How to Convert Google Maps API V2.0 to V3.0 - A c# overview with code snippet to handle XML Results

Asif Munir September 27, 2013

C# Code for Geocoding Requests to process XML Output:


query should contain post code with a country name.
 public static Geoloc? LocateGoogle(string query)
        {
            string url = "http://maps.google.com/maps/api/geocode/xml?address={0}&region=dk&sensor=false";
            url = String.Format(url, query);
            XmlNode coords = null;
            try
            {
                string xmlString = GetUrl(url);
                XmlDocument xd = new XmlDocument();
                xd.LoadXml(xmlString);
                XmlNamespaceManager xnm = new XmlNamespaceManager(xd.NameTable);
                //coords = xd.SelectSingleNode("/").ChildNodes[1].ChildNodes[0].ChildNodes[2].LastChild;
                coords = xd.GetElementsByTagName("location")[0];
            }
            catch { }
            Geoloc? gl = null;
            if (coords != null)
            {
                string lat = coords.ChildNodes[0].InnerXml;
                string lng = coords.ChildNodes[1].InnerXml;
                gl = new Geoloc(Convert.ToDouble(lat), Convert.ToDouble(lng));
            }
            return gl;
        }

Geocoding Requests

A Geocoding API request must be of the following form:
http://maps.googleapis.com/maps/api/geocode/output?parameters
where output may be either of the following values:
  • json (recommended) indicates output in JavaScript Object Notation (JSON)
  • xml indicates output as XML
To access the Geocoding API over HTTPS, use:
https://maps.googleapis.com/maps/api/geocode/output?parameters
HTTPS is recommended for applications that include sensitive user data, such as a user's location, in requests.
In either case, certain parameters are required while some are optional. As is standard in URLs, all parameters are separated using the ampersand (&) character. The list of parameters and their possible values are enumerated below.
Required parameters
  • address — The address that you want to geocode.
         or
    latlng — The textual latitude/longitude value for which you wish to obtain the closest, human-readable address. See Reverse Geocoding for more information.
         or
    components — A component filter for which you wish to obtain a geocode. See Component Filtering for more information. The components filter will also be accepted as an optional parameter if an address is provided.
  • sensor — Indicates whether or not the geocoding request comes from a device with a location sensor. This value must be either true or false.
Maps API for Business users must include valid client and signature parameters with their Geocoding requests. Please refer to Maps API for Business Web Servicesfor more information.
Optional parameters
  • bounds — The bounding box of the viewport within which to bias geocode results more prominently. This parameter will only influence, not fully restrict, results from the geocoder. (For more information see Viewport Biasing below.)
  • language — The language in which to return results. See the list of supported domain languages. Note that we often update supported languages so this list may not be exhaustive. If language is not supplied, the geocoder will attempt to use the native language of the domain from which the request is sent wherever possible.
  • region — The region code, specified as a ccTLD ("top-level domain") two-character value. This parameter will only influence, not fully restrict, results from the geocoder. (For more information see Region Biasing below.)
  • components — The component filters, separated by a pipe (|). Each component filter consists of a component:value pair and will fully restrict the results from the geocoder. For more information see Component Filtering, below.

Geocoding Responses

Geocoding responses are returned in the format indicates by the output flag within the URL request's path.

