Land Use Lesson 2 : Measuring Land Use and Land Cover
1. Vocabulary development: dot planimeter.
In this lesson, students use a dot planimeter. While they can use it without understanding what the term means, insight into the term will be helpful. Write the following terms on the board: pedometer, thermometer, speedometer, tachometer, anemometer, and dot planimeter. Ask students if they know what any of the terms mean. If they do or think they do, write their definitions next to the terms.
Next, ask: What do all of these words have in common? [They end with the suffix -meter.] If students knew the meaning of some of the terms, you may be able to use their definitions to deduce that when a term ends with the suffix -meter, the term is the name of a device that measures something. Otherwise you may have to simply tell them the meaning of the suffix.
Use one of the more familiar terms, such as thermometer or speedometer, to demonstrate that the first part of the term tells what is measured (in these cases, heat or speed.) Focus students’ attention on the term dot planimeter. What do you already know just by looking at the word? [It describes a device for measuring something.] Explain that one meaning of plane is a two dimensional space. Given that information, What might a planimeter be? [A device for measuring space.] Explain that the term dot is used because the planimeter the students will be applying uses dots as a way to measure space.
2. Introduce the value of photographs.
Tell students they are going to be considering evidence they can get from photographs. Display a photograph (or poster) of a well-known person or family photograph (of the teacher or family) and ask: Who is this? How do you know it is that person? What criteria did you use to be certain the picture is who you think it is? [Facial appearance; hair style; and smile or expression.]
What are the advantages and disadvantages of photography as a scientific tool? [Advantages: It is a record of information, and it portrays items in a realistic way. Disadvantages: It is limited to the visual; provides only one perspective; can be altered; and is valid for only the time it was taken.]
What would a photograph look like if it were taken from a hot air balloon or airplane? (Review the Kite View Air Photograph in Lesson 1. It would show only the tops of everything on the ground. Some students may suggest that it is a bird’s-eye view.) Ask students to help identify things in a photograph taken from an airplane. Additional photos from http://www.kiteseyeview.com may be used to identify other recognizable objects on the earth’s surface. See Additional Resources in Lesson 1 for additional websites.
3. Define land use and how it can be classified.
(See teacher Advance Preparation for the way land use was classified on Map 1: Land Use and Land Cover: The Imprint of People.)
Distribute the student resource, Air Photo or Map 1: Land Use and Land Cover: The Imprint of People, to pairs of students and have them list the things that they see on the air photo on a separate sheet of paper. [Trees, fields, houses, garages.]
Ask each pair of students to classify what they observed on the air photo. The air photo has lines that enclose land use or land cover classes (i.e., residential, recreation, forests, water, and open space). Explain that water in lakes and rivers is a land cover. The lake may have several different uses, such as recreation, fishing, water for a nearby city, etc.
For each land use in the air photo key, students should assign a symbol. Then on the air photo they enter the symbol to indicate the land use. This same symbol should also be placed in the “Key.” For example, if a tree is used for forest, a tree should be used in this area on the air photo and put in the box next to “Forest” on the key.
Summarize, in a group discussion, the classifications the students applied to each area on the air photo. Ask students to give specific examples of information from the air photos that led them to classify its land use or land cover in a particular way. For example, the forests represent a land cover whereas the houses represent a land use (residential). Review the classification shown in Air Photo 1: Land Use and Land Cover: The Imprint of People answer key.
A natural resource is something provided by nature and used by people. What is the natural resource used by each of the categories on the air photo? [Land.] Each class of things in the air photo uses land as a resource. What is the use of this resource called? [Land use.]
4. Consider how to estimate the amount of land in each land use (land cover) category.
Pose the following questions to students:
Can we estimate what land use or land cover has the greatest area on the air photo? [Yes, we can, but the estimate may not be very accurate.]
How might you determine the amount of land used in each of your classifications on the air photo? List student ideas about how the areas in each category might be determined. These ideas may include using a grid pattern or a dot planimeter.
