DFC
Barcelona on westerlies. Radar vectors to the ILS often leave you a shade high if ATC bring you in tight. High(ish) ground on base leg means ATC cannot offer a lower level unless you are visual with the surface. By reporting visual with the terrain beneath (and obviously maintaining safe separation from it), ATC can allow you an extra couple of feet descent, thereby allowing a nice high speed, CDA ILS to be flown.
G W-H