Grades 3-5 Lesson Plan - Of Compasses, Sextants and Chronometers

Map 3 Main Page

Core Map: William Bligh, "Chart of the Sandwich Islands," from James Cook and James King, A Voyage to the Pacific Ocean…in the Years 1776, 1777, 1778, 1779, and 1780, 2nd. Ed. 3 vols. London: G. Nicol and T. Cadell, 1785. Newberry call Number: Case fG 13.19 Vol. 3 opp. 2. (Printable PDF version of the Core Map)

Resources related to Map 3.
Curator's Notes for Map 3.

Overview
In this unit students will use the core map to explore basic eighteenth-century maritime navigation including the finding of latitude and longitude. It is strongly recommended that teachers review the concepts of latitude and longitude and earth-sun relationships with students prior to using this lesson.

Objectives
By the end of this lesson students are expected to:

1. identify longitude and latitude and how they were, and are, determined.
   
2. discuss the rudiments of navigation in the eighteenth century.

Materials
computer image or overhead of the core map, copies of the core map, Longitude Worksheet, a modern map of Hawaii, protractor, compass, coloring pencils, construction paper, glue or tape, scissors

Time
Two hours

Getting Started

1. Display the core map. Discuss with students who made the map and when it was made.

2. Have students identify major geographic features and the symbols Captain Cook used.

3. Eliciting as much information as possible from the students, identify the cardinal points of the compass.

4. Point out major place names. To reveal modern day place names, select "show place names" from the menu on the core map.

5. Point out and discuss the phrases "foul ground" and "no ground" (near the number 160; meaning that the depth is greater than 160 fathoms. See also the Curator's Notes).

6. Discuss the purposes of and information given by the non-geographic features and aids on the map (including decorative elements, and grid lines).

7. Compare core map briefly (for purposes of orientation) to a modern map of Hawaii.

1. Have students draw an eight-point compass rose (i.e. north, northeast, east, southeast, south, southwest, west, northwest) on a small piece of construction paper. Discuss how we orient ourselves by north, south etc. It would be especially useful here to use local geography, e.g. North Main Street, East 4th Avenue, and so on.

2. Discuss the use of the compass points in travel by indicating the direction from the school to other significant places, e.g. the state capital or a local shopping center.

3. Identify north, south, east, and west on the core map. Have students cut out the compass rose and attach it to the core map without covering significant information.

4. Follow the route of Cook's second encounter with Hawaii in December 1778 and January 1779 (indicated by a solid zig-zagging line). Point out to the students that the dates marked on the map indicate the position of Cook's ships on those dates.

5. With the aid of a globe and referring to the information in the curator's notes, discuss why the observations were made at noon. Discuss how measuring the angle of the sun above the horizon with a sextant allowed navigators to determine the latitude.

6. Using a globe or world map discuss what time it would have been in London when it was noon in Hawaii. Discuss how these time differences and a chronometer set to London time (Greenwich Mean Time) would help a navigator determine his or her longitude. Remember that 15º equals one hour since 360º equals twenty-four hours.
7. Using available maps, atlases, or globes, have students complete the Longitude Worksheet. First, students are to determine the longitudes of the cities listed on the worksheet. The longitudes should be rounded to the nearest degree and expressed as 0-180 west of Greenwich or 0-180 degrees east of Greenwich. Using these figures, students should then calculate the solar time (rounding to the nearest hour) in these places when it is noon in Greenwich. Please note that the conventional times, determined by modern time zones, may not be the same as true solar time, which is based solely on the daily transit of the Sun. Remember that a one hour time difference is equal to 15 degrees longitude.

For 4 points, the student has correctly calculated at least 90% (36 of 40) of the longitudes and time differences.

For 3 points, the student has correctly calculated at least 80% (32 of 40) of the longitudes and time differences.

For 2 points, the student has correctly calculated at least 70% (28 of 40) of the longitudes and time differences.

For 1 point, the student has correctly calculated at least 60% (24 of 40) of the longitudes and time differences.

Extension
On a clean paper version of the core map, students should plot a journey, distinctly different from Cook's, of at least two weeks, with a minimum of ten different noon positions marked. Compass readings should be given. Have the students extrapolate from the latitude and longitude lines on the map to calculate daily longitude and latitude readings. The time on the chronometer (Greenwich Mean Time) should also be given.