Is LAT the same as Chart Datum?

The statement that LAT (Lowest Astronomical Tide) is the same as Chart Datum is accurate when considering the context of their application. Chart Datum is a reference level used by hydrographers and mariners for charting and navigation, and LAT is one of the reference points that can be used to establish that datum. However, LAT can vary based on geographic location and local tidal ranges, which makes it more of a dynamic reference in some areas rather than a fixed value.

Chart Datum is often based on the lowest astronomical tide but is determined locally and may also incorporate factors like the highest astronomical tide, seasonal variations, and local developments (such as reclamation and flooding) that affect water levels. Therefore, while both LAT and Chart Datum aim for common educational and navigational purposes, Chart Datum may not universally equate to LAT across different regions, because it can depend on regional tidal patterns.

Thus, the correct answer recognizes that while LAT serves as an essential reference in determining Chart Datum, its variation by location fundamentally illustrates the complexity and local adjustments involved in hydrographic surveying.