
A 23 mm calibration sphere for 120 kHz
In order to calibrate the ME70, a reference target (calibration sphere) with known target strength (TS) is lowered into the all beams. The measured target strength is compared with the known target strength of the sphere, and the ME70 is adjusted accordingly.
To successfully calibrate the ME70 you need to place a number of target detections in the beams. The echoes must be evenly distributed within the entire distribution of beams. In order to do this, the target sphere must be physically moved inside the distribution of beams during the calibration process.
Each beam mode to be used in a survey must be calibrated separately. For each beam, new estimates for adjusting gain and sA correction must be calculated using the target strength data and the reference sphere values.
Any adjustments to the ME70are done automatically by the calibration program. No gain adjustments are required.
The information provided by the calibration is entered into the ME70 software as operational parameters. This is done automatically.
TipWe recommend that you calibrate the ME70 in calm sea.
In rough sea with heave compensation activated, the calibration sphere will move up and down in the echogram. This is because the sphere follows the vessel motions, while the ME70 attempts to compensate for the same motions. In order to detect the sphere, you may even need to expand the depth limitation.
You can suppress the heave compensation by disabling the input from the sensor. However, this will remove the heave compensation information from the raw data that you record. It will then be missing if you wish to assess the calibration later using the replay functionality.