Geocoding is the process of converting addresses into geographic coordinates (latitudes and longitudes). These coordinates can be used to place markers on a map. The Google Geocoding API is a direct way to access these services via an HTTP (HTTPS is recommended if you are dealing with sensitive data) request. This HTTP request must be of the following form:
"http://maps.googleapis.com/maps/api/geocode/output?parameters"
Output may be either json or xml (In Google Geocoding v2 they allowed csv also, but they have removed it in v3). Required parameters are 'address' (address that you want to geocode) and 'sensor' (indicates whether or not the request comes from a device with a location sensor).
XML output:
I wrote a simple code to send a API Request and retrieve the XML file and parse it and get the latitude/longitude values. The Send backed XML contains two important elements.
1.) <status> - describe the status of the result-whether it's success or not.
2.) <result> - contains informations of the address including latitude/longitude values.
c# code:
string location = "1600+Amphitheatre+Parkway,+Mountain+View,+CA";
float[] position =new float[2];
position = getLatLongForAddress(location);
System.Diagnostics.Debug.Write("Lattitude:"+position[0]+"Location:"+position[1]);
public float[] GetLatLongForAddress(string location)
{
string result = string.Format("http://maps.googleapis.com/maps/api/geocode/xml?address={0}&sensor=true", location);
var doc = XDocument.Load(result);
string status = doc.Element("GeocodeResponse").Element("status").Value;
//no errors occurred; the address was successfully parsed and at least one
geocode was returned.
if(status.Equals("OK"))
{
var point = doc.Element("GeocodeResponse").Element("result").
Element("geometry").Element("location");
string lat = point.Element("lat").Value;
string lng = point.Element("lng").Value;
latLong[0] = (float)Convert.ToDouble(lat);
latLong[1] = (float)Convert.ToDouble(lng);
}
else if (status.Equals("ZERO_RESULTS"))
{
//geocode was successful but returned no results
throw new ApplicationException("No maps found for this address");
}
else if (status.Equals("REQUEST_DENIED"))
{
//request was denied
throw new ApplicationException("Request Denied");
}
else if (status.Equals("INVALID_REQUEST"))
{
//address is missing
throw new ApplicationException("Address not found");
}
else if (status.Equals("UNKNOWN_ERROR"))
{
//the request could not be processed due to a server error
//throw new ApplicationException("Unknown Error. Try agian.");
GetLatLongForAddress(location);
}
return latLong;
}
Similarly you can get the json output and get the latitude/longitude values.
If you wan't learn more details about Google Geocoding API, have a peek at their documentation.
"https://developers.google.com/maps/documentation/geocoding"
