Qimera Manage Filter Profiles Dialog


How to Start

This dialog is launched via the icon on the Filter Operation Toolbar.

What it Does

This dialog allows the user to create, import, edit and remove custom filter profiles. Filter profiles are a set of operations which are applied sequentially to a set of soundings. Filter operations can modify soundings in a number of ways, most commonly by rejecting undesirable soundings, but also through modifying flag data or shifting sounding position.

Note that filters run from the Filter Toolbar will set the 'Filter' bit in the QPD when rejecting points.  By doing so, we can differentiate these rejected soundings from soundings rejected via manual editing in the Swath, Slice and 3D Editors (these set the 'Manual Edit' flag).  This allows you to apply and revert filters using the filter toolbar without being worried about losing any manual editing that may have been done.

The dialog is divided into two main halves: filter profile management happens on the left, while the profiles and their constituent operations are edited on the right. The profile selected on the left dictates which profile is edited on the right.

Profile Management

Profiles List

This list contains all the custom profiles that the user has created or imported.

New

This button creates a new, empty filter profile after asking for a profile name.

Import

This button imports a filter profile from a file. Both Qimera's own .profile format as well as Qloud's .qfd file formats are supported. Please note, however, that not all of Qloud's filter operations have a perfect equivalent in Qimera, so profiles should always be reviewed for subtle discrepancies after import.

Copy

This button duplicates the currently selected profile after asking for a new profile name.

Rename

Renames the currently selected profile after asking for a new name.

Remove

Removes the currently selected profile after asking for confirmation.

Profile Editing

Operations List

This list shows all of the operations making up the current profile along with their editable parameters.  Operation names are shown in bold. Operation parameters are shown across two columns with the name on the left and the value on the right. Click on a parameter value to edit it.

Add New Operation

This button shows the Add Filter Operation dialog, allowing you to choose a new operation to be appended to the profile.

This dialog lists the names all of the available operations on the left. Selecting an operation name shows a description of that operation in the Details pane on the right. Click OK to add the selected operation or Cancel to cancel.

See the Available Filter Operations section for more information on the individual operations.

Remove Operation

This button removes the selected operation from the list.

Move Operation Up

This button moves the selected operation up in the list of operations. Operations higher in the list are executed before the operations that follow them.

Move Operation Down

This button moves the selected operation down in the list of operations. Operations lower in the list are executed before the operations that precede them.

Available Filter Operations

Qimera has several filter operations which can be combined to produce interesting results. See below for a list of all operations and a brief description of what they do.

Reject Above Height

Rejects all soundings above the specified height.

Parameters:

  • Height

Reject Below Height

Rejects all soundings below the specified height.

Parameters:

  • Height

Reject Using Surface Spline (Preset)

Fits a 3D spline surface through noisy point data and rejects all soundings that are too far from the surface. The spline type is chosen from a list of presets.

The 3D spline surface is a representation of the local topography built using approximately 50-100 soundings at a time. The surface is calculated using a weighted least squares method through the available soundings. The surface is area based and takes contributions from many survey lines simultaneously. The criteria for spike detection depends on the expected sounding vertical accuracy, which scales with filter strength. Strong filters filter more data than weak filters.

The ROV Depth is positive downward and is added to the sounding depth (which is most likely negative) to reference the sounding to be relative to the sensor as opposed to the water surface.

The Reference Depth can be used to adjust the reduced soundings to get back to values relative to the water level. This can be used, for example, when working on a lake where the depths can be very large when referenced to mean sea level. The reference depth is subtracted from the reduced soundings.

The Rejection Preference is used to specify which soundings are rejected in relation to the computed spline depth.  The options are Reject Above and Below, Reject Above and Reject Below.

Parameters:

  • Spline Type
  • ROV Depth
  • Reference Depth
  • Rejection Preference

Reject Using Surface Spline (Custom)

Fits a 3D spline surface through noisy point data and rejects all soundings that are too far from the surface. The spline type is chosen by manually specifying all parameters.

The 3D spline surface is a representation of the local topography built using approximately 50-100 soundings at a time. The surface is calculated using a weighted least squares method through the available soundings. The surface is area based and takes contributions from many survey lines simultaneously. The criteria for spike detection depends on the expected sounding vertical accuracy

Increase the minimum point count to allow the filter to better model the seafloor, this comes at the expense of increased processing time.

Expected accuracy is expressed in percentage of water depth.

First and second pass SD factor is a scaling factor applied to the standard deviation that controls two consecutive spline fitting passes. Low values filter strongly, high values filter weakly. The first pass SD should not be too high to ensure that blunders are eliminated on the first pass to allow for a better fit on the 2nd pass.

The ROV Depth is positive downward and is added to the sounding depth (which is most likely negative) to reference the sounding to be relative to the sensor as opposed to the water surface.

The Reference Depth can be used to adjust the reduced soundings to get back to values relative to the water level. This can be used, for example, when working on a lake where the depths can be very large when referenced to mean sea level. The reference depth is subtracted from the reduced soundings.

