This module provides a thorough coverage of map projection principles and properties, information on various map projections, and methodologies for projection selection. Lecture sessions incorporate lectures, classroom discussion, demonstrations and active-learning activities. In the exercises students will assess various map projections for their main properties, and from there, select map projections appropriate for specified land areas and map types or themes. Since computers and software are now available for producing map projections, the emphasis in lessons on projections has shifted away from construction and towards selection. Students of cartography, GIS and remote sensing have a difficult time understanding map projections and often don't know how to select a projection or to specify its properties when making maps. This module forces students to critically read and evaluate the literature and examples on map projections, and to understand the importance of selecting appropriate projections for effective map production.
The instructor will need to insure that students have a solid grasp of map projection properties and principles, as well as how to use these principles and properties to select appropriate projections for various mapping tasks. Useful off-line sources of information include:
Preparation for this module will require that the instructor be familiar with map projections principles and properties, and their application to projection selection. The students will be expected to read the textbook and introductory on-line materials prior to the class and lab. Globes and atlases may need to be provided by the instructor for use in class and lab, as these are difficult for students to obtain. The instructor will also need to insure internet access during class and lab times, and for after class use.
For the exercises, students may print the document or portions of it (especially the graphics) from Netscape to use for reference while answering questions. Students will answer the questions directly on the exercise form and submit their answers to the instructor via the instructors email address. There is a section on each exercise where students place their name and their instructors email address, as well as the exercise number (under Subject, e.g., answers for Exercise Part 1). The instructor will receive student answers on a form that lists the students name, the question numbers and corresponding answers.
Lesson Procedures and Schedules:
This lesson can span two 1-hour and 20 minute lectures and two 2-hour lab sessions, depending on how quickly the students are able to get used to the exercise and answer the questions. They will most likely need to do some of the work outside of class time, so sufficient computer lab time will need to be available after class hours. Timing may need to be modified to suit a three 50-minute lecture course.
1.Lecture/Discussion: Provide an overview of map projection principles and properties. Discuss the effects of altering various properties as shown on numerous map examples. Stress the importance of selecting suitable projections for various land areas and map types or themes. Demonstrate the different distortions of the same land area resulting from projections of varied family, aspect, etc. Suggest suitable projection families for different land areas. Involve the students in discussion by asking them to look at specific projections and identify their properties (family, aspect, etc.) and have them compare distortions between projections. Make sure they are aware of the distrotions associated with certain projection types, e.g., cylindrical projections of the world typically exagerate the higher latitudes. Note that students will need another lecture which goes into more detail on specific projections, their properties (especially the mathematical relationships), and their suitability for representing various land areas and map themes.
2. Demonstration: To assist with the explanations, there are some very useful projection examples on the map projections poster and in the Geographer's Craft Map Projections site. You may have some examples of your own too. Some demonstrations using a relevant video or a centrally lit globe are also useful in helping students to conceptualize the transformation of a spherical surface onto a flat plane.
If you have access to a centrally lit globe, create three surfaces as follows: a) a large rectangular piece of paper to form a cylinder that wraps around the globe; b) a large piece of paper formed into a cone shape that fits over the globe, and c) a large circular piece of paper to form an azimuthal plane. With the lights dimmed, have students gather around the globe and show them how a certain continent looks when projected onto each surface. Illustrate also the difference in grid appearance of each family from different aspects (equatorial, polar, etc.). Have the students describe and compare the appearance of a given land mass as projected onto each surface. Unfortunately only the tangeant case can be demonstrated with the globe. Examples of the secant case can be found in the Geographers Craft Map Projections site.
3. Active Learning Activity: Following the "discussion" described in number 1 above, present the students with more examples of projections and ask them to form groups and identify the properties of the family, case, aspect, central meridian and mathematical relationship. Have them write down their answers, then select a few groups to present their results to the class. At this point, the instructor must guide the discussion by assisting students to understand where they may have made errors, and illustrating how to identify properties correctly.
