I've just committed a bug fix to Subversion for a bug in GeomGridField.toPoint() where the Y axis was erroneously inverted. I should put out a maintenance release for GeoMason within a few days that includes this patch.
Alas, I even had comments in the code where I *say* that the Y axis needed to be flipped when going from real world to MASON raster coordinates. I must've undone it without realizing it sometime over the last couple years. Mea culpa!
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