I'm trying out Geolocation API with HTML5 and it seems the results are more accurate than it reports:
geolocation.coords.latitude
shows ~correct latitudegeolocation.coords.longitude
shows ~correct longitudegeolocation.address.street
+geolocation.address.streetNumber
even shows the correct address.
However, the geolocation.coords.accuracy
returns 18000
(meters), although the results are 1000× more accurate.
I'm not using any real positioning sensors, such as GPS, and currently testing the API on a desktop browser. I believe should there be a positioning sensor onboard, the accuracy value would be what the positioning sensor reports. But — what defines the positioning accuracy when no positioning sensors are involved? Is it merely a lucky guess by the browser? ("Better be sure than sorry?")
Is there a spec or a draft I could look into?