The Rejection Preference is used to specify which soundings are rejected in relation to the computed spline depth.  The options are Reject Above and Below, Reject Above and Reject Below.

Parameters:

  • Minimum Point Count
  • Expected Sounding Vertical Accuracy
  • First Pass SD
  • Second Pass SD
  • ROV Depth
  • Reference Depth
  • Rejection Preference

Reject Using Vertical Spline

Rejects soundings by fitting a vertically-oriented, 3D spline to the soundings and rejecting outliers from that spline.

This filter is only appropriate for filtering vertical surfaces such as quay walls and will work best in combination with an area polygon selection.

The higher the detail of the spline, the fewer soundings will be rejected.

Parameters:

  • Spline Type
  • ROV Depth

Reject Specific Beams

Rejects all soundings from the specified beam(s).

The Beams to Disable are specified by a comma separate list of ranges. For example "1-10, 48, 52, 91-100"

Parameters:

  • Beams to Disable

Reject All Soundings

Rejects all soundings within the selected area, regardless of their properties.

This is useful primarily for cropping unwanted areas out of a survey.

Parameters: None

Accept All Soundings

"Unrejects" all soundings within the selected area (excluding Additional Soundings).

This clears any filtering, undoes any manual rejection and potentially ignores blocking.

Parameters: None

Accept or Reject Additional Soundings

Accepts or rejects all Additional Soundings within the selected area.

Additional Soundings are soundings that some echosounders report above and beyond the usual number provided by their bottom detection algorithms. For Kongsberg Maritime echosounders, these are call Extra Detections. For Teledyne-Reson echosounders, these are called Multi-Detect.

Parameters:

  • Action

Accept Only Specified Frequency

Rejects all soundings that were acquired by a frequency different than the specified frequency.  When acquiring bathymetry with multi-frequency sonars such as the R2Sonic multi-spectral sonar, it allows the user to generate a surface using only a specific frequency.  The user must use the Revert All Filtering or Clear Flags with Filter option to reset the soundings before performing another use of this filter on a different frequency.  This filter is for advanced users and knowledge of the sonar frequencies needs to be known in advance.

Parameters:

  • Frequency to Accept

Respect or Ignore All QINSy Blocking

Rejects or accepts soundings by respecting or ignoring the original QINSy blocking flags.

Any sounding with a blocking flag set will be rejected, unless blocking flags are being ignored (or it has been manually accepted).

Parameters:

  • Blocking Flags

Respect Individual QINSy Blocking Flag

Rejects soundings by respecting a particular online QINSy blocking flag.

Any sounding with the selected blocking flag set will be rejected.

Parameters:

  • Flag

Set Flags

Sets any of the flags Plotted, Feature, or Suspect for the soundings.

Parameters:

  • Set Plotted Flag
  • Set Feature Flag
  • Set Suspect Flag

Clear Flags

Clears the specified data status flags for all soundings.

Clearing the Manual Edit flag or Filtered flag may cause rejected soundings to become accepted, if no other reason remains for rejecting them.

Parameters:

  • Clear Manual Edits
  • Clear Filtered Flag
  • Clear Feature Flag
  • Clear Plotted Flag
  • Clear Suspect Flag

Apply Refraction Correction

Applies an empirical refraction correction based on a simplified refraction model which introduces a sound speed correction at a specified depth level.  The idea is to define a 'Refractor' plane below the MBE transducer which delineates the depth at which the refraction correction is applied to the SV profile used during acquisition. When you set a depth of 10 meters, it means that all the depths below 10 meters are affected by the refraction correction. No refraction corrections are applied to depths that are above the specified refractor depth.  The following diagram illustrates the basic premise of the filter. The filter can be applied to 'Rejected/Flagged' soundings using the 'Filter Rejected' option. If this option is set to 'No' on 'Accepted' soundings will be filtered. 

The refraction correction is stored separately from the corrected sounding and can be reset with the "Restore Raw Data" filter.

Parameters:

  • Refractor Depth
  • Sound Velocity Correction
  • Filter Rejected

Z Shift Data

Applies the specified shift to all soundings, moving them in the Z direction.

The shift is stored separately from the corrected sounding and can be reset with the "Restore Raw Data" filter.

Parameters:

  • Z Shift

Restore Raw Data

Re-enables all soundings disabled by manual editing and filtering and re-disables soundings that were previously blocked but then later re-accepted through manual editing. Can also reset the custom XYZ shift that may have been applied with the Z-Shift filter or the Refraction Correction filter.

Parameters:

  • Reenable Disabled Soundings
  • Reset XYZ Shift

TIN Decimation

Rejects soundings using a triangulated irregular network (TIN), leaving only those soundings required to capture the shape of the surface.

A coarse TIN is constructed. Triangles are then subdivided by inserting outlier soundings. This process is repeated until no sounding is farther than the tolerances from the mesh. Finally, all soundings which are not part of the TIN are rejected.

Set the Tolerance as % of Depth to zero to disable the relative tolerance.

Reduce the Maximum Link Distance to increase the density of the TIN.

Parameters:

  • Absolute Tolerance
  • Tolerance as % of Depth
  • Maximum Link Distance


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