JSON Output Formats

In this example, the Geocoding API requests a json response for a query on "1600 Amphitheatre Parkway, Mountain View, CA":
http://maps.googleapis.com/maps/api/geocode/json?address=1600+Amphitheatre+Parkway,+Mountain+View,+CA&sensor=true_or_false
We've left the sensor parameter in this example as a variable true_or_false to emphasize that you must set this value to either true or false explicitly.
The JSON returned by this request is shown below. Note that actual JSON may contain less whitespace. You should not make assumptions about the amount or format of whitespace between requests.
{
   "results" : [
      {
         "address_components" : [
            {
               "long_name" : "1600",
               "short_name" : "1600",
               "types" : [ "street_number" ]
            },
            {
               "long_name" : "Amphitheatre Pkwy",
               "short_name" : "Amphitheatre Pkwy",
               "types" : [ "route" ]
            },
            {
               "long_name" : "Mountain View",
               "short_name" : "Mountain View",
               "types" : [ "locality", "political" ]
            },
            {
               "long_name" : "Santa Clara",
               "short_name" : "Santa Clara",
               "types" : [ "administrative_area_level_2", "political" ]
            },
            {
               "long_name" : "California",
               "short_name" : "CA",
               "types" : [ "administrative_area_level_1", "political" ]
            },
            {
               "long_name" : "United States",
               "short_name" : "US",
               "types" : [ "country", "political" ]
            },
            {
               "long_name" : "94043",
               "short_name" : "94043",
               "types" : [ "postal_code" ]
            }
         ],
         "formatted_address" : "1600 Amphitheatre Pkwy, Mountain View, CA 94043, USA",
         "geometry" : {
            "location" : {
               "lat" : 37.42291810,
               "lng" : -122.08542120
            },
            "location_type" : "ROOFTOP",
            "viewport" : {
               "northeast" : {
                  "lat" : 37.42426708029149,
                  "lng" : -122.0840722197085
               },
               "southwest" : {
                  "lat" : 37.42156911970850,
                  "lng" : -122.0867701802915
               }
            }
         },
         "types" : [ "street_address" ]
      }
   ],
   "status" : "OK"
}
Note that the JSON response contains two root elements:
  • "status" contains metadata on the request. See Status Codes below.
  • "results" contains an array of geocoded address information and geometry information.
Generally, only one entry in the "results" array is returned for address lookups, though the geocoder may return several results when address queries are ambiguous.
Note that these results generally need to be parsed if you wish to extract values from the results. Parsing JSON is relatively easy. See Parsing JSON for some recommended design patterns.

XML Output Formats

In this example, the Geocoding API requests an xml response for the identical query shown above for "1600 Amphitheatre Parkway, Mountain View, CA":
http://maps.googleapis.com/maps/api/geocode/xml?address=1600+Amphitheatre+Parkway,+Mountain+View,+CA&sensor=true_or_false
The XML returned by this request is shown below.
<GeocodeResponse>
 <status>OK</status>
 <result>
  <type>street_address</type>
  <formatted_address>1600 Amphitheatre Pkwy, Mountain View, CA 94043, USA</formatted_address>
  <address_component>
   <long_name>1600</long_name>
   <short_name>1600</short_name>
   <type>street_number</type>
  </address_component>
  <address_component>
   <long_name>Amphitheatre Pkwy</long_name>
   <short_name>Amphitheatre Pkwy</short_name>
   <type>route</type>
  </address_component>
  <address_component>
   <long_name>Mountain View</long_name>
   <short_name>Mountain View</short_name>
   <type>locality</type>
   <type>political</type>
  </address_component>
  <address_component>
   <long_name>San Jose</long_name>
   <short_name>San Jose</short_name>
   <type>administrative_area_level_3</type>
   <type>political</type>
  </address_component>
  <address_component>
   <long_name>Santa Clara</long_name>
   <short_name>Santa Clara</short_name>
   <type>administrative_area_level_2</type>
   <type>political</type>
  </address_component>
  <address_component>
   <long_name>California</long_name>
   <short_name>CA</short_name>
   <type>administrative_area_level_1</type>
   <type>political</type>
  </address_component>
  <address_component>
   <long_name>United States</long_name>
   <short_name>US</short_name>
   <type>country</type>
   <type>political</type>
  </address_component>
  <address_component>
   <long_name>94043</long_name>
   <short_name>94043</short_name>
   <type>postal_code</type>
  </address_component>
  <geometry>
   <location>
    <lat>37.4217550</lat>
    <lng>-122.0846330</lng>
   </location>
   <location_type>ROOFTOP</location_type>
   <viewport>
    <southwest>
     <lat>37.4188514</lat>
     <lng>-122.0874526</lng>
    </southwest>
    <northeast>
     <lat>37.4251466</lat>
     <lng>-122.0811574</lng>
    </northeast>
   </viewport>
  </geometry>
 </result>
</GeocodeResponse>
Note that the XML response consists of a single <GeocodeResponse> and two top-level elements:
  • <status> contains metadata on the request. See Status Codes below.
  • Zero or more <result> elements, each containing a single set of geocoded address information and geometry information.
Note that this response is considerably longer than the JSON response. For that reason, we recommend that you use json as the preferred output flag unless your service requires xml for some reason. Additionally, processing XML trees requires some care, so that you reference proper nodes and elements. See Parsing XML with XPath for some recommended design patterns for output processing.
The remainder of this documentation will use JSON syntax. In most cases, the output format does not matter for purposes of illustrating concepts or field names in the documentation. However, note the following subtle differences:
  • XML results are wrapped in a root <GeocodeResponse> element.
  • JSON denotes entries with multiple elements by plural arrays (types), while XML denotes these using multiple singular elements (<type>).
  • Blank elements are indicated through empty arrays in JSON, but by the absense of any such element in XML. A response that generates no results will return an empty results array in JSON, but no <result> elements in XML, for example.

