May/June, 2003, Earth Science Experiment: Terrain Mapping	- Purpose - Background Information - Equipment & Supplies - Experimental Procedure - Data Analysis - Conclusions and Extensions

Background Information:

Spacecraft such as the shuttle Endeavour and NASA's Mars Global Surveyor use instruments called laser altimeters to measure their altitude above surface features. Beams of light are bounced off land surfaces to determine the height of mountains and slopes and the depth of features such as valleys and craters. In a similar fashion, PASCO's Motion Sensors can be used to measure "altitude" above features of a land surface designed by students. The sensors emit ultrasonic pulses and receive back echoes of those pulses in order to calculate how far away objects are. (What animals use a similar means to determine their position with respect to objects in their environment?)

Consider some of the reasons why geologists or other environmental scientists might want information about surface features of landforms. Seismic studies depend on accurately measuring the location of faults both aboveground and underground. Measuring the height of geological structures such as mountains allow scientists to track processes that change Earth's shape over time. Determining the extent to which erosion has affected a slope will also depend on accurate measurements of surface features. What are other applications of terrain mapping?

Hypothesize: In this activity you will construct your own sample "landscape" using materials in your classroom. Predict what each of your "surface features" will look like on the graph display as a plot of your terrain is constructed.

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Equipment and Supplies:

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Experimental Procedure:

1. Create a "landform" by arranging a variety of objects in a row on the floor. Use whatever materials are at hand -- chairs, books, personal belongings, even people. A Motion Sensor will "fly" over the landscape at a distance of 1.0 meter above the surface (the floor), so be sure that all structures are less than 1 meter in height.
   
   
2. The person "flying" the Motion Sensor over the terrain must be able to move near and across the landscape in such a way as to not disturb the features of the land mass.

Data Collection & Recording

1. Connect the Motion Sensor to the interface. Carry the interface and Motion Sensor to the edge of the "landscape." Turn the sensor so that it points straight down at the floor. Position it so that the sensor is 1.0 meter above the floor.
   
   
2. Click the Start/Stop ( ) button on the Xplorer or the LOG button on the 500 interface to begin recording data. Begin moving horizontally at a constant speed and constant height above the landscape so that the Motion Sensor can record its position above each landscape feature.
   
   
3. Continue moving at a slow, constant speed until you have "flown over" each landscape feature.
   
   
4. When you reach the end of the landscape, click the Start/Stop ( ) button on the Xplorer or the LOG button on the 500 interface to end data collection.
   
   
5. Reconnect the interface to the computer and download the data you collected.
   
   
6. Repeat for multiple trials and for multiple landscape formations as time permits.

Data Analysis:

1. Examine the Graph Display to view your data, using the Scale to Fit button ( ) in the Graph toolbar to resize the axes as needed.
   
   
2. Use the Statistics button ( ) in the Graph display to find the minimum, maximum and mean values for the distances to the terrain's surface features. Compare any differences between data runs. Sketch and describe the key features of your terrain.
   
   
3. Why is it important that the Motion Sensor "fly" at a constant height above the surface features? How would the data change if the sensor changed its altitude during the flyover?

Conclusions and Extensions:

1. Challenge lab groups to create different, original "landscapes" that can be analyzed with the Motion Sensor. One group's data can be given to a second group, who must then determine what objects may have been used to create each feature of the terrain.
   
   
2. Research how many spacecraft have used laser altimetry in a similar fashion to map the terrestrial features of Earth, Mars and other bodies in space.