Glossary Archive

The horizontal movement of water caused by the rise and fall of the tide. A tidal stream refers to the flow of water generated by the gravitational pull of the moon and the sun, which causes the sea level to rise and fall in a cyclical manner. This movement of water is distinct from ocean...

A collection of charts that depict the set (direction) and rate (speed) of tidal currents at various stages of the tidal cycle. A Tidal Stream Atlas is an essential navigational tool used by mariners to understand the movement of water caused by tides in a specific area. These atlases provide detailed information about the direction...

The rise and fall of sea levels caused by the gravitational forces of the moon and the sun acting on the Earth's oceans. Tides are characterised by regular and predictable patterns, with two high tides and two low tides occurring approximately every 24 hours and 50 minutes. Tides are crucial in marine ecosystems, navigation, and...

Charts or listings that provide the predicted times and heights of high and low tides for specific coastal locations over a given period. Tide tables are essential tools for mariners, fishermen, and anyone involved in coastal activities, as they offer crucial information about the timing and magnitude of tidal changes. These tables are typically presented...

A lever attached to the rudder head by which the helmsman moves the rudder

A measure used in satellite navigation systems, such as GPS, to quantify the effect of errors in the timing of satellite signals on the accuracy of position calculations. It represents how much the timing errors in the satellite signals dilute the overall precision of the position solution. A lower TDOP value indicates better timing accuracy...

A measure used primarily in maritime and aviation contexts to estimate the time until two moving objects (e.g., ships or aircraft) reach their closest point of proximity to each other, assuming their current courses and speeds remain unchanged. It is a crucial parameter in collision avoidance systems. Key Concepts: Closest Point of Approach (CPA): The...

Estimated time remaining to a waypoint giving an indication of arrival time

A region of the Earth where the same standard time is used. A time zone is a geographical area that observes a uniform standard time for legal, commercial, and social purposes. The Earth is divided into 24 primary time zones, each generally corresponding to 15 degrees of longitude, reflecting the Earth's rotation and the division...

Flag semaphore indicating the letter T.