Example of the analysis of a diffraction image obtained at a surface pressure of 10 mN m−1. The lower and upper Bragg peaks are the 02 and 11 peaks indexed in a rectangular centred cell, respectively. (a) Original image with the image dimensions and the size of the beam footprint projection (white stroke). (b) Reconstructed scattering curve I(Qz). (c) Reconstructed scattering curve I(Qxy). The upper and lower curves are the integrated cut through the 11 and 02 peaks, respectively.