What is the nadir of a tow-fish side scanner?

The nadir of a tow-fish side scanner refers to the point on the seabed that is directly beneath the center of the tow-fish. This is crucial in hydrographic surveying as it helps define the exact location from which the sonar's acoustic signals are transmitted and received, providing detailed images and data of the underwater terrain. Understanding the nadir is important for accurately interpreting the collected sonar data, as it establishes a reference point for the imagery and measurements taken.

In this context, the center of the tow-fish serves as the ideal point to determine the nadir because it is the position from which the sonar emanates and captures data directly below. This ensures that the readings reflect the conditions and features of the sea floor as accurately as possible.