Google geocoder is returning different latitude and longitude from request values

Question

I'm getting the location from a latitude and a longitude given:

getLocationFromCoords(lat, lng) {
    var geocoder = new google.maps.Geocoder();
    var latLng = new google.maps.LatLng(parseFloat(lat), parseFloat(lng));
    geocoder.geocode({
        'latLng': latLng
    }, function (results, status) {
        if (status === google.maps.GeocoderStatus.OK) {
            if (typeof results[0].geometry.location != 'undefined') {

                console.log(lat, lng);
                console.log(results[0].geometry.location.lat(), results[0].geometry.location.lng());

                // set the location
            } else {
                //...
            }
        });
    });
}

The problem is that the latitude and longitude from results[0].geometry.location differ from the values of the request. The above code displays in the console:

38.9067339 1.4205983

38.9069681 1.4205133000000387

So am I missing anything? Why aren't the same values?

Answer 1

Geocoding or Reverse Geocoding can not give exact result. If you Geocode Address to LatLong you will get most appropriate and nearest record from Google. That is normal behaviour. Also Google's official example have same behaviour. (not error or problem).

Check this fiddle ;

 function initMap() { var map = new google.maps.Map(document.getElementById('map'), { zoom: 8, center: {lat: 40.731, lng: -73.997} }); var geocoder = new google.maps.Geocoder; var infowindow = new google.maps.InfoWindow; document.getElementById('submit').addEventListener('click', function() { geocodeLatLng(geocoder, map, infowindow); }); } function geocodeLatLng(geocoder, map, infowindow) { var input = document.getElementById('latlng').value; var latlngStr = input.split(',', 2); var latlng = {lat: parseFloat(latlngStr[0]), lng: parseFloat(latlngStr[1])}; geocoder.geocode({'location': latlng}, function(results, status) { if (status === 'OK') { if (results[1]) { map.setZoom(11); var marker = new google.maps.Marker({ position: latlng, map: map }); infowindow.setContent( results[1].formatted_address + "<br />" + results[1].geometry.location ); infowindow.open(map, marker); } else { window.alert('No results found'); } } else { window.alert('Geocoder failed due to: ' + status); } }); } 

 html, body { height: 100%; margin: 0; padding: 0; } #map { height: 100%; } #floating-panel { position: absolute; top: 10px; left: 25%; z-index: 5; background-color: #fff; padding: 5px; border: 1px solid #999; text-align: center; font-family: 'Roboto','sans-serif'; line-height: 30px; padding-left: 10px; } #floating-panel { position: absolute; top: 5px; left: 50%; margin-left: -180px; width: 350px; z-index: 5; background-color: #fff; padding: 5px; border: 1px solid #999; } #latlng { width: 225px; } 

 <div id="floating-panel"> <input id="latlng" type="text" value="40.714224,-73.961452"> <input id="submit" type="button" value="Reverse Geocode"> </div> <div id="map"></div> <!-- Replace the value of the key parameter with your own API key. --> <script async defer src="https://maps.googleapis.com/maps/api/js?callback=initMap"> </script> 

Answer 2

Geocoding (matching locations to latitude-longitude pairs and vice versa) is only accurate when you search for a known address or a known place. There are databases available that provide exact information for all real addresses. And, there are services and APIs that specialize in using that kind of data. For instance, address validation services search against a list of real addresses. They parse address input and can determine if the input is a real address or not. For people who use these services (such as people who deal with shipping), exact accuracy is important with their addresses.

However, many geocoding services prefer to give a user an answer even if there isn't a perfect one - ie if there is no official data that matches the input. Google's mapping services, for instance, will give you a result even if the input isn't a real address. They use good algorithms to give you an “estimated guess” on a map. There are lots of good things about Google's services, but one of the weaknesses is some responses will not be exact.

In other cases, big public places or other named locations may match many latitude and longitude pairs, but the data that matches the name is slightly different from search input.

In your specific case, maybe Google found that your latitude and longitude input was very close to an actual landmark or place and assumed that was what you wanted. Or, the place is big (like a park) and Google's info for that park pinpoints a different spot as "the middle".

Google's results are normally close, as has already been mentioned. When you use one of these services and enter latitude and longitude, search for a corresponding place, and then convert back to latitude and longitude, it is likely that there has been a slight change.

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(Full disclosure: I work for SmartyStreets , an address validation company.)