def _panoids_url(lat, lon):
    """
    Builds the URL of the script on Google's servers that returns the closest
    panoramas (ids) to a give GPS coordinate.
    """
    url = "https://maps.googleapis.com/maps/api/js/GeoPhotoService.SingleImageSearch?pb=!1m5!1sapiv3!5sUS!11m2!1m1!1b0!2m4!1m2!3d{0:}!4d{1:}!2d50!3m10!2m2!1sen!2sGB!9m1!1e2!11m4!1m3!1e2!2b1!3e2!4m10!1e1!1e2!1e3!1e4!1e8!1e6!5m1!1e2!6m1!1e2&callback=_xdc_._v2mub5"
    return url.format(lat, lon)