Nautical charts are the main tool which you need for sailing. They usually include depth measurements, tides, offshore wrecks, and other hazards to navigation, as well as a selection of points on the earth’s surface to give positions at different time intervals. These charts are generally published by governments or private companies
The following are some ways in which you can understand whether these charts are any good
1) Not all countries that produce nautical charts publish them in English. You cannot find these publications in English if they originate from Russia or China for instance. Instead, if you want to check a nautical chart in detail in English, you must visit a reputable agency such as the American Bureau of Shipping.
2) Nautical charts are not consistent, because different companies issue them; the quality of printing and production vary from country to country, and there exist discrepancies between publications issued by one agency and those issued by the same agency. There may even be significant differences between nautical charts issued by different agencies in the same country. Hence it is essential that none of these aspects is ignored while we try to establish their usefulness.
3) Nautical charts include navigational hazards such as shoals and buoys, but they do not include marks like lighthouses and other warning signs. This is because these features are intended for operation by personnel onshore.
4) The contour of the sea surface is represented by various symbols in nautical charts. These symbols are subtle enough to indicate shallow areas but they are not so universal in their meaning that they may be interpreted in exactly the same way when seen by different navigators.
5) Nautical charts do not show all the geographical features that can affect navigation. They may show small islands, but large ones might be omitted altogether, especially if these islands are not considered to be relevant to navigation.
6) Nautical charts do not contain information about external hazards such as weather, tides, and currents.
7) Nautical charts may be inadequate in terms of accuracy and detail. These deficiencies come from various sources including an inadequate description of the chart area; lack of awareness about the area; unavailability of information from the area; the inaccuracy of information about meteorological conditions; and inadequate information obtained from agencies that monitor navigation.
8) There are a few major suppliers of nautical charts, but there are thousands of them all over the world. The number is increasing day by day since many new countries have started to develop their own charting services instead of relying on other countries for them.
9) In certain cases, nautical charts may even miss dangers which risk the safety of ships. This is because there is a difference in opinion among the experts about how much danger should be shown when an area is charted or not charted at all.
10) Finally nautical charts need continuous updating because data recorded in them becomes obsolete in a very short time period. For example, a chart recorded in 1763 may not have been updated since then in spite of significant developments including changing shorelines and advances in shipbuilding technology. It must be noted that shorelines change every year due to various factors such as erosion and accretion.