Neil's News

Range Finder

31 December 2012

A surplus satellite dish unexpectedly entered my possession. Let's measure distances using the speed of sound. I secured my phone's microphone to the focal point.

[Using a satellite dish for sonar]

Next, I pointed the dish at an apartment building at the other end of the block. I am not fond of this particular apartment building because it blocks my view of the Bay. So acquiring exact targeting information will be useful for future experiments.

[Aiming the dish at a building]

Clapping my hands once produced a recording (WAV) which forms the wave pattern below. A small but clear echo shows up exactly 0.258 seconds after the clap.

[Wave pattern of echo]

Dividing by two (outward journey and return journey) and multiplying by the speed of sound at sea level gives a distance of 43.9 meters. Measuring the same distance on Google Earth gives a distance of 43.1 meters.

[Google Earth map]

Only a 2% disagreement between two wildly different methods of measuring distance. Not bad.

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