@Override
    public Geopoint getCenter() {
        final MapPosition pos = mMap.getMapPosition();
        return new Geopoint(pos.getLatitude(), pos.getLongitude());
    }
call this instead of VTM.layers().add so that we can keep track of layers added by the tile provider
main/src/main/java/cgeo/geocaching/unifiedmap/mapsforgevtm/MapsforgeVtmFragment.java