public static void deleteOfflineMapSources() {
        final Iterator<Map.Entry<String, MapSource>> it = mapSources.entrySet().iterator();
        while (it.hasNext()) {
            final MapSource mapSource = it.next().getValue();
            if (mapSource instanceof MapsforgeMapProvider.OfflineMapSource || mapSource instanceof MapsforgeMapProvider.OfflineMultiMapSource) {
                it.remove();
            }
        }
    }
remove offline map sources after changes of the settings
main/src/main/java/cgeo/geocaching/maps/MapProviderFactory.java