STONY BROOK, New York—Modern cartography can be extremely accurate thanks to the development of satellite technology that allows precise calculations of distances between a satellite traveling in space and various points on the earth's surface below. And thanks to a clever teacher, a bit of plastic tarp, and an ultrasonic rangefinder, students at Robert Cushman Murphy Junior High School are learning to use the same technological approach to create precision contour maps in Philip Medina's eighth- and ninth-grade science classes.

Using the ceiling tiles as a mapping grid, Medina hangs a 20-foot by 40-foot plastic tarp from his classroom ceiling. He uses paper clips and tape to create variations in the tarp's surface, simulating a geographical representation of the earth's surface. Medina says, "The trick here is not to have too many steep areas. Gently rolling hills are best. Too many hills or too steep sides will give values that are too difficult to work with." When the faux landform is in place, Medina uses spray paint to add rivers and lakes to depressions in the plastic and assigns names to "mountains" at higher elevations. He also labels specific sites where students will be asked to calculate the gradient of the land.

In class, small groups of students are each given a laptop computer, a computer probe interface with an ultrasonic rangefinder, and graph paper. They then use the ultrasonic rangefinder to measure the distance from a moveable desktop—a desk on wheels that can be maneuvered to keep the height of the rangefinder constant as it moves beneath the ceiling tile grid—to various points on the map above. "It works by echolocation like a dolphin or bat," says Medina. "The signal is emitted, hits an object, and bounces back to the sensor. The computer times the round-trip and calculates a one-way distance from that."

The data collected by the students is recorded on graph paper and later input into a software spreadsheet. Once the data is entered into this computer program, a surface plot can be generated. This surface plot can be rotated 360 degrees in any direction. The image can also be manipulated to add contour mapping lines.

Through the project, "students are given a realistic activity to complement class learning," says Medina. "The activity mimics the way that current maps are made using satellite technology. The project also includes spreadsheets in a way students rarely use: to generate a three-dimensional surface. In addition, the images, which are easily rotated, reinforce the relationship between contour lines and land features such as peaks, valleys, and gradients."

Located in a Long Island suburban community, Murphy Junior High School serves 900 students of primarily Caucasian and some Asian descent. With a large university and technology lab in the area, Medina says the school benefits from "a well-educated and technologically oriented parent population." Better than 90 percent of students have access to a home computer with Internet access. At school, Medina's class, like others, is well equipped. He has enough laptops so that each student can have his or her own in class, as well as a desktop with Internet access and a linked projector permanently mounted on his ceiling.

Of the mapping project, Medina says, "My students love the activity because it is so high-tech. It's a little tedious for them to collect all the data [roughly 70 data points] but they can also work on sections and share data. The 'a-ha!' comes when they make the last command in the spreadsheet program and the surface plot pops up. Then a genuine chorus of 'cool!' erupts when I show them how to rotate the picture. Finally, if they change the point-of-view to directly above the surface, it results in a traditional contour map showing concentric circles of color showing change in elevation."