When we read data from our fish finder, we usually imagine that the information we see on our screen is all happening directly under our sonar. So, if we see a fish on the screen, we think it must be exactly underneath our sonar. In reality, the readings we see are taken from a wider area underneath our sonar. And even more importantly, the sonar receives data from a wider and wider area, the deeper you scan. This is all because sonars scan in cones.
SONAR stands for SOund NAvigation Ranging. A sonar device sends pulses of sound waves down through the water. When these pulses hit objects like fish, vegetation or the bottom, they are reflected back to the surface. The sonar device measures how long it takes for the sound wave to travel down, hit an object and then bounce back up. It’s the same echo-location system bats and dolphins use. This information enables the device to judge the depth of the object it reflected off. It also measures the strength of the returning pulse – the harder the objects, the stronger the return pulse.
Once a returning pulse is received, another one is sent out. Because sound waves travel at roughly one mile a second in water, sonars can send multiple pulses per second. The Deeper PRO, Deeper PRO+, Deeper PRO+ 2, and Deeper CHIRP 2 send 15 pulses per second. The returning sound pulses are converted into electrical signals and then displayed, showing anglers the depth and hardness of the bottom and any objects in between.