Grades 6-8 Lesson Plan - Finding Latitudes and Longitudes

Map 1 Main Page

Core Map: Claudius Ptolemy, "World Map" from his Geography (Ulm, 1482). Newberry Library call number: Ayer *6 P9 1842. (Printable PDF version of the Core Map)

Resources related to Map 1.
Curator's Notes for Map 1.

Overview
Using Ptolemy's map students will find the latitude and longitude of modern and ancient place names. In addition they will analyze Columbus' rationale for sailing west. This lesson could also be done in connection with a geometry lesson.

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

1. identify the the differences between major map projections.
2. practice using coordinates to find place names on a map.
3. identify latitude and longitude and use them to find and describe locations (This can be done jointly with a mathematics teacher).
4. analyze the Renaissance view of the world.
5. analyze the role of Ptolemy's map in Columbus' idea of going east by going west.

Key Terms
projection, equator, latitude, longitude, coordinates

Materials
computer image or an overhead of the core map, a modern map of the world, pencil, blank paper

Time
Three hours

Getting Started

1. Display the core map and discuss with your students who made the map and when it was made. (This map exhibits one of the major views of the world in Columbus' day and helped inform his and other explorer's understanding of the globe.)

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

3. Identify the cardinal points of the compass.

4. Point out major place names. Select "Show Translations" from the menu on the core map and click on the highlighted areas for modern names.

5. Point out and discuss the terms "terra incognita" and "Circulus equinoctualis" (click on the terms to get English translations).

6. Discuss the purposes of and information given by the non-geographic features and aids on the map (including decorative elements, the grid lines, and the faces of the winds, important for both energy and direction). You can select "Winds" from the menu on the core map and click on each highlighted head for some of its characteristics.

7. Have students compare core map briefly (for purposes of orientation) with a modern world map.

8. Ask students to discuss what is not on the core map (for example, which continents and oceans are missing).

9. Discuss what portion of the world, expressed in mathematical terms either as a percentage or a fraction, is not in the map. Guide the discussion by referring to the limits of latitude and longitude that are indicated on the map.

10. Select 4 major projections, describe each, and then have students list the advantages and distortions of each. See Resources for some on-line descriptions and images of common projections and some readily available printed materials that provide simple descriptions of projections. You may want to explain at least one projection from each of the major classes of projection.

11. Have students identify the modern map you are using. The projection used in Ptolemy's map of the world is idiosyncratic, but to which projection does it come closest?

1. Have students locate each of the following place names on Ptolemy's map:
   In Europe and the Mediterranean Sea
   Albion insula
   Ciprus
   Cymbricus
   Danubius flu
   Macedonia
   Morea
   Sardinia
   In Africa
   Libia
   Fortunate insula
   Mauritania
   Nilus flu
   In Asia
   Aurea Chersonesus
   Arabia Felix
   Babilonia
   Caspium mare
   Colchis
   Indus Fl
   Sinus Gangeticus
   Syria
   Taprobana insula

2. Have students identify the approximate latitudes and longitudes of these places, using Ptolemy's coordinates.

3. Have the students locate these places or their modern equivalents in a modern map or atlas and identify the modern latitudes and longitudes of these places.

4. Have the students prepare a table with five columns. The first column should be a list of the places using Ptolemy's spellings, arranged in the order given above, i.e. from west to east. The second column should provide Ptolemy's latitudes and longitudes of the places, as calculated by the students. The third column should give the modern spellings of the places, and the fourth column should give the modern latitudes and longitudes. The fifth column should provide the difference between the calculated latitudes and longitudes.

5. After the students have handed in their tables, collate their results and discuss them aloud in the class. Focusing on the results in the fifth column, develop with the class some explanations for the differences. For example, how much of the measured difference between the ancient and modern longitudes can be accounted for by differences in the prime meridians used in ancient and modern times. Were Ptolemy's coordinates more or less accurate as one moves from west to east on the map? From north to south?

6. Assign the curator's notes to the students as reading homework. Have the students write a brief three-paragraph essay explaining how the inaccuracies in Ptolemy's calculations of longitudinal width of the Eurasian continent might have influenced Columbus' project to reach the east by sailing west.

Evaluation
Using a 4 point scale (4=excellent, 3=good, 2= fair, 1=poor) assess student performance based on the work done in Developing the Lesson.

For 4 points, the student correctly estimates all of the ancient and modern coordinates and correctly calculates the differences between the two. The essay demonstrates the student's mastery of these calculations and their implications for Columbus' project.

For 3 points, the student correctly estimates most of the ancient and modern coordinates and correctly calculates the differences between the two. The essay demonstrates the student's understanding of these calculations and clearly describes their implications for Columbus' project.

For 2 points, the student correctly estimates some of the ancient and modern coordinates and correctly calculates the differences between the two. The essay mentions these calculations and provides a plausible correlation between the calculations and their implications for Columbus' project.

For 1 point, the student correctly estimates a few of the ancient and modern coordinates and calculates the differences between the two. The essay mentions these calculations and suggests that the calculations had an impact on Columbus' project.

Extensions

1. Students can compare the methods of navigation used by Columbus with that used by Captain Cook (see Map 3 - Captain Cook and Hawaii, 1778). Identify what they have in common and how they differ. Students can look up the navigational tools used by each and include them in the comparison of navigational systems. This discussion lends itself to small-group presentations.
2. Using the information about the winds from the core map, design and chart, on a printout of the Roselli portolan chart, a tour of the Mediterranean as it might have been done before the use of the compass (it probably came to the Mediterranean in the early twelfth century). In other words the winds are used both to propel the ship and to navigate. Remember that one seldom left sight of the land and used "landmarks" to assist in navigating. The journey should have at least four ports of call, one of which should be in North Africa.
3. Have students create a matrix of projections using those studied above (including Ptolemy's and your classroom map). The vertical axis lists one map per line and the horizontal axis includes the following columns: Area of least distortion, Area of greatest distortion, Method for drawing, Most common use, Cultural context. Each student fills the resulting boxes using general statements and specific examples.
4. Using Ptolemy's map (that he knew the world was a globe is clear from his map) students write the kind of argument for sailing west to go east that Columbus might have used.
5. Each student presents the course he or she plotted on the Roselli portolan chart with a rationale for each.