Sidescan Track Review
Sidescan track review extends the existing track edit window to display in-place sidescan sonar imagery for any track that contains sidescan data.
The track edit window provides a convenient and fast way to review sidescan sonar imagery from a single sonar log and perform actions such as marking waypoints on underwater structure, exporting selected regions as high-resolution images, and selecting regions of sidescan to be added to a sidescan mosaic.
Displaying Sidescan in the Track Edit Window
·Open a track for editing.
·If the selected has track has associated side-scan data, the Show Sidescan button will be enabled (circled).
·Clicking the Show Sidescan button will replace the depth point view with the sidescan view (click the Show Sidescan button again to revert the track display to the track-point view).
·Sidescan imagery is displayed in place of track-points, the sidescan menu panel is displayed in the track menu bar and the sidescan swath control is shown at the bottom of the map view:
Controlling the sidescan display
By default, the entire sidescan swath is selected for display and can be viewed by simply panning and zooming the map area.
The displayed sidescan can be controlled in a number of ways:
·Start and end positions can be adjusted to limit the length of the displayed swath.
·Port and starboard ranges can be adjusted to limit the width of the swath. Both the upper and lower ranges for each swath side can be adjusted.
·The palettes, brightness and contrast, auto-gain, noise-reduction and sharpening can all be adjusted.
·The opacity (transparency) of the swath can be adjusted.
Swath start and end positions
Swath start and end positions can be controlled using the sidescan swath control bar, located at the bottom of the track edit window:
The Sidescan Swath Control
The start and end positions of the displayed swath can be adjusted by dragging the sliders (1) with the left mouse button held down. When the displayed range is less than the full range of the track, the entire displayed range can be moved by dragging the range bar (2). Clicking in the areas to the left or right of the range bar will move the entire range by a small amount towards the direction of the click. To reset the range to full, click the Full Range button to the right of the toolbar (3).
The Sidescan Menu Panel
All sidescan properties, other than the swath limits described above, are available in the Sidescan Menu Panel which is displayed as part of the track menu bar when sidescan is being displayed.
1. Swap Sides
Click this button to swap the sidescan port and starboard channels. This function is useful when a unit has been misconfigured whilst recording and needs to be corrected. Note that changes made to channel arrangement in the track will be reflected in any sidescan mosaics in which the track is used.
2. Use Headings
Accurate headings can significantly improve the geo-location of sidescan imagery when available. By default, headings will be used if they have been recorded as part of the sonar log. If the recorded headings are of poor quality, this button can be used to revert to using the track course when locating sidescan imagery.
The palette for the sidescan display can be chosen from the drop-down palette selector.
1. Signal Display
The signal display affects which sonar return signal is displayed when sidescan swathes overlap.
In the track display, signal display can be on of:
Display the signal return that is closest to the transducer. This usually results in the best image quality, as signal quality degrades with distance.
Display the signal that is latest in time.
Display the signal that is earliest in time.
2. Noise reduction
Noise reduction can help in reducing the effects of interference on the sonar image. To enable noise reduction, check the Noise Reduction check-box. Noise reduction is available in two versions; x1 and x2, where x1 provides basic noise reduction suitable for most sonar recordings, and x2 provides a more aggressive form of noise reduction that may be useful for particularly noisy sonar logs. Note that the x2 noise reduction variant may result in some loss of image detail.
The sharpening tool uses hardware accelerated image process techniques to increase image sharpness and local contrast. The degree of sharpening applied can be varied by used the slider.
The auto-gain function evens out the signal return across the full sonar range. This can reveal details at the edges of the sonar range that would otherwise be hard to see. See the sonar viewer manual page for more information. The impact of auto-gain can be adjusted from 0 (none) to 1 (full) by using the slider.
5/6. Port and Starboard range
The upper and lower limits for the port and starboard sonar can be adjusted by using the port and starboard range sliders.The port and starboard range sliders work in a similar way to the swath position slider described above; either edge of the slider can be adjusted independently to move the upper or lower range, and the whole range can be moved by dragging the centre of the range slider. The range can be restored to its full extent by clicking the Full Range button to the right of the slider.
Playback using the sonar viewer
During sonar playback, the screen remains centred on the current sonar position if the Show Boat Position option has been selected in the sonar viewer. We can use this feature to review sidescan data in a track:
·Open the sonar viewer panel by clicking the Show Sonar button.
·Ensure that the full sidescan swath is visible by clicking the Full Range button at the right of the Sidescan Swath Control.
·Start playback of the sonar recording. The sonar recording will commence playback, and the track view will update to keep the current sonar position in the centre of the screen.
·The position of the playback can be adjusted at any time, either by dragging the sonar position slider, or grabbing the sonar image in the sonar viewer with the mouse in Pan mode (see the sonar viewer manual pages for more information). Adjusting the position of the sonar in this way will also update the position in the track edit area.
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