At this point they should be prepared to answer Part 1 of the exercise. Parts Two and Three may require other lecture periods where the differences in mathematical relationships are discussed and demonstrated at length (note that questions in part 1 ask for the mathematical relationship of various projections but do not require real understanding about the effects of these relationships on map distortion).
This session should take place in the lab. Refer to the on-line exercise which can be completed on-line by filling in the form. Students may wish to make hard copy prints of some of the projections to use while answering questions. Have the students begin the exercise and make sure they understand what is to be done. Observe them as they work. You may have to assist them with the some questions in section one, and with the table in section 2. If they have significant problems with either section, they will need further review of the basic principles and properties of projections during the next class period. If they appear to have a good grasp of map projection basics then the next class can focus on specific projections and map projection selection. The students should be able to complete the exercise within a two hour lab period.
Exercise, Part 1: Basic Projection Principles & Properties
1. Lecture/Discussion: This should primarily be another lecture class where students are given a more indepth coverage of projection types, related distortions, and strategies for appropriate projection selection. The instructor should begin with a brief review of projection properties, followed by a focus on specific map projections within each projection family. The map projections poster offers a fairly good selection of projections from which to describe in more detail. The instructor may wish to have individual portions of the poster made into 35mm or digital slides for viewing during class. When discussing each projection, demonstrate the differences in grid appearance as well as the land area distortion associated with variations on the projection properties (aspect, case, central meridian, perspective, etc.). Show examples of suitable and less suitable uses of each projection so that the students will understand which projections to select for a given land area. Be sure to include examples of the world, and of world regions, continents, and other land masses (e.g,. the United States). In all examples, be sure to point out the different types of distortion of familiar land areas (e.g., continents or the US). Involve the students in the process by asking them to describe projection properties and associated land mass distortions.
The students will also need a discussion and demonstration of appropriate mathematical relationships for various types of map. The instructor must provide good examples of conformal, equivalent (equal area), equidistant and compromise versions of the map projections covered earlier in the lecture (e.g., Lambert Conformal Conic vs. Lambert Azimuthal Equal Area). Point out characteristics associated with each mathematical property by providing comparisons between projections. Make reference to the table on the map projections poster as it lists appropriate uses of a selection of projections.
2. Active Learning Activity: As an active learning exercise, divide students into groups and assign each group with two distinctively different maps (e.g., a general reference map of the world, and a population density map of India). Each group must select an appropriate projection for each assigned map. Their selection must include the projection name, projection family, aspect, case (with specific latitude(s) ), central meridian (with specific longitude), and mathematical relationship. Each group will need to provide reasons for their selections. This discussion should take about 10 minutes. For the remaining class time, have each group present their selections, with rationale, to the class.
Session 4
This lab session will involve completion of Part 2 of the exercise. Part 2 involves comparing four sets of two projections for similarities and differences in properties and distortions. Answers can be submitted on the on-line form. Part 2 is comparatively short, thus, students should have no problem finishing within the two hour lab period.
Exercise, Part 2: Comparing Distortions among Projection Types
Session 5:
Lecture/Discussion: Go over the material covered in previous lectures and help students with problems they might be having with the exercises.
Active Learning Activity: The instructor will need to have several atlases, maps and globes available for this activity. Using a large sheet of tracing paper, have students select one continent or region and trace their selected region from several different projections as found in different atlases and maps. They should trace their region from the globe as well. Since the maps will be at different scales and projections, each tracing should include a central meridian and parallel so that all maps can be centered in the same location. Have students write down the projections used (they may wish to use color pencils to differentiate projections), then analyze their projections for different types of distortion. Each student or pair of students should then go before the class and describe the differences they found between projections.
Session 6:
This is the final lab session. Students will complete Part 3 of the exercise on-line. For this exercise, students will refer to an atlas or globe moreso than to on-line resources, therefore the instructor must provide these. Students may also wish to refer back to the Geographer's Craft Map Projections examples, and to the in-class active learning activity from Session 3.
Exercise, Part 3: Selecting Appropriate Projections
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Created 6/5/97 by Laurie A. B. Garo. Last updated 9/20/00 by
lg.
The URL for this page is http://www.uncc.edu/lagaro/cwg/mapproj/instructor.html