Topic: Deciphering a Chart and Topographic Map
Primary Goal: Introduce students to how to read, decode, and decipher a nautical chart and topographic map.
Š Ability to read and identify key features of nautical charts and topographic maps
Š Identify the similarities and differences between charts and maps
Š Describe different situations in which you could utilize a chart or map
I. Key features of a Nautical Chart
a. Water depths
b. Different types of sea bottom (rock, sand, mud, wrecks, reef)
c. Buoys and daymarkers
d. Aids to navigation
i. Provides information to safely navigate a vessel to reach your desired location
II. Who provides this information?
a. NOAA (National Oceanic and Atmospheric Administration)
b. NOS (National Ocean Service)
III. What do all the letters and numbers on a chart mean?
a. Since charts include a great deal of information, we use a great deal of symbols and abbreviations
b. Discuss some abbreviations from “Chart No. 1” publication
IV. Latitude & Longitude
a. System of geographic coordinates used to describe a specific location on the earth’s surface
i. Measured in degrees, minutes, seconds
b. Meridians of Longitude – lines that specify the east-west position of a point on the Earth's surface
i. Passes through north and south poles
c. Parallels of Latitude – lines that specify the north-south position of a point on the Earth's surface
i. Measured by how many degrees a point is north or south from the equator
V. Chart Projection System
a. Since the world is not flat (but your paper charts are) mapmakers project the earth’s curved surface in two dimensions
b. Mercator Projection – most popular projection used for nautical charts
i. Flattens out the earth so that lines of latitude and longitude form a rectangular grid that you can measure
c. Use example of peeling an orange and attempting to lay flat
VI. How can we use Latitude and Longitude on a chart?
a. To share or record your own location
b. To determine the exact location of a place you would like to go
c. To measure distance (only using latitude)
d. Have students get in groups and do “Shipwreck Exercise”
As you identify the different features on a chart, have students identify examples on the charts provided to them.
Provide charts and have students break up into groups. Explain that you have just come across information that there is a sunken treasure ship somewhere on the chart and provide students with a Latitude and Longitude. They must identify the location of the shipwreck on the chart.