Crystal Orientation Mapping (COM) is a new state-of-the-art technique for makingspatially specific orientation measurements based on the automatic analysis ofelectron backscatter diffraction patterns. The main aim of the work reported is todemonstrate the quantitative application of COM for characterising local orientationperturbations 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 theoptimum microscope operating conditions for setting up a COM are determined bymeasuring the spatial resolution of EBSD patterns in pure Al and Ni specimens. Forthis 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 μmfor Al and Ni respectively. Secondly, to provide a visual representation of localorientation perturbations in the vicinity of a triple junction, a COM and patternquality map are presented. The “raw” orientation data extracted from the COM wasquantified using several different post-processing methods. The methodology associatedwith each is discussed and comparisons of the pattern of orientation perturbations aremade using the same “raw” data set.