The Hydrographic Service is one of the most important national bodies responsible for the safety of navigation. The Hydrographic Service is under the direction of the Head Department of Navigation and Oceanography. The principle functions of the HDNO are: - oceans and seas explorations; - publishing and updating of Nautical Charts and Sailing Directions; - development of aids to navigation system to provide safety of navigation. Nautical Charts and Sailing Directions published by the HDNO are listed in the Catalogues of Chart and Nautical Publications. This Catalogue comprises 6500 Chart of conventional form, more than 250 Electronic Carts in S57 and over 300 Nautical Publications covering the whole World Ocean. The Hydrographic Service of the Navy provides the operation of over 6000 aids to navigation objects.