Derived at 53 points in May 2009. Residuals at 58 test points within 0.2m horizontal and 2m vertical. Info source also provides a Position Vector tfm of similar accuracy. See codes 5025-26 for preferred tfms for islands of Sao Miguel and Santa Maria.
Instituto Geografico Portugues; http://www.igeo.pt
See CRS code 4664 for recommended coordinate axis representation for the human interface.