About the Automatic Range Mode

The sensor has an automatic range mode that is useful to get better quality echograms when the trawl is close to the bottom.

Principle

Range influences the display of echogram images. The smaller the range, the shorter the listening time and the better the quality of images. But if you set a bigger range, data arrives slower which results in poorer image quality.

You can activate the automatic range mode if you need to get better quality echograms when the trawl is close to the bottom. This mode is recommended when bottom trawling.

The echogram can automatically switch to a 20-meter range when the distance to the bottom is less than 20 meters, to a 10-meter range when the distance is less than 10 meters and to a 5-meter range when less than 5 meters.

The change of range depends on the settings configured on Mosa2.
Note: The sensor requires pitch and roll angles within -25°to 25° for automatic range operation.
The image below shows the range changing as the sensor gets closer to the sea bottom. The sensor is configured with a 40-meter sounding range and 1.5-meter trawl opening.

1. Maximum range / 2. Switch to a 20-meter range / 3. Switch to a 10-meter range / 4. Switch to a 5-meter range

Mosa2 settings

The following Sounding Mode options must be set in Mosa2:

  • Automatic Range must be activated.
  • The Mode must be set to Down only.
  • The Trawl Opening:
    • must be lower than 19 meters to be able to switch to a 20-meter range.
    • must be lower than 9 meters to be able to switch to a 10-meter range.
    • must be lower than 4 meters to be able to switch to a 5-meter range.
Note: The trawl opening value sets the minimum distance to see inside the trawl. As a result, if the trawl opening distance is equal or higher than 19, 9 or 4 meters, the sensor will not reduce the range respectively to 20, 10 or 5 meters.

See Configuring the Echo Sounder for details about Mosa2 settings.