ElevationServiceClient(string bingMapsKey)
		{
			m_bingMapsKey = bingMapsKey;
		}

		/// <summary>
		/// Get elevations for latitude and longitude coordinates.
		/// </summary>
		/// <param name="points">The points where X = Longitude, and Y = latitude.</param>
		/// <param name="model">The height model used in results (default: Sea Level).</param>
		/// <returns>Elevation data</returns>
		public async Task<ElevationListResult> GetElevations(IEnumerable<Point> points, ElevationModel model = ElevationModel.Sealevel)
		{
			string svc = "http://dev.virtualearth.net/REST/v1/Elevation/List";
			int count = points.Count();
			var pntString = EncodePoints(points);
			var client = new HttpClient(new HttpClientHandler()
			{
				AutomaticDecompression = DecompressionMethods.Deflate | DecompressionMethods.GZip
			});
			HttpResponseMessage response;
			if (count < 400) //use GET
			{
				string url = string.Format("{0}?points={1}&key={2}&hts={3}", svc, pntString, m_bingMapsKey, model == ElevationModel.Sealevel ? "sealevel" : "ellipsoid");
				response = await client.GetAsync(url).ConfigureAwait(false);
			}
			else //Recommended to use POST when point count > 400
			{
				var content = new System.Net.Http.StringContent(
					string.Format("points={0}&hts={1}", pntString, model == ElevationModel.Sealevel ? "sealevel" : "ellipsoid" ));
				response = await client.PostAsync("http://dev.virtualearth.net/REST/v1/Elevation/List?key="+ m_bingMapsKey, content).ConfigureAwait(false);
			}
			var stream = await response.Content.ReadAsStreamAsync().ConfigureAwait(false);
			DataContractJsonSerializer s = new DataContractJsonSerializer(typeof(ElevationListResult));
			return s.ReadObject(stream) as ElevationListResult;
		}

		private static string EncodePoints(IEnumerable<Point> points)
		{
			int latitude = 0;
			int longitude = 0;
			StringBuilder result = new StringBuilder();

			foreach (var point in points)
			{

				// step 2
				var newLatitude = (int)Math.Round(point.Y * 100000);
				var newLongitude = (int)Math.Round(point.X * 100000);

				// step 3
				long dy = newLatitude - latitude;
				long dx = newLongitude - longitude;
				latitude = newLatitude;
				longitude = newLongitude;

				// step 4 and 5
				dy = (dy << 1) ^ (dy >> 31);
				dx = (dx << 1) ^ (dx >> 31);

				// step 6
				var index = ((dy + dx) * (dy + dx + 1) / 2) + dy;

				while (index > 0)
				{

					// step 7
					var rem = (int)(index & 31);
					index = (index - rem) / 32;

					// step 8
					if (index > 0) rem += 32;

					// step 9
					result.Append("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_-"[rem]);
				}
			}

			// step 10
			return result.ToString();
		}
	}

	[DataContract]
	public class ElevationListResult
	{
		[DataMember(Name = "authenticationResultCode")]
		public string AuthenticationResultCode { get; set; }
		[DataMember(Name = "brandLogoUri")]
		public Uri BrandLogoUri { get; set; }
		[DataMember(Name = "copyright")]
		public string Copyright { get; set; }
		[DataMember(Name = "resourceSets")]
		public ResourceSet[] ResourceSets { get; set; }
		[DataMember(Name = "statusCode")]
		public int StatusCode { get; set; }
		[DataMember(Name = "statusDescription")]
		public string StatusDescription { get; set; }
	}

	[DataContract]
	public class ResourceSet
	{
		[DataMember(Name = "estimatedTotal")]
		public int EstimatedTotal { get; set; }
		[DataMember(Name = "resources")]
		public Resource[] Resources { get; set; }
		[DataMember(Name = "zoomLevel")]
		public int ZoomLevel { get; set; }
	}

	[DataContract(Namespace = "http://schemas.microsoft.com/search/local/ws/rest/v1", Name = "ElevationData")]
	public class Resource
	{
		/// <summary>
		/// Elevations in meters
		/// </summary>
		[DataMember(Name = "elevations")]
		public int[] Elevations { get; set; }
		[DataMember(Name = "zoomLevel")]
		public int ZoomLevel { get; set; }
	}

	public enum ElevationModel
	{
		/// <summary>
		/// Use the geoid Earth model (EGM2008 2.5’).
		/// </summary>
		Sealevel,
		/// <summary>
		/// Use the ellipsoid Earth model (WGS84)
		/// </summary>
		Ellipsoid
	}
}