API sometimes extremely inaccurate

 Hello! 

I'm currently developing a new web app which uses your awesome W3C geolocation api!
Although it works perfectly while in or near bigger cities, it's horribly inaccurate when using it in my hometown in Austria with about 5k inhabitants (so not that small).

I'm logged into my private WiFi network. Of course I'm NOT expecting extremely accurate results ins such small towns like mine but in my case the API places me 140 km (!!!) off my right location, which is unacceptable. 

I'm using the watchPosition() Method.
Am I doing something wrong? Or is it just that inaccurate?

best regards
Patrick