I have to echo James in saying how remarkable it is than anything I ever did worked at all! I'm growing more and more certain that I've been double-correcting rotation for the past 2 months, and my maps don't look all that bad! .. image:: http://4.bp.blogspot.com/_lsgW26mWZnU/SMW4oOPcLaI/AAAAAAAADXw/1ARG8iyVXDQ/s400/070717_o15_rotations.png Image caption: Top left - both PA and rotang Top right - neither Bottom left - rotang only Bottom right - PA only I'm running the same sort of comparison on all of the GC and L=24 data. Check out /scratch/adam_work/ROT_TEST for the results. I'll be updating this when I've completed that analysis. Update 6:35 PM: !@#$, etc. New problem child: .. image:: http://1.bp.blogspot.com/_lsgW26mWZnU/SMXFUjLjRGI/AAAAAAAADX4/aynvuycRzGM/s400/060603_o16_rotations.png Image caption (same as above, luckily): Top left - both PA and rotang Top right - neither Bottom left - rotang only Bottom right - PA only So, can anyone tell me which one of THESE is right? Because I can't. Top left is 'correct' except that it's not. Update 7:10 PM: I compared adding/subtracting PA and RA, and I can say this: subtracting PA never works. Adding/subtracting RA works variably. I think I'm done testing parameter space. I haven't had very good luck doing parameter space tests in the past; it usually is more beneficial to take a step back and try to think through the problem. Update 7:30 PM: Fixed. Much as this looks like a short-lived, easily solved problem, it was one of the most subtle and insidious errors I've made. I got extremely lucky that plotting PA and ROTANGLE happened to spark off warning sirens in my mind about the positioning of the variable names. I wouldn't normally look for that.