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Posted 9 Jan 2012

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Google Directions API Polyline Points Decoder in C#

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9 Jan 2012CPOL
Google Directions API Polyline Points Decoder in C#
I have an algorithm for Google Directions API Polyline Points Decoder in C#. It may save you some development time.

Assuming that you have collected encoded point string from the Google Direction API Call.

C#
private List<Location> DecodePolylinePoints(string encodedPoints) 
            {
                if (encodedPoints == null || encodedPoints == "") return null;
                List<Location> poly = new List<Location>();
                char[] polylinechars = encodedPoints.ToCharArray();
                int index = 0;

                int currentLat = 0;
                int currentLng = 0;
                int next5bits;
                int sum;
                int shifter;
               
                try
                {
                    while (index < polylinechars.Length)
                    {
                        // calculate next latitude
                        sum = 0;
                        shifter = 0;
                        do
                        {
                            next5bits = (int)polylinechars[index++] - 63;
                            sum |= (next5bits & 31) << shifter;
                            shifter += 5;
                        } while (next5bits >= 32 && index < polylinechars.Length);

                        if (index >= polylinechars.Length)
                            break;

                        currentLat += (sum & 1) == 1 ? ~(sum >> 1) : (sum >> 1);

                        //calculate next longitude
                        sum = 0;
                        shifter = 0;
                        do
                        {
                            next5bits = (int)polylinechars[index++] - 63;
                            sum |= (next5bits & 31) << shifter;
                            shifter += 5;
                        } while (next5bits >= 32 && index < polylinechars.Length);

                        if (index >= polylinechars.Length && next5bits >= 32)
                            break;

                        currentLng += (sum & 1) == 1 ? ~(sum >> 1) : (sum >> 1);
                        Location p = new Location();
                        p.Latitude = Convert.ToDouble(currentLat) / 100000.0;
                        p.Longitude = Convert.ToDouble(currentLng) / 100000.0;
                        poly.Add(p);
                    } 
                }
                catch (Exception ex)
                {
                    // logo it
                }
                return poly;
           }


Here Location is simply a class with Latitude and Longitude attributes.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

saboor awan
Software Developer (Senior)
Pakistan Pakistan
Expertise on Enterprise solutions, Mobile Apps & Services based applications on .NET platform. As Sr. Software Engineer, I have worked on variety of technologies like ASP.NET MVC, MS Windows Phone 7, WCF, and MS SharePoint 2010, MS Dynamics CRM.

Comments and Discussions

 
GeneralThanks, saves me some coding time. Pin
toy4fun9-Feb-14 5:57
Membertoy4fun9-Feb-14 5:57 

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