AIP AD 1.1 - 31 top of the page, refering to T-VASIS & PAPI: "A standard installation aims to provide an obstacle clearance of at least 11m above a 1.9 degree slope within the azimuth splay of 7.5 degrees either side of the runway centreline to a distance of 5nm from the runway threshold (7nm for a runway equipped with an ILS)"