Observed properties of the different structure types identified in Sect. 3. These plots show the distributions of angular sizes, number of associated spine points and shapes of the elongated structures, filaments, networks of filaments and complexes, which are shown as filled green, magenta, blue and red circles, respectively. For clarity we have excluded the marginally resolved structures as there is significant overlap with the elongated structures. The horizontal dashed line shown in the upper panel indicates the threshold of thirty pixels required for inclusion in the catalogue while the diagonal dashed line shown in the lower panel shows the line of equality where the semi-major and semi-minor axes are equal.