Return cleaned fields as a dict, determine which geom takes
        precedence.

def clean(self):
        """Return cleaned fields as a dict, determine which geom takes
        precedence.
        """
        data = super(RasterQueryForm, self).clean()
        geom = data.pop('upload', None) or data.pop('bbox', None)
        if geom:
            data['g'] = geom
        return data