SUPPORT > SIDE SCAN IMAGERY > CALCULATING THE DISTANCE TO A TARGET

As mentioned, the sonar display shows the recorded echoes over a period of time, and we have seen how we can calculate the depth below the sonar from this.

However, this also means that the range a target appears to be on the display is not the distance it lies at from the sonar horizontally across the seabed.

To understand why this is the case, consider the triangle shown in the figure opposite.

As the sound waves travel from the sonar, they start to hit the seabed, and each point of contact returns an echo along the shortest path to the sonar.

To work out the actual distance at which a target lies, you need to use the mathematical formula opposite...