In hydrography, the (static) draft is the offset between the bottom of the echosounder's transducer and the water surface. This is normally a fixed value and should not change very often. Some echosounders allow you to define this draft in the echosounder's configuration.
In cases in which it isn't possible to set the draft in the echosounder, you can also configure the draft in Hydromagic. To do so, open the "Preferences Dialog" by selecting "Preferences" from the "Options" menu. Click the "Calibration" tab and enter the (positive) offset or draft here.
For instance, if the difference between the waterline and the transducer is 40 cm, enter 0.40 here.
Please make sure you do not enter this value in both your sounder and the Hydromagic software !