5. Introduce the dot planimeter as a way of measuring areas.
Show the dot planimeter transparency on the overhead projector. Explain that by counting the dots in each area, we can get a fairly accurate measure of the amount of land in each area. Remember that the Background Information mentioned having students measure the size of a baseball infield. Scientists can use the dot planimeter to measure square miles and acres. As you continue the lesson, students will be counting dots from the dot planimeter and comparing the areas of land use and land cover. [Note: Students will need a transparency copy of the dot planimeter to place on the air photo. They can then see and count the dots that are enclosed with each land use classification.] Demonstrate how this might work.
6. Complete the data table.
Distribute the dot planimeter transparency and acetate pen to each pair of students. Have them lay it over their student resource (Air Photo 1 or Map 1: Land Use and Land Cover: The Imprint of People). Tell pairs of students to count the dots in each area of the air photo and record the numbers in the Amount of Area for Each Land Use/Land Cover student activity page. Explain that some areas with the same land uses are on different parts of the air photo. Students must sum the dots for all of the areas that represent each classification of land use.
Since dots may fall exactly on lines on Map 1 or Air Photo 1, a rule is needed for where to include those dots in the classification of land use. Read-right-up (RRU) is the rule to explain to students. Count the dots in the land use space towards the top of the photo if it is a horizontal line, or to the right if it is a vertical line.
Amount of Area for Each Land Use/Land Cover Answer Key
| Land Use/Land Cover Classification | Number of Dots out of 100 | Percentage |
| a. Forests | 19 | 19 |
| b. Recreation | 22 | 22 |
| c. Residential | 37 | 37 |
| d. Water | 4 | 4 |
| e. Open Space | 18 | 18 |
The students should use the number of dots to make comparisons regarding the amount of land use in each classification. They can convert the land uses to percentages if they are familiar with percentages. This presents an opportunity for the teacher to demonstrate that percentages are based upon 100 and, since there are 100 dots on the dot planimeter, then each dot represents one percent of the area on the map.
7. Analyze the data.
Have the students convert the land use data table to a bar graph on the student activity sheet, Bar Graph of Land Use/Land Cover, and answer the following questions as a class discussion led by the teacher.
Which land use is most prominent on Air Photo 1? [Residential.]
Is it a human or natural land use? [Human.]
Why are there several different land uses, rather than not just one land use on the entire air photo? [Some land is better suited for particular uses, land is often zoned for a use and sometimes there is no pressure to change one land use to another. People make choices about how the land is used.]
Do people or the natural environment appear to have the most influence over land use based on this air photo? [People.]
Which land uses suggest the most human impact? [Residential has the most human impact.]
(Note: The forested areas may have once been logged and are now second or third growth. The actual impact of humans historically may be much greater than what shows on the land use and land cover pattern today.)
Which land uses might have the most economic value? Why? [Residential is most valuable since it has a high investment.]
8. Review.
Is land a resource? [Yes. Land is a very important natural resource.]
Does all land use and land cover look the same? [No. In looking at an air photo, it is easy to recognize that some places have water, which is a land cover, and other places have houses, which is a land use. There are several different classes of land use and land cover.]
Is all land suitable for the same use? [No, some land is wet; other land is dry. They may serve very different purposes.]
Do people have different responses to different kinds of land use and land cover? [Yes, some people prefer land uses with houses; others prefer agriculture land use.]
Is some land more valuable than other land? [Yes, land that is wanted by the most people is often considered the most valuable. People like to live along lakes. As a result, land that is along the lake often costs more money. Parks and natural resources are also valuable based on the recreation activities they provide.]
Why is some land more valuable than other land? [Some land has minerals or precious metals; land is also well suited for special uses, such as farming; land with a high demand for a specific use is often more valuable than land that has a particular location or may be valuable as a site for a particular use.]