Echo sounder and Navigational instrument

Echo sounder noun - A measuring instrument that sends out an acoustic pulse in water and measures distances in terms of the time for the echo of the pulse to return.

Navigational instrument and echo sounder are semantically related. In some cases you can use "Navigational instrument" instead a noun phrase "Echo sounder".

Navigational instrument noun - An instrument used for navigating.

Echo sounder and navigational instrument are semantically related. Sometimes you can replace phrase "Echo sounder" with "Navigational instrument", this phrases are similar.