TOF or time of flight is the time that a signal takes to propagate the target, get partial reflected and return to the transmitter. (double the distance to the target) It is used to calculate distance. The signal can be electromagnetic (for example radar and laser) or Newtonian (ultra sound and underwater sonar). The propagation speeds depend on the signal type ; electromagnetic = 2e8 m/s ; air ultrasonics = 400 m/s and sonar = 1400 m/s
The difference in speed of ultra sound and sound is so much !! 400 and 1400 m/s !! sounds little strange. Is there difference of medium too like sea water !
Thanks a lot, the post as serial no #2 gives a feel that the two speeds (sound and ultra sound) travel at very much different velocities so the issue. It is clear now.
and to be really pedantic, it depends on pressure, temperature and humidity. Even the speed of light varies in the atmosphere depending on the pressure, temperature and humidity. It can cause noticeable errors if you want high accuracy but ignore it.