Working Committee of the Surveying Authorities of the Laender of the Federal Republic of Germany (AdV): In Germany, the Länder assume responsibility for official surveying and mapping. Within AdV, the competent authorities of the Laender and three Federal Ministries co-operate to jointly address technical issues of strategic importance. Their services include: spatial reference data in the Authoritative Control Point Information System (AFIS®) with terrestrial control points; satellite positioning service SAPOS®; Authoritative Topographic-Cartographic Information System (ATKIS®) using landscape and terrain models; official topographic maps and aerial images; nation-wide digital proof of buildings and ca. 64 million land parcels in the official real estate cadastre to secure ownership rights in the land register  (authoritative real estate cadastre information system ALKIS®); integration of cadastre and topographic survey in one geospatial reference data system.