In 1641 the treasure-filled Spanish galleon Concepción
set sail for Spain from Havana, Cuba. Days later a hurricane
the ship, and her pilots decided to sail to the nearest Spanish base,
Rico, for repairs. A month later the pilots thought they were
of Puerto Rico, so they sailed due south. They were actually north of
is now the Dominican Republic and a treacherous coral reef. Soon
the Concepción ground into the reef and sank, spilling the
riches that would give the reef its name: Silver Bank.
The Concepción was doomed because the ships pilots
a mistake in determining her location. Location can be expressed in a
of ways (with a street address or map coordinates, for example).
This lesson explores the concept of location and allows students to
their own tools to determine their location on the Earths
Connections to the Curriculum:
- geography, mathematics, natural
science, history, language arts
Connections to the National Geography Standards:
Standard 1: How to use maps and other geographic representations,
and technologies to acquire, process, and report information from a
Standard 17: How to apply geography to interpret the past
Standard 18: How to apply geography to interpret the present and plan
for the future
- One to two hours in the classroom plus a half an hour at home
globe or map with latitude and longitude lines
photocopies of a 6- to 8-inch quadrant with visible degree marks (you
can download a quadrant image from the Event Inventor)
pieces of cardboard roughly the size of the quadrant
12-inch pieces of string
small metal weights that can be tied to the string (e.g., washers, keys,
Students will learn about the historical use of quadrants for navigation,
construct their own quadrants, measure their location, and report and
Tell the story of the Concepción and explain its
(You may want to copy the above map onto a transparency to illustrate
course of the Concepción on an overhead projector.)
Explain that the ships pilots miscalculated their location, and
the role location played in the Concepcións
Review some ways of identifying location. While street addresses
are useful for some purposes, latitude and longitude coordinates are
for others, such as navigating a ship at sea. Explain that
is the angle in degrees north or south of the Equator. Longitude
is the angle in degrees east or west of the Prime Meridian, the
line that connects the poles and runs through Greenwich, England.
Illustrate how latitude and longitude coordinates are used to locate
on a globe or map.
Distribute the supplies.
Instruct the students to make their own quadrants by following these
- Paste the copy of the protractor onto the cardboard, and cut the
along the edges of the protractor copy.
Tie one end of the string around the middle of a drinking
Tie the other end of the string to a weight.
Tape the straw along the straight edge of the cardboard protractor,
sure that the knot in the middle of the straw is at the center of the
Cut the ends of the straw even with the ends of the straight edge.
Tell them they have just made a quadrant and explain what one is.
If youre in the Northern Hemisphere, discuss the North Star
with your students. What is it? Where is it? Let them know they can find
the North Star in two ways: First, using the Big Dipper as a
follow a straight line out from the two stars that make up the end of
bowl of the dipper. The first fairly bright star is Polaris. Second,
locate the end star in the handle of the Little Dipper. This too is
As a homework assignment, ask students to go outside on a clear night.
Have them hold the quadrant so that the straw is at the top and look
the straw (like a telescope) at the North Star. The angle between the
string and the 90 degree line on the quadrant is their latitude in
north of the Equator.
If youre in the Southern Hemisphere, your students can use the
sun to calculate their latitude as explained by the USGS Learning
The straw in your students quadrants plays the role of the pencil in
lesson plan. Your analemma corrections in step four of the USGS activity
will be the reverse of those used in the Northern Hemisphere. (Remind
students never to look directly at the sun.)
In class have students compare their results. One way to show results
is by creating a bar chart that plots the number of students who
various latitude readings.
Ask students to think about the accuracy of their data. How
do their results vary? Discuss how easy or hard it might be to use
a quadrant on a rocking ship. How could students increase the
of their measurements? Would a longer or a narrower straw help?
Suggested Student Assessment:
Extending the Lesson:
quadrant readings (homework check)
Sailors could determine their latitude with quadrants, but to
determine their position, they had to know their longitude as well. Many
of our modern seafaring terms come from the way sailors calculated their
Open a discussion about nautical words and expressions by asking
to list as many of these words as they can. Write some of the words on
the board and discuss their meanings and origins. If the words
and knots are not part of the list, add them, and then ask
Why do we enter information into a logbook? Why are nautical
measured in knots?
Sailors used direction, time, and speed to determine their longitude.
They used a compass to measure direction and a sandglass to measure
To measure speed, sailors tied a knotted piece of rope to a log. When
ship was moving, the crew tossed the log into the sea, and the knotted
rope was pulled overboard. Using a sandglass, sailors kept track of the
time it took the rope to unreel. As the rope passed through their hands,
they counted the number of knots, which were spaced at even intervals.
Because they knew the distance between knots, they could calculate the
Now that they know the origin of knots, can students figure out
the term logbook came from? (The way a log was used on sailing
ships gave rise to other expressions using the word, such as logging in
and out andperhaps most interesting for studentslogging on and off
For another hands-on activity, check out Finding Your
from the Event Inventor.
Gail S. Ludwig of the University of Missouri in Columbia, Missouri, contributed classroom ideas
for Silver Bank.