Comparison of the elliptical model to the polarization angle variations in Sh 2–27. Left: nπ-ambiguity corrected polarization angle variations along 1D image slices. Right: colour-coded lines show the data taken from the polarization angle map. A slice of the data in the xy-plane is considered, passing through l = 6° for χ(x) and b = 23° for χ(y), where (l, b) = (6°, 23°) is the centre of the ellipse.