Crystal Orientation Mapping (COM) is a new state-of-the-art technique for making spatially specific orientation measurements based on the automatic analysis of electron backscatter diffraction patterns. The main aim of the work reported is to demonstrate the quantitative application of COM for characterising local orientation perturbations in the vicinity of triple junctions in an Al-3wt%Mg alloy deformed 5% in tension. First, the hardware configuration of the EBSD system is described and the optimum microscope operating conditions for setting up a COM are determined by measuring the spatial resolution of EBSD patterns in pure Al and Ni specimens. For this particular investigation, an accelerating voltage of 20 kV was found to be optimum for mapping, resulting in spatial resolutions of 0.51 μm and 0.42 μm for Al and Ni respectively. Secondly, to provide a visual representation of local orientation perturbations in the vicinity of a triple junction, a COM and pattern quality map are presented. The “raw” orientation data extracted from the COM was quantified using several different post-processing methods. The methodology associated with each is discussed and comparisons of the pattern of orientation perturbations are made using the same “raw” data set.