About Trawl Positioning

This topic explains how the position of the trawl is calculated.



Angles are relative to the stern of the vessel. Angles toward port side are negative and angles toward starboard side are positive.

The distance is calculated from the warp lengths sent by a winch control system. Scala2 application can calculate the positioning of the trawl from this distance, the depth and bearing angle.

The distance between the two hydrophones (2) is called the baseline (1).

To have positioning data, the system must have the following equipment:
  • 2 receiving hydrophones:
    • 2 passive hydrophones + wideband preamplifier (ref NC-2-02)
    • OR 2 active wideband hydrophones (ref. NC-1-08)
  • Warp lengths
  • Baseline calculation
  • GPS and heading input
Important: The two receiving hydrophones must have a minimum distance of 1 meter between each other.
Important: You need to remove the 50kHz notch filter on the wideband preamplifiers.
Important: On M4 and M6 systems, the receiving hydrophones must be both connected to a hydrophone input between H1, H2 and H3 or both between H4, H5 and H6. The transmitting hydrophone must be connected to a different set of hydrophone inputs than the receiving hydrophones (for example, if the receiving hydrophones are connected to H1 and H2, the transmitting hydrophone must be connected to a hydrophone input between H4, H5 and H6).