Status Codes

The "status" field within the Geocoding response object contains the status of the request, and may contain debugging information to help you track down why Geocoding is not working. The "status" field may contain the following values:
  • "OK" indicates that no errors occurred; the address was successfully parsed and at least one geocode was returned.
  • "ZERO_RESULTS" indicates that the geocode was successful but returned no results. This may occur if the geocode was passed a non-existent address or alatlng in a remote location.
  • "OVER_QUERY_LIMIT" indicates that you are over your quota.
  • "REQUEST_DENIED" indicates that your request was denied, generally because of lack of a sensor parameter.
  • "INVALID_REQUEST" generally indicates that the query (address or latlng) is missing.
  • UNKNOWN_ERROR indicates that the request could not be processed due to a server error. The request may succeed if you try again.

Results

When the geocoder returns results, it places them within a (JSON) results array. Even if the geocoder returns no results (such as if the address doesn't exist) it still returns an empty results array. (XML responses consist of zero or more <result> elements.)
A typical result is made up of the following fields:
  • The types[] array indicates the type of the returned result. This array contains a set of zero or more tags identifying the type of feature returned in the result. For example, a geocode of "Chicago" returns "locality" which indicates that "Chicago" is a city, and also returns "political" which indicates it is a political entity.
  • formatted_address is a string containing the human-readable address of this location. Often this address is equivalent to the "postal address," which sometimes differs from country to country. (Note that some countries, such as the United Kingdom, do not allow distribution of true postal addresses due to licensing restrictions.) This address is generally composed of one or more address components. For example, the address "111 8th Avenue, New York, NY" contains separate address components for "111" (the street number, "8th Avenue" (the route), "New York" (the city) and "NY" (the US state). These address components contain additional information as noted below.
  • address_components[] is an array containing the separate address components, as explained above. Each address_component typically contains:
    • types[] is an array indicating the type of the address component.
    • long_name is the full text description or name of the address component as returned by the Geocoder.
    • short_name is an abbreviated textual name for the address component, if available. For example, an address component for the state of Alaska may have along_name of "Alaska" and a short_name of "AK" using the 2-letter postal abbreviation.
    Note that address_components[] may contain more address components than noted within the formatted_address.
  • postcode_localities[] is an array denoting all the localities contained in a postal code. This is only present when the result is a postal code that contains multiple localities.
  • geometry contains the following information:
    • location contains the geocoded latitude,longitude value. For normal address lookups, this field is typically the most important.
    • location_type stores additional data about the specified location. The following values are currently supported:
      • "ROOFTOP" indicates that the returned result is a precise geocode for which we have location information accurate down to street address precision.
      • "RANGE_INTERPOLATED" indicates that the returned result reflects an approximation (usually on a road) interpolated between two precise points (such as intersections). Interpolated results are generally returned when rooftop geocodes are unavailable for a street address.
      • "GEOMETRIC_CENTER" indicates that the returned result is the geometric center of a result such as a polyline (for example, a street) or polygon (region).
      • "APPROXIMATE" indicates that the returned result is approximate.
    • viewport contains the recommended viewport for displaying the returned result, specified as two latitude,longitude values defining the southwest andnortheast corner of the viewport bounding box. Generally the viewport is used to frame a result when displaying it to a user.
    • bounds (optionally returned) stores the bounding box which can fully contain the returned result. Note that these bounds may not match the recommended viewport. (For example, San Francisco includes the Farallon islands, which are technically part of the city, but probably should not be returned in the viewport.)
  • partial_match indicates that the geocoder did not return an exact match for the original request, though it was able to match part of the requested address. You may wish to examine the original request for misspellings and/or an incomplete address.
    Partial matches most often occur for street addresses that do not exist within the locality you pass in the request. Partial matches may also be returned when a request matches two or more locations in the same locality. For example, "21 Henr St, Bristol, UK" will return a partial match for both Henry Street and Henrietta Street. Note that if a request includes a misspelled address component, the geocoding service may suggest an alternate address. Suggestions triggered in this way will not be marked as a partial match.
As the exact format of an individual response to a Geocoding API request is not guaranteed, you should never assume that elements are in absolute positions. (In particular, the number of address_components within a Geocoding API response vary based on the address requested and can change over time.) Instead, you should parse the response and select appropriate values via expressions. See Parsing Web Service Responses for more information.

