Tide tables, sometimes called tide charts, are used for tidal prediction and show the daily times and levels of high and low tides, usually for a particular location.[1] Tide heights at intermediate times (between high and low water) can be approximated by using the rule of twelfths or more accurately calculated by using a published tidal curve for the location. Tide levels are typically given relative to a low-water vertical datum, e.g. the mean lower low water (MLLW) datum in the US.[2]