def buildDefaultRefWCS(self):
        """ Generate a default reference WCS for this image. """
        self.default_refWCS = None
        if self.use_wcs:
            wcslist = []
            for scichip in self.chip_catalogs:
                wcslist.append(self.chip_catalogs[scichip]['wcs'])
            self.default_refWCS = utils.output_wcs(wcslist)
Generate a default reference WCS for this image.