Chart datum
= Chart datum
{wiki=Chart_datum}
Chart datum is a reference level used in nautical and hydrographic charts to measure water depths. It is an important concept in maritime navigation, as it provides a standard baseline from which depths and heights are measured. Chart datum is usually defined as a specific level of a tidal system, and it can be based on various criteria, such as mean sea level, lowest astronomical tide (LAT), or mean low water springs (MLWS).