How Do You Read Nautical Chart Sounding?

Sailing is an adventure that requires knowledge and precision in order to be safe on the waters, and one of the most important tools for navigating is a nautical chart sounding.

Having a good understanding of how to read these soundings can help you stay safe and get where you’re going quickly and accurately, even when you’re out in unfamiliar waters. In this article we’ll discuss what nautical chart soundings are, how to interpret them, and what other details you should pay attention to when sailing with charts in hand.

What Is a Nautical Chart Sounding?

A nautical chart sounding is an indication of water depth shown on a nautical chart, usually measured in feet or fathoms (one fathom equals 6 feet). These soundings are created by surveying the shoreline or other shallow areas with depth-measuring instruments, such as echo-sounders or lead lines, then recording them onto a chart for reference when planning a course or navigating waterways.

How To Interpret Soundings On a Chart

Soundings on charts are represented by numbers showing depths at various points along the coastline or other areas surrounding your sailing route, for example, “3 fathoms” indicates that there is 3 fathoms (18 feet) of water at that particular point along the shoreline.

The presence of negative numbers indicates shallower water than indicated by the number, for example, “-2 fathoms” means there is 2 fathoms (12 feet) less than what’s indicated by the number (i.e., 10 feet).

Understanding Mean Lower Low Water (MLLW)

The soundings printed on the chart normally represent the depth at mean lower low water (MLLW), which means that actual depths may be more than what’s shown on the chart due to tides or other factors affecting water levels such as storms or floods, however, when tide tables show negative low-tide entries, actual depths will be less than what’s indicated by the charted depths.

Tidal Effects on Depths Shown on the Chart

It’s important to remember that tides have an effect on depths shown on charts – if you’re navigating during high tide, for example, your actual depth may be more than what’s indicated by the chart because of tidal effects pushing up water levels, conversely, during low tide your actual depth may be less than what’s indicated due to tidal effects lowering water levels below what’s shown on charts. It’s always best to consult local tide tables before setting out so you can plan accordingly for any tidal effects that may affect your journey’s progress.

What Are The Different Types of Soundings?

Nautical charts usually contain different types of soundings which provide information about different aspects of navigation, these include: isolated deeps (water deeper than its surroundings), isolated shoals (water shallower than its surroundings), contours (lines showing changes in depth over an area), wreck locations (locations where ships have sunken with their cargo intact), buoys, lights and lighthouses (markers used as navigational aids).

How To Read The Contours Of a Nautical Chart

The contours printed onto nautical charts typically represent changes in depth over an area, these lines become closer together as they move away from land and indicate shallow waters near land masses while wider spacing indicates deeper waters further away from shorelines – it’s important to take note of contours when plotting courses so you know how deep or shallow certain areas are before entering them!

What Is “Dead Reckoning” and How Does it Relate to Reading Charts?

Dead reckoning is an age-old technique used by sailors for centuries which involves plotting courses from one point to another based solely upon current speed and direction, this technique can be used alongside nautical charts for more accurate navigation as it allows sailors to take into account any changes in currents or winds that might affect their journey’s progress – it’s important for all sailors to have a good understanding of dead reckoning before heading out into unfamiliar waters!

Understanding Buoy Markers and How To Read Them

Buoys are markers placed along navigable waterways which provide information about conditions such as currents, wind direction and speed, these markers also indicate hazards such as shoals or rocky areas near shorelines which should be avoided – it’s important for all sailors taking courses through unfamiliar waters to pay close attention to buoy markers as they provide invaluable information about conditions along their journey’s route!

Reading Lights And Lighthouses On Charts

Lights and lighthouses serve as navigational aids which help sailors stay safe while navigating unfamiliar waters – they provide directional clues about course changes needed in order for sailors stay within safe passages while avoiding any hazards that might exist nearby – these lights can usually be seen from quite far away so it’s important for all sailors taking courses through unfamiliar waters pay close attention when reading lighthouses and lights printed onto their nautical charts!


Reading nautical chart soundings can seem daunting at first but with practice it will become second nature – having knowledge about mean lower low water levels, tidal effects and buoy markers will give any sailor greater confidence when plotting courses through unfamiliar waters! Remember too that dead reckoning can also prove invaluable when crossing uncharted seas! With enough experience anyone can become an expert sailor so don’t hesitate – grab your compass and get out there!

Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *