public static Set<String> getHideTileproviders() {
        final Set<String> empty = Collections.emptySet();
        if (sharedPrefs == null) {
            return empty;
        }
        return sharedPrefs.getStringSet(getKey(R.string.pref_tileprovider_hidden), empty);
    }
@return zoom used for the map of a single cache
main/src/main/java/cgeo/geocaching/settings/Settings.java