How-to Singlebeam Settings

This How-to describes step by step how to enter the settings for a Singlebeam Echosounder system into QINSy.

There are three ways of doing this:

  1. Using the conventional way of entering the values of bar check and heave compensation into the echosounder itself.
  2. Using the way of entering values into the echosounder and also into the program.
  3. By way of not entering values into the echosounder but only in QINSy.

 We will describe the advantages and disadvantages of using each method. 
 To further enhance your understanding of this part of the program, please also read the additional notes we have added.

On this page:

1 Corrections to the echosounder

  • Determine the echosounder draft by doing a bar check
  • Determine the sound velocity by barcheck or with a sound velocity profiler
  • Enter these values into the echosounder
  • Connect the heave compensator to the echosounder

To enter the values into the database carry out the following steps:

  1. If you are starting a new set of data: Use our Knowledge Base document 'Getting Started - 2. QINSy Database Setup' to set up your echosounder.
  2. If your echosounder is already entered into the Setup program: From the QINSy Console go to Setup - Action - Db Setup - double click on your Single Beam Echosounder in the system tree.
    The Edit System dialog will appear. Next> Next> will bring you to the Singlebeam Echosounder Parameters page.

Singlebeam Echosounder Parameters window in conventional mode with echosounder values entered:

Processing

The depth measurement is not reprocessed in QINSy. This means that the original depth value from the echosounder is combined with the position for the transducer and this height will be the end result.

Use the following settings:

  1. Echosounder is draft corrected (checked).
  2. Correction derived from node offsets or Enter manually do not affect the final result as the depths are not re-processed.
  3. Used velocity does not affect the final result as it is not used in the computations.
  4. Echosounder is heave compensated (checked).

    Heave

    Make sure that the heave interfaced into the echosounder is the heave at the transducer location.

    If the heave is not for the transducer location QINSy will show a ripple which cannot be corrected for afterwards.

  5. Depths require no re-processing (checked).
  6. If squat corrections are required then Superimpose squat should be checked.

Advantages of using this method

  • The database can be set up in one session. After the bar check no more changes are required in the database.
  • What you see is what you get. The values in the QPD (processed data files of QPS software) are the same as can be read from the echosounder roll.
  • It is not required to input the draft in the QINSy Controller.

Disadvantages of using this method

  • It is not possible to switch to Accurate Height or to Replay with Accurate Height.
  • It is not possible to Replay with a different sound velocity value or with a different sound velocity profile.
  • With large pitch/roll values the depths "on the roll" may be incorrect due to the fact that the slant range is greater than the depth.

2 Corrections into the echosounder and into the program

  • Set up the vessel and measure all nodes accurately.
  • Measure the motion sensor (node & C-Os)
  • Carry out a bar check and enter draft and sound velocity into the echo sounder AND ALSO into the Singlebeam Echosounder Parameters page (see description above).
  • Determine the draft at the CoG and enter this value online at the draft settings. (Online - Settings - Computation Setup).

Singlebeam Echosounder Parameters window with echosounder values entered plus values for calculations:

Processing

The depth measurement is reprocessed in QINSy. This means that the original depth value from the echosounder is calculated back to the travel time of the pulse between the transducer and the seabed. From the depth measurement the Draft correction is subtracted and optionally the heave. The result is divided by the Used Velocity to give the travel time.
This travel time is used to calculate the depth of the seabed by  multiplying with the Calibrated Velocity or using a Sound Velocity Profile (Online setting under echosounder settings/refraction). Combined with the Node height for the transducer the height of the seabed is calculated.

Use the following settings:

  1. Echosounder is draft corrected (checked).
  2. Enter manually the value as used on the echosounder.
  3. Used velocity as used on the echosounder.
  4. Echosounder is heave compensated (checked) if compensator is connected to the echosounder.

    Heave

    Make sure that the heave interfaced into the echosounder is the heave at the transducer location.

    If the heave is not for the transducer location QINSy will show a ripple which cannot be corrected for afterwards.

  5. Footprint placed vertically below transducer (checked).
  6. Except when pitch/roll is outside transducer beam angle can be selected if required. This is the most correct option.
  7. Calibrated velocity is the same velocity as found with bar check. This value can later be used (if required) to correct for an incorrectly used sound velocity.

Advantages of using this method

  • It is possible to work/replay in Accurate mode (RTK height).
  • It is possible to replay with a different sound velocity or with a sound velocity profile.
  • As a check the height of the singlebeam node must represent the height as found during the bar check (when idle). If this is not the case the draft of the CoG is incorrect.

Disadvantages of using this method

  • Values for (echosounder) draft and sound velocity need to be entered in the database.
  • Draft at CoG must be determined and entered online. (However this is essential when working with a second sounding system).

Echosounder Other Parameters

Used sound velocity
To be able to work with soundvelocity profiles, it is necessary to know how the echosounder calculates depth. For this it needs to know which velocity was used in the echosounder. Now it is possible to calculate the travel time. When the travel time is known different soundvelocities can be used, or profiles if required.

