Fundamental levelling networks and height datums at the territory of the Republic of Croatia

In the Republic of Croatia there is a long tradition going on in carrying out systematic levelling works. These works have resulted, in the period of about 120 years, with the establishment of three fundamental levelling networks of geometric levelling. These are precise levelling network of the Austro-Hungarian Monarchy, I. levelling network of high accuracy and II. levelling network of high accuracy of former Yugoslavia. These networks are the basis of height system of the Republic of Croatia, and accompanied by adequate definitions of height datums they are used even today for solving fundamental and applied geodetic tasks and scientific researches.