Calibrating a DVL Sensor

Definition and Recommendations

DVL calibration means estimation of mechanical misalignments (Heading / Pitch) and estimation of scale factor.

Better results are obtained when the range to bottom is constant. This parameter can be displayed into the DVL_BT channel with ‘altitude’:

If it is not the case, the user may select a time window where it is the case in order to activate the calibration at this period.

Procedure

1.

In INS processing parameters, set the Algorithm to Basic and set the Calibration Mode on Auto:

2.

An absolute reference is required to be activated:

3.

Start the calibration process to be launched in Basic mode.

 

4.

Find below the parameters to be displayed and controlled (a channel is created with calibration computation):

5.

Look at the stability of the estimation and the SD value for each parameter computed.

SF/Heading/Pich AND SF sd / Heading sd / Pitch Sd

Check also that the calibration is switching from None / Coarse and then fine (result channel).

6.

Check also that the calibration is switching from None / Coarse and then fine (result channel).

7.

Read the final values on the Instant values window. These values may be used as new parameters.

If the calibration results are ok, it switches from coarse to fine, and Scale Factor Error heading errorestimation converge to a stable value.The calibration is declared OK when the Scale Factor SD error AND Heading SD error goes under 0.1% and 0.1°.

 

DVL Calibration Troubleshooting

Event	Action
DVL calibration stays to ‘coarse’	Check if the INS is already on fine alignment before the calibration or if altitude mode is maintained by depth or GPS.
DVL calibration goes to ‘fine’ but doesn’t converge	Check if the INS receives DVL Bottomtrack data during the whole calibration and has several GPS fixes at the end of calibration.
DVL calibration is too long	Tighten the DVL SD to 0.05 m/s, but check if neither GPS or DVL will not be rejected by INS.
DVL calibration converge but scale factor error is too high (+/- 0.5%)	Check if the INS has a SVS/SVP input sensor.
DVL calibration converge but to an unsual heading error, above +/-1° from [0° + n*90°] or [45° +n*90°] with n=0;1;2;3	Check how the DVL is mechanically mounted accordingly to the INS.