Depth unit
Here you can select which units are output by the echosounder.

Echosounder is heave compensated
This box should be ticked when the heave compensator is directly connected to the echosounder. This tells QINSy that the data from the echosounder is already compensated and it does not apply heave compensation any more. This also opens the option to do no re-processing of the depths received from the echosounder.

Footprint Calculation

Depths require no re-processing
Select this option if you want to use the depths of the echosounder directly without any re-calculating.

Superimpose squat
If squat correction is required and 'Depths require no re-processing' is selected this mode can be selected.

Footprint calculated using pitch/roll (see at bottom of page).
When this option is selected the pitch and roll are used to calculate the horizontal position of the footprint. Also a slant range correction is calculated for the measured range.

Footprint placed vertically below transducer
When this option is selected the footprint will be located directly under the transducer. No slant range correction will be applied.

Except when pitch/roll is outside transducer beam angle
With this option ticked a slant range and footprint correction will be made when the pitch/roll are outside the beam angle. This mode is based on the fact that the echosounder detects the first return within the beam width. If the roll/pitch values do not exeed the beam width no slant range/footprint corrections are needed.

Calibrated velocity
If the calibrated soundvelocity is different from the one used in the echosounder then it can be entered here. It is not used when a soundvelocity profile is enabled for the echosounder. This option can be used if a survey is done with an incorrect soundvelocity and a replay is required.

3 Raw data output / No corrections into the echosounder (preferred option)

In this case you can have two scenarios:

  1. Raw data output and corrected on echosounder echogram/roll
    1. Echosounder id outputting raw depth observation (option on Deso, Navisound, ect)
    2. Heave is interfaced into Echosounder and into the QINSy
    3. Draft is entered on the Echosounder and into QINSy.
    4. Tide is interfaced into QINSy (and into the Echosounder if possible)
  2. No corrections interfaced 

For both of the above scenarios you need to:

  • Set up the vessel and measure all nodes accurately.
  • Measure the motion sensor (node & C-Os)
  • Carry out a bar check and enter sound velocity into the Singlebeam Echosounder Parameters page (see description at top).
  • Determine the draft at the CoG and enter this value online at the draft settings. (Online - Settings - Computation Setup)

Singlebeam Echosounder Parameters window with unused echosounder values plus values for calculations:

Processing

The depth measurement is reprocessed in QINSy. This means that the original depth value from the echosounder is calculated back to the travel time of the pulse between the transducer and the seabed. From the depth measurement the no Draft correction needs to be subtracted as it is not entered in the echosounder. The result is divided by the Used Velocity to give the travel time. The Used Velocity is fixed at 1500 in the echosounder and database setup.
This travel time is used to calculate the depth of the seabed by  multiplying with the Calibrated Velocity or using a Sound Velocity Profile (Online setting under echosounder settings/refraction). Combined with the Node height for the transducer the correct height of the seabed can be calculated.
With this setup, all corrections on calculations are done through QINSy. The echosounder only acts as a medium to pass on raw, uncorrected depths.

  1. Echosounder is draft corrected (not checked).
  2. Enter manually is empty.
  3. Used velocity not filled in.
  4. Echosounder is heave compensated (not checked).
  5. Footprint placed vertically below transducer (checked).
    Except when pitch/roll is outside transducer beam angle can be selected if required.
    This is the most correct option.
  6. Calibrated velocity is the velocity as found with the bar check.
    This value is used to compute depths.

Advantages of using this method

  • A fictional draft and sound velocity can be entered into the echosounder.
    The machine can be placed somewhere unaccessible, not to be touched or the settings adjusted.
    All corrections are entered in QINSy.
  • All settings can be altered in Replay mode if necessary.

Disadvantages of using this method

  • Because you cannot see the roll in the echosounder you can't see what is happening immediately.

Some additional notes on how QINSy calculates depths

The node height is calculated by antenna height, pitch and roll when in Accurate Height mode.
The node height is calculated by draft, tide and squat when in Unreliable Height mode.

When the vessel's draft changes the new value should be entered Online under Settings - Computation Setup - Manual draft

For more information about the use of heights in the calculations use our Knowledge Base document "Howto Height".

Using pitch/roll

When using an echosounder with a single beam the following can occur: especially when sailing up or down a slope the beam width determines the recorded position of a depth. The wider the beam, the larger the shift in position will be. When the pitch of the survey vessel is added the beam will tilt and cause a further shift in the slope position.
See the illustration for the effects of choosing to check the options 'Footprint calculated using pitch/roll' or 'Except when pitch/roll is outside transducer beam angle'.

Position A: Middle of black bundle represents the correct depth at the correct position.
Left side of the red bundle is the depth; projection of the centre provides the position.

Position B: Right side of tbe black bundle is the depth; projection of the centre provides the position.
Right side of the red bundle is the recorded depth; projection of the centre gives the position.