NAUTICAL CHARTS Who needs them? Can anyone explain the purpose of a Nautical Chart? (let them answer) A chart onboard allows you to compare what you are seeing with what you should be seeing and can help you keep your bearings. Who needs them?

NAUTICAL CHARTS Nautical charts are different from maps in that they specifically depict water areas, while maps concentrate on land area, roads, landmarks, etc. Land areas and features on charts are sketchy and are noted only for their interest to the boater. Unlike maps, the nautical chart conveys much information specifically designed to assist in safely navigating the area that the chart covers Nautical charts are different from maps in that they specifically depict water areas. Land areas and features on charts are sketchy, meaning that there is not much detail/it is just a rough outline, and are noted only for their interest to the boater Nautical charts are specifically designed to assist in safely navigating the area

NAUTICAL CHARTS Important tips: Study your chart thoroughly. Look at the position from which you will start and visually follow along the course you wish to take. Look for "notes" - water depths, obstructions (especially under water), bridges, power lines or any other unusual items that may be a hazard to your progress. Look for visual objects featured on your chart that you should be able to observe and identify to confirm your position. When utilizing a Nautical Chart, even for reference you want to: Study the area that your chart covers or the area you intend to be at What are some of the things you should look for? Yes you want to pay attention to notes, water depths, obstructions or any other items that my be a hazard Look for visual objects on your chat that you should be able to observe and identify to confirm your position.

NAUTICAL CHARTS SMALL SCALE CHART LARGE SCALE CHART 1:100,000 EVERYTHING APPEARS SMALL – less detail. 1:100,000 MEANS 1 INCH ON THE CHART IS 100,000 INCHES ON THE EARTH’S SURFACE. LARGE SCALE CHART You have multiple scales of charts, but 2 main types, small and large scale. On small scale charts everything appears small so there is less detail, So on small scale charts, as shown, 1:100,000 means that 1 inch on the chart is equal to 100,000 inches on the earths surface Whereas on a large scale chart everything is larger so there are more details. And 1:1,000 means that 1 inch on the chart is equal to 1,000 inches on the earth’s surface. EVERYTHING APPEARS LARGE – more details. 1:1,000 MEANS 1 INCH ON THE CHART IS 1,000 INCHES ON THE EARTH’S SURFACE.

NAUTICAL CHARTS 1:80,000 Small Scale 1:25,000 Large Scale Here are examples of the difference between a small scale chart and a large scale chart. Notice that, in the small scale, the Harbor is just a solid color, there are no soundings, and there are no lights or buoys. Now on the bottom right you see a closer view, of the same harbor, but in a larger scale. Now you can see lights, buoys, soundings and harbor entrance 1:25,000 Large Scale

NAUTICAL CHARTS CHART TITLE Now to use a Nautical Chart you have to understand some basic features: a. Every chart has a title. It will be larger than the rest of the print and can also be found by the chart number in the margin

NAUTICAL CHARTS CHART ORIENTATION TRUE NORTH is at the top of the chart. EAST is at the right-hand side of the chart. WEST is at the left-hand side of the chart. SOUTH is at the bottom of the chart. Charts are always oriented with True North at the top, East on the right hand side of the chart, West on the left hand side of the chart and South at the bottom of the chart.

NAUTICAL CHARTS MAGNETIC NORTH TRUE NORTH THE COMPASS ROSE Every Chart has a compass rose. The compass rose is used to get bearings from landmarks, or buoys The star on the Compass Rose points to True North. Where the North pole actually is The inner circle projects Magnetic North. Which shows the pull from earths magnetic field

NAUTICAL CHARTS SOUNDINGS Soundings are in meters, feet, or fathoms (6 feet per 1 fathom) Numbers which reflect the depth of the water Colors - shallow water is tinted a darker blue and deeper water is a lighter blue and white. 1. All chart measure the depth of the water in meters, feet, or fathoms. A fathom is a measurement that 1 fathom equals 6 feet and is only used in water depths. 2. Each chart will show the unit of measurement in the margin 3. No chart will have more than one unit of measurement for soundings

NAUTICAL CHARTS SOUNDINGS CONT. Depths of water are the mean depth for that area. Water depth can be affected by the storms, the moon, wrecks, and shoaling. Onshore winds can increase the depth of water. Offshore winds can decrease the depth of water and/or delay its predicted depth time. It is important to know that soundings are only the average depth for that area, which means that depths can be higher or lower than the printed depth What are some factors that would cause the water depth to change? (if they get stuck here is a hint, think about tides!) 2. The reason they are only an average depth if because water depth can be affected by storms, wrecks, shoaling, or general daily tides. Note: For any particular location, the height and fluctuation of tides depends to varying degrees on the location of the Sun and the Moon, and to the details of the shape of the beach, coastline, coastline depth and prevailing ocean currents

LIGHTS AND AIDS TO NAVIGATION (ATON) NAUTICAL CHARTS LIGHTS AND AIDS TO NAVIGATION (ATON) There are numerous different types and configurations of aids to navigations (ATON’s). In fact way too many and way to complicated to go over. Can anyone tell me what this is and what it is for? (buoys can be used to mark channels, bays, wrecks and sometimes have horns or whistles which aid mariners in navigating during foggy conditions.)

NAUTICAL CHARTS TYPES OF BOTTOMS There are 39 different types of bottoms for the ocean floor. If an area’s bottom is known it will be displayed on the chart M = Mud The type of ocean floor is important information for fisherman, wade fishers, marine biologist, and vessels anchoring in that area There are 39 different types of ocean floors. Harbor charts will annotate what type of ocean floor was observed In this example the “M” means that the ocean floor is made up of mud. Does anyone know what type of bottom comprises a good part of San Francisco Bay? (mud and silt)