From 3-D to Flatland and Back Again


Objectives:

Students lean how to read contour maps and, by extension, physical relief maps by working through various activities of which some simulate contour mapping and others require use of actual contour maps. These exercises will help the students understand land forms and topography when looking at two-dimensional maps and images, including remote sensing images.

Time Duration: two 50-minute sessions

Grade Level: 6-9

Concepts Explored: observation, analysis, measurement

Vocabulary:
contour, contour line, elevation, land forms, relief, topography, valley

Materials Day 1:

Materials Day 2:

Description:

This lesson deals with looking first at an actual 3-D situation, the first day, and then using such information to work with 2-D maps and images. It also involves learning to understand changes in perspective from a horizontal or oblique view to an aerial or bird's eye view. Such a change reflects dramatic changes in human technology for viewing the earth.

From a horizontal perspective we can see land forms and heights, but we get a distortion in shape and size. What we see in the foreground seems larger than what is in the background, and we can see the detail in the foreground objects better than in the objects in the background. An aerial perspective gives us a different, perhaps more accurate, view although we do lose a sense of scale, unless we remember what we have learned from looking at contour and physical relief maps.

Remote sensing, employing thermal infrared wavelengths, digital scanning and chemical techniques as well as aerial and satellite photography, offers a fuller range of options for viewing the earth and making maps and images for whatever portion of the earth we wish to observe. These studies in turn are confirmed by additional ground-truth research. It must be remembered that the initial mapping of the USA was done at ground level.

Procedure for Day 1:

Part 1:

  1. Assign students to teams of two.

  2. One student from each pair should make one of his/her hands into a fist with the knuckles at the base of the fingers (hereafter referred to as the top knuckles) pointing upward and the thumb tucked underneath and around the fingers.


    (See Figure 1 above.)

    The other student should prepare a maker by placing it on top of a block or other support and securing it with a rubber band.

  3. The student doing the making should hold the marker and block in place and make a line of equal "elevation" above the desk or table top around the hand of the other student's middle knuckles, across the sides of the hand and the front of the thumb, and over the wrist as that student moves his/her hand. The student doing the marking should be sure to include the indentations that the fingers make where they touch each other (very important for demonstrating one of the land forms). Line A, Figure 1.

  4. Next, the student doing the marking should draw a line around the hand midway between the middle and top knuckles. Line B, Figure 1.

  5. The student doing the marking should then draw a line around the top of the knuckles. Line C, Figure 1.

  6. The students should then trade roles and repeat steps 3, 4, and 5.

  7. Each student should look at his/her fist in this position. It not only is a fist in 3-D, but it also can represent a range of hills or mountains with valleys in between, some of which could have been formed by streams and rivers. What do the top knuckles represent? Is one of the knuckles higher than the highest line drawn around the hand? What does that mean? Where are the valleys? Which side of the "mountains" is the steepest? With their fists in this position the students are essentially looking at them from a horizontal or oblique view.

  8. Now each student should flatten out his/her hand with the fingers slightly apart and straight and look at it from above. This is the aerial or "bird's eye" view. By looking at the lines and noting how the indentations form Vs that point toward the top knuckles, can you tell where the high points and valleys are? Where are the lines farther apart? Closer together? What do the relative locations of these lines mean? (Think back to the fist.) By flattening you hand you have made a contour map - a 2-D representation of a 3-D situation. The lines you drew on your fist correspond to contour lines and thus give much information about topography by their shapes and relative locations.

Part 2:

  1. Working individually, the students should examine their own copy of the contour map from Naturescope, Geology, p. 41. They should look for the high points, the low points such as the creek, the valleys, the marshland. Can they determine where the hills are steeper or more gradual? Do they think determining land forms from this perspective is easy? With experience they should find it easier to decide what the relief or the topography of any land area is when they look at a contour map.

  2. With the contour map flat on a desk or table, each student places a narrow strip of stiff paper or cardboard, such as one cut from a file folder, across as many of the contour levels as possible including the creek area. Then each student should make a short tick mark on the strip where the it intersects a contour line and write the contour level in feet next to each tick mark. Once this step is completed, each student should then place the strip along the bottom of the horizontal grid sheet provided, make an "x" at the appropriate elevation level for each tick mark and connect the marks on the grid to give a horizontal perspective of the contour map.

    [Caution! Between the marks adjacent to the stream the student should make a V-shape that does not dip to the next lower contour level. In a similar way with the hills, the student should make rounded lines between the contour levels at the same elevation that do not touch the next higher contour level.]

  3. Another method for transferring information from the contour map to the grid can be found in Activity Sheet #4 from What Do Maps Show? In fact, the entire exercise could be done using the materials from this map kit instead of from Naturescope.

  4. The students should be encouraged to observe and compare the two different perspectives of the same area, then discuss them.

Procedure for Day 2:

  1. Following the completion of the lesson in day 1, the students should again be assigned to work in pairs.

  2. They should then proceed to follow the directions given in Naturescope, Geology, pp. 35-36, for making a cardboard contoured land form. The students can then cover the contoured land form with aluminum foil and carefully mold the foil to the contours to obtain the actual shape.

  3. An alternative to the cardboard model involves cutting out colored construction paper, one color for each contour level, and putting together the construction paper contours in the same way as the cardboard, but this can involve the use and waste of a lot of colored paper.

  4. An extension to this exercise involves building the same contoured shape with clear acetate sheets or clean, clear plastic snack boxes and then placing them on top of one another in the proper order.

  5. With the materials from the previous exercises available for them to use, the students should next look at the photos and images from their community building project (if available), the USGS materials for Salt Lake City, and the contour and physical relief maps and remote sensing images for OTTER, compare them and be prepared to discuss them with the class.

  6. In comparing the contour and physical relief maps, can they determine what the heights of the shadows mean in the physical relief maps? Can they find similar land forms in the OTTER images? Can they find ridges or other high places in the OTTER images? Valleys? Rivers or streams? Human artifacts such as roads? At which altitude above ground level can they begin to see these details in the images? What purpose does each image serve? Which of the altitude images corresponds better to the contour or physical relief maps? These questions and others should help the student to become more comfortable with observing and analyzing facts provided by maps and remote sensing images.

Extensions:

This activity is suggested to help with understanding scale and resolution. In this case, the observer stands still and the object moves toward the observer.

  1. Suggest that students go outside their homes in the evening after dark and watch for airplanes landing at a nearby airport. When they first see a plane approaching, what do they actually see? As the plane gets closer, what details can they begin to see? The large white lights? The red and green lights? The shape of the plane? The location of the various lights and actual parts of the plane? The students are observing change in resolution, in detail as the plane flies closer to them. In a similar way, remote sensing images have different scales of resolution depending upon the altitudes at which they were obtained and the purposes for which they were obtained. How much detail is necessary for the desired information? Is the information wanted for a large or small area? These questions and others are ones that can be asked during the study of the OTTER area as well as other areas. From looking at the OTTER remote sensing images, what different details can be seen? In the image from 450 miles above (an AVHRR image)? From 65,000 feet above (a Daedalus TMS image)? From 12,000 feet above (a TIMS image)? From 5,000 feet above (a CASI image)? From 1500 feet above (a digital video image)? In which images can rivers and highways be seen? Vegetation differences? Human effects? Elevation differences?

  2. Assign a couple of students to seek information from nearby airports about the distance in miles from an observer when the observer begins to see various details about an approaching airplane.



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