Google Geocoding

    地理信息最重要的信息就是地理位置，如何能快速有效的定位到我们所期望的地方，是每一个GIS系统需要认真考虑的问题，根据属性定位空间位置和选择空间位置查询属性信息，成为现在绝大多数GIS系统的基本功能。

    同样是位置查询，Geocoding的功能更贴近我们的生活，它可以将具体的地址信息转换为空间坐标点（X/Y），Reverse Geocoding则是将一个空间坐标点转换为具体的地址信息。Geocoding规则建立需要城市街道命名规范、完整，是中国城市所欠缺的，需要逐步完善。ArcGIS很早就提供了对Geocoding支持，现在Google也实现了相似的功能，包括Geocoding和Reverse Geocoding，加上Google Map/Earth，Google在逐步成为一个面向大众网络GIS基础服务中心。

    GClientGeocoder对象的getLatLng和getLocations分别实现Geocoding和Reverse Geocoding。

    Geocoding

var  map  =   new  GMap2(document.getElementById( " map_canvas " ));
var  geocoder  =   new  GClientGeocoder();
function  showAddress(address) {
    geocoder.getLatLng(
        address,
         function (point) {
             if  ( ! point) {
                alert(address  +   "  not found " );
            }  else  {
                map.setCenter(point,  13 );
                 var  marker  =   new  GMarker(point);
                map.addOverlay(marker);
                marker.openInfoWindowHtml(address);
            }
        }
    );
}

    Reverse Geocoding

var  map;
var  geocoder;
var  address;
function  initialize() {
    map  =   new  GMap2(document.getElementById( " map_canvas " ));
    map.setCenter( new  GLatLng( 40.730885 , - 73.997383 ),  15 );
    map.addControl( new  GLargeMapControl);
    GEvent.addListener(map,  " click " , getAddress);
    geocoder  =   new  GClientGeocoder();
}
function  getAddress(overlay, latlng) {
     if  (latlng  !=   null ) {
        address  =  latlng;
        geocoder.getLocations(latlng, showAddress);
    }
}
function  showAddress(response) {
    map.clearOverlays();
     if  ( ! response  ||  response.Status.code  !=   200 ) {
        alert( " Status Code: "   +  response.Status.code);
    }  else  {
        place  =  response.Placemark[ 0 ];
        point  =   new  GLatLng(place.Point.coordinates[ 1 ],place.Point.coordinates[ 0 ]);
        marker  =   new  GMarker(point);
        map.addOverlay(marker);
        marker.openInfoWindowHtml(
             ' <b>orig latlng:</b> '   +  response.name  +   ' <br/> '   +  
             ' <b>latlng:</b> '   +  place.Point.coordinates[ 0 ]  +   " , "   +  place.Point.coordinates[ 1 ]  +   ' <br> '   +  
             ' <b>Status Code:</b> '   +  response.Status.code  +   ' <br> '   +  
             ' <b>Status Request:</b> '   +  response.Status.request  +   ' <br> '   +  
             ' <b>Address:</b> '   +  place.address  +   ' <br> '   +  
             ' <b>Accuracy:</b> '   +  place.AddressDetails.Accuracy  +   ' <br> '   +  
             ' <b>Country code:</b>  '   +  place.AddressDetails.Country.CountryNameCode);
    }
}

    To access the Maps API Geocoder, send a request to http://maps.google.com/maps/geo? with the following parameters in the URI:

    q (required) — The address that you want to geocode. 
    key (required) — Your API key. 
    output (required) — The format in which the output should be generated. The options are xml, kml, csv, or (default) json. 
    ll (optional) — The {latitude,longitude} of the viewport center expressed as a comma-separated string (e.g. "ll=40.479581,-117.773438" ). This parameter only has meaning if the spn parameter is also passed to the geocoder. 
    spn (optional) — The "span" of the viewport expressed as a comma-separated string of {latitude,longitude} (e.g. "spn=11.1873,22.5" ). This parameter only has meaning if the ll parameter is also passed to the geocoder. 
    gl (optional) — The country code, specified as a ccTLD ("top-level domain") two-character value. 
    Note: The gl and spn,ll viewport parameters will only influence, not fully restrict, results from the geocoder.

    In this example, we request the geographic coordinates of Google's headquarters:
    http://maps.google.com/maps/geo?q=1600+Amphitheatre+Parkway,+Mountain+View,+CA&output=xml&key=abcdefg

本文转自Flyingis博客园博客，原文链接：http://www.cnblogs.com/flyingis/archive/2008/11/09/1329287.html，如需转载请自行联系原作者