84 
• side scan sonar survey (checking for possible 
obstructions between survey lines), 
• GPS survey for precise positioning of a vessel 
on WGS 84 ellipsoid, 
• conductivity, temperature and density (CTD) 
measurements for precise determination of 
sound velocity, 
• sea level monitoring with tide gauge, for 
establishing the chart datum, 
• bottom sampling, 
• sub-bottom profiling up to 30m below sea 
bottom, 
• ship's heave, pitch, roll and draft monitoring for 
precise reduction of soundings, 
• Secci disc survey of water transparency, 
• still photography of all landmarks, approach 
channels and panoramas, 
• monitoring of sea pollution, 
• monitoring of traffic and other activities on the 
sea. 
Figure 3: Hydrographic survey area 
POST PROCESSING 
All measured parameters were automatically 
recorded in a hydrographic room on board or on the 
HSL. The reduction of soundings was done later, 
partly on board and partly in Navoceano head 
quarters. Thus IGF received more then 2500 files 
with digital hydrographic data in the period between 
October 1998 and March 1999. Depths were 
surveyed with line spacing from 10m in the port of 
Koper upto 100m at open sea. 
The most important final result of hydrographic 
survey and post processing was the fair sheet - a 
sheet of paper with a great number of soundings 
(figure 4). Navoceano presented five fair sheets, 
one at scale 1 : 25 000, two at scale 1 : 7500 and 
two at a scale 1 : 5000. Experts at IGF and the 
Ministry of Transport and Communications made 
the selection of soundings for a final chart, 
according to IHO standards (Karnicnik, Radovan, 
1998c). All relevant soundings were selected, 
taking into account the importance of the area, 
flatness of the bottom and possible dangers to 
navigation. This selection was a starting point for 
the cartographic production of the first nautical 
chart.