A few years ago, when developing elastic properties software, we recognized the same problem with the rotation around the normal direction. We have a Tescan VEGA II, running OIM. When digging around and talking to TSL, we found notes about this back to at least 2009 (Analysis of EBSD Data (L17) 27-750, Fall 2009, Texture, Microstructure & Anisotropy; B. El-Dasher, A.D. Rollett, G.S. Rohrer, P.N. Kalu).
The issues arise both in the Euler angles and in the plots. Also, the Oxford and EDAX-TSL frames are different - they are 90˚ off from each other. In our case, the SEM-EBSD system uses requires us to rotate 90 degrees to get to the sample reference frame. For other systems, it could be, as Rüdiger notes, 180, -90, or 0. This rotation is not a problem when working with the OIM (or HKL) software, but matters if you are writing your own code or directly comparing Euler angles between systems. For the plots, you also have to check whether the geographic top of the plot matches the top of the scanned image.
We put together a short note associated with our elasticity/seismic velocity toolbox (http://umaine.edu/mecheng/faculty-and-staff/senthil-vel/software/ESP_Toolbox/), but as that language is a bit related to the software itself, we modified the wording and have posted the updated version here: http://umaine.edu/earthclimate/?p=5183. This also includes a simple way to determine the reference frame. Based on what I saw in Rüdiger's document, we are in full agreement.
As a final note, we found out that Oxford and EDAX-TSL define the a axes differently for hexagonal symmetry. This was apparently known, but not widely disseminated. OIM defines Cartesian x along a1, whereas HKL defines x along [1,0,-1,0]. This results in a 30˚ difference if you look at the values of the Euler angles for the same true orientation.
Chris Gerbi, Scott Johnson, Senthil Vel, Won Joon Song, Alden Cook
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Christopher Gerbi
Associate Professor - Mineralogy/Rheology
School of Earth and Climate Sciences
5790 Bryand Global Sciences Center
University of Maine, Orono, ME 04469-5790
USA
Tel +1 207-581-2153
FAX +1 207-581-2202
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http://umaine.edu/earthclimate
Center for Research in STEM Education
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