There's one question so far tagged ultrasonic. I am far more used to those sensors being referred to as sonars. I'm wondering if my perception is the most common or if people do use ultrasonic/ultrasound more often, and whether we should replace the tag or establish them as synonyms.


"Ultrasonic" seems like an odd tag to have -- like having separate tags for "LED" and "Red LED". It's still sonar; the only reason it's ultrasonic is because nobody wants to listen to the sound a rangefinder makes.

In the AUV industry, sonar is a broad term for a lot of sophisticated (but very separate) technologies. The simplest active sonar devices measure range only, but others measure the speed of currents / speed over ground (DVLs) or provide imaging capabilities (sidescan, DIDSON). There is also a large use of passive sonar, which can't really be called ultrasonic because it doesn't produce sound.

Update 11/29/12: I think the best thing to do might be to break these out by the function of the sensor, in a "how-what" format. For example:

  • acoustic rangefinder (could also say "sonic")
  • laser rangefinder
  • acoustic imaging
  • laser imaging (lidar)
  • doppler velocimeter
  • $\begingroup$ Even though @ronalchn has a point that the two are not strictly synonyms, I'd expect people to conflate the two most of the time and would err on the side of user expectation over correctness of definition. $\endgroup$ – ThomasH Nov 29 '12 at 18:27
  • $\begingroup$ User expectation is certainly a good thing to favor, but I'm hesitant to fully agree with you. The vast majority of users probably work with terrestrial robots (and not UAVs/drones or AUVs/subs), but those other types of robots are no less valid. In other words, catering to one user group would be fine if it didn't come at the expense of clarity for another group. I'll amend my response to incorporate this. $\endgroup$ – Ian Nov 29 '12 at 18:57

Strictly speaking, sonar and ultrasonic sensors are related, but slightly different concepts. For more information, see Sonar or Ultrasonic sensor on Wikipedia.

Ultrasonic sensors use high frequency sound waves, and calculate the time interval between generating and receiving the echo. They are used to detect the presence of a target, or measure the distance to the target.

Sonar stands for SOund Navigation And Ranging. The acoustic frequency used does not have to be ultrasonic (above human hearing range), and can include all sound frequencies, including infrasonic frequencies (below human hearing range). It includes active and passive sonar.

Sonar systems may involve multiple sound transmitters, and sensors, and may involve more complex data processing.

  • $\begingroup$ Very fair point. I happily muddled the two together without thinking about it. However, the question the still is, are they similar enough to make them one tag, or tag synonyms at least? Or should we leave it be until the first sonar question actually comes up? $\endgroup$ – ThomasH Oct 30 '12 at 15:16

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