University of Virginia
Physics Department

## Sonar - Bathymetry

A Physical Science Activity

2003 Virginia SOLs

• PS.1
• PS.8

Objectives

Students will

• explore the applications of sound waves, specifically sonar;
• graph data from a spreadsheet.

Background Information

Sonar stands for Sound Navigation Ranging. It is a process used to map sea floors or observe other obstacles underwater. It works by emitting a small burst of sound from a ship. The sound is reflected off the bottom of the body of water. The time that it takes for the reflected pulse to be received corresponds to the depth of the water. Often, the body of water will be traversed in paths like a grid and every point below the surface will not be monitored. The distance between data points depends on the size of the body of water and the size of the vehicle taking the measurements. Using the data, contour maps of the bottoms of bodies of water are made. Maps that show the contours under bodies of water through depth soundings are called bathymetric maps. They are analogous to topographic maps that are made to show contours of land that are not immersed in water.

### Student Activity

Materials

• Computer with Microsoft Excel
• Copy of the sonar data file ("SonarData.xls")

Procedure

1. Open the sonar data file in Microsoft Excel. The sonar data file contains a spreadsheet with data, and a sample output graph for "Lake Katie." The data is arranged in a grid, with each cell corresponding to a place on the lake. Each number is the amount of time that it took the sound to bounce off the bottom of the lake and return in that spot.
2. Use the data to make a graph of the bottom of Lake Katie. You should use the "Surface" Chart Type.

Extensions

Have the students look at pictures of real sonar maps from http://terraweb.wr.usgs.gov/TRS/kids/MontereySonar/ or other sources. Have them discuss other possible uses for sonar, such as submarine navigation.

Students with Special Needs

Each student should be able to participate in this activity.

Click here for further information on laboratories with students with special needs.

Assessment

Graph to be completed during the laboratory.