Navigation and Nautical Charts Quiz

Navigation Principles

• Required reading for the course: Dutton's Nautical Navigation, 15th edition (chapters 2, 3, and 8)

Enabling Objectives

• Students need to know terms related to the Earth's coordinate system, including Equator, Prime Meridian, Great Circle, Small Circle, Parallel, Meridian, Latitude, Longitude, and Rhumb Line.
• Students should understand projection concepts and the primary map projections used in navigation.
• Students need to know the strengths and weaknesses of Mercator and Gnomonic Projections.
• Students should understand the distinctions between Great Circle Routes and Rhumb Lines.
• Understanding how to use a Nautical Chart is vital, as well as the main nautical chart concepts.
• Students need to understand how charts are distributed and the function of Chart One.
• Students should know how to read directions, latitude, and longitude on a nautical chart.
• Students should know the length of a degree of latitude and longitude.
• Basic plotting tools are needed for navigation.

Terrestrial Coordinate System - Latitude

• The equator is the baseline for measuring latitude.
• Latitude measures angular distance north or south of the equator (0° - 90°).
• Latitude is expressed in degrees, minutes, and seconds, followed by 'N' or 'S'.

Terrestrial Coordinate System - Longitude

• The Prime Meridian is the baseline for measuring longitude.
• Longitude measures angular distance east or west of the Prime Meridian (0° - 180°).
• Longitude is expressed in degrees, minutes, and seconds, followed by 'E' or 'W'.

Terrestrial Coordinate System

• A combination of latitude and longitude defines a position on the Earth's grid.
• An example of coordinates is given for the Riverside Observatory.

Great Circle and Small Circle

• Great Circle: A circle on the Earth's surface that passes through the Earth's center.
• Small Circle: A circle on the Earth's surface that does not pass through the Earth's center.

Meridian

• Meridian: A great circle that passes through the Earth's poles.

Equator

• Equator: A great circle that is halfway between the Earth's poles.

Projections

• Most nautical charts use the Mercator Projection.
• Rhumb lines and parallels are shown as straight lines on a Mercator projection.
• Meridians and parallels are perpendicular to each other.

Mercator Projection (Advantages)

• Latitude and longitude appear as a rectangular grid, making it easy to plot positions on the chart.
• Determining latitude and longitude for a plotted position is straightforward.
• Measuring distances is easy using the latitude scale (1' = 1 nautical mile).
• The four cardinal directions are easily located on the chart.

Mercator Projection (Disadvantages)

• Great circle distances are not readily determinable.
• Extreme latitude regions show significant distortion.
• Poles are not represented on the chart.

Nautical Charts

• A nautical chart is a graphic representation showing a maritime area and the adjacent coastal regions.
• Charts display water depths and land elevations, natural features of the seabed, coastline details, navigational hazards, and locations of natural and man-made navigational aids.
• Charts also show information on tides , currents, the Earth's magnetic field variation), and man-made structures like bridges and harbors.

Nautical Charts Distribution Agencies

• National Ocean Service (NOS) , a division of the National Oceanic and Atmospheric Administration (NOAA), is responsible for coastal US waters, most rivers, and the Great Lakes for commercial and civilian use.
• Army Corps of Engineers, including tributary rivers and some inland lakes.
• The National Geospatial-Intelligence Agency (NGA), formerly NIMA, handles charts for the Department of Defense and international use.

Nautical Charts Title Block

• Region identification, main title, projection, scale information, publisher, datum information, depth and elevation notes, cautionary notes, and tidal information are present in a nautical chart title block.

Nautical Charts Datum

• Datum is a reference point for measurements on nautical charts.
• Horizontal Datum: Refers to the Earth's surface for distance measurements.
• Vertical Datum: Used for height (sounding) measurements.

Nautical Charts Datum Shift

• Datum shift is the difference between the actual and plotted position on a chart when using different datums (chart and GPS).

Nautical Charts Chart Scale

• Chart scale is the ratio between a distance unit on the chart and the corresponding distance on the Earth's surface.
• Example: A scale of 1:20,000 means one unit on the chart represents 20,000 units on the surface of the Earth.

Comparing Scales

• Larger scales are used for areas close to the dangers such as harbors or entrances.
• Smaller scales are used when one is far away from dangers, such as when underway at sea.
• Prefer the larger scale when in doubt.

Nautical Chart Components: Compass Rose

• Used to measure true or magnetic directions using a parallel ruler.
• Indicates local variation and annual change in direction.

Nautical Chart Components: Distance Scale

• Used with a compass or divider to measure distances on the chart.

Nautical Charts Chart One

• A valuable aid for new chart users.
• Provides basic chart symbols and abbreviations used in paper and electronic nautical charts.
• Included in it are symbols for rocks, wrecks, and obstructions

Plotting Latitude and Longitude

• Steps to locate a specific position on a chart using latitude and longitude.
• Latitude and longitude are used together to establish a position.

Reading Latitude and Longitude

• Explanation of the units (degrees, minutes, seconds) used for latitude and longitude.
• Demonstrates determining lattitude and longitude using a chart.

Reading Distance

• Length of a degree of latitude is constant at 60 nautical miles (NM).
• Length of a degree of longitude changes depending on latitude.

Navigation Tools: Slider Ruler

• Used to measure distances and directions on a nautical chart.
• Ensures that the slider ruler has the correct scale of the chart.

Reading Directions

• Explains how to read directions using a nautical chart.
• Example of using a compass rose to measure true North.