Charts General

Question 1

What is a nautical chart

Answer 1

A nautical chart is a special-purpose chart or book, or specially compiled data base from which such a chart or book is derived, that is officially published by or under the authority of a governmental institution and designed to meet the requirement of maritime navigation. This means that charts distributed by private companies may not be considered official nautical charts

Question 2

What is the depth reference level?

Answer 2

The depth ref level on chart is choosen so that the sailor always knows the minimum depth he will have at a certain location. Older charts use the mean spring tide low water mark (MLLWS) as a reference which is the average of the level of the two low waters on spring tide day. Modern Maps use the LAT level, which is calculated from the tide generating force due to the gravitational of the moon and sun and is always lower than the MLLWS

Question 3

Indicate a height on the map

Answer 3

A high water level is used as a reference in order to have a good indication of the minimum clearance between an obstacle and the water level. The mean high water spring (MHWS) is generally used

Question 4

Content of a nautical chart include

Answer 4

1- shoreline
2- topographic features
3- aids to navigation
4- water depth
5- hazards to navigation (wrecks)
6- nature of the seabed
7- other navigational information
8- depth contour
9- building
10- place with tidal info
11- drying height