Address Component Types

The types[] array within the returned result indicates the address type. These types may also be returned within address_components[] arrays to indicate the type of the particular address component. Addresses within the geocoder may have multiple types; the types may be considered "tags". For example, many cities are tagged with the political and locality type.
The following types are supported and returned by the HTTP Geocoder:
  • street_address indicates a precise street address.
  • route indicates a named route (such as "US 101").
  • intersection indicates a major intersection, usually of two major roads.
  • political indicates a political entity. Usually, this type indicates a polygon of some civil administration.
  • country indicates the national political entity, and is typically the highest order type returned by the Geocoder.
  • administrative_area_level_1 indicates a first-order civil entity below the country level. Within the United States, these administrative levels are states. Not all nations exhibit these administrative levels.
  • administrative_area_level_2 indicates a second-order civil entity below the country level. Within the United States, these administrative levels are counties. Not all nations exhibit these administrative levels.
  • administrative_area_level_3 indicates a third-order civil entity below the country level. This type indicates a minor civil division. Not all nations exhibit these administrative levels.
  • colloquial_area indicates a commonly-used alternative name for the entity.
  • locality indicates an incorporated city or town political entity.
  • sublocality indicates a first-order civil entity below a locality. For some locations may receive one of the additional types: sublocality_level_1 through tosublocality_level_5. Each sublocality level is a civil entity. Larger numbers indicate a smaller geographic area.
  • neighborhood indicates a named neighborhood
  • premise indicates a named location, usually a building or collection of buildings with a common name
  • subpremise indicates a first-order entity below a named location, usually a singular building within a collection of buildings with a common name
  • postal_code indicates a postal code as used to address postal mail within the country.
  • natural_feature indicates a prominent natural feature.
  • airport indicates an airport.
  • park indicates a named park.
  • point_of_interest indicates a named point of interest. Typically, these "POI"s are prominent local entities that don't easily fit in another category such as "Empire State Building" or "Statue of Liberty."
An empty list of types indicates there are no known types for the particular address component, for instance Lieu-dit in France.
In addition to the above, address components may include the types below.
Note: This list is not exhaustive, and is subject to change.
  • floor indicates the floor of a building address.
  • establishment typically indicates a place that has not yet been categorized.
  • parking indicates a parking lot or parking structure.
  • post_box indicates a specific postal box.
  • postal_town indicates a grouping of geographic areas, such as locality and sublocality, used for mailing addresses in some countries.
  • room indicates the room of a building address.
  • street_number indicates the precise street number.
  • train_station and train_station indicate the location of a train or public transit stop.

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