A detailed description of the reliability of the nautical chart can be found in the publication "Behind the Nautical Chart".
GST endeavours to ensure, that nautical charts and publications are continually up-to-date and quality assured. Despite this fact, the navigator must know that the underlying data is not always complete and up-to-date or positioned in accordance with modern positioning systems.
Potential errors in nautical charts
The contents in the nautical chart can be erroneous for different reasons. Some of the reasons are listed here:
1. The depth information is incomplete due to old time's survey methods.
2. The depth information has changed due to bottom erosion and sand movement
3. Floating buoys have moved out of position
4. Building and construction close to harbours and bridges has been commenced.
When navigating in confined waters, points 1 and 2 must be taken into serious consideration.
Points 3 and 4 are mentioned in "Notice to Mariners" and navigational warnings broadcasted by VHF radio, NAVTEX or satellite. It is the responsibility of the navigator to update his navigational planning in accordance with these warnings.
The navigator must at all times evaluate and decide on the reliability of the information available, at any time, to ensure a safe passage.