The Sonar Viewer

The Sonar Viewer contains separate display panels for each available sonar channel, which can be controlled by the sonar control bar and the control panel within each individual display.

3. Toggle sonar channel displays

The sonar is split into a separate display for each available sonar channel, up to a maximum of four channels. The available channels are Primary (1), Secondary (2). Down-scan (DS) and Side-scan (SS). The visibility of each channel can be toggled by clicking the appropriate button in the control bar (initially, all sonar channels are shown).

Layout

The sonar viewer has a flexible layout,

·The relative size of each sonar channel display can be adjusted by dragging the separator bars (1, overlaid in red) using the left mouse button.

·By default, all sonar channels are shown. The visibility and position of individual channels can be controlled using the sonar channel selector panel (2), which is displayed when the mouse pointer is held towards the bottom-right corner of the sonar viewer display.

The sonar channel selector

The sonar channel selector is shown when the mouse pointer is held towards the bottom-right corner of the sonar viewer display and contains buttons for each supported sonar channel; primary, secondary, down-scan and side-scan:

·Each channel that is available in the current file is shown as a small image. Channels that are not present in the current file are shown with grey backgrounds.

·To toggle the visibility of a channel, click the required channel button once using the left mouse button. When a channel is hidden, the button is shown with a faded background, as shown for the side-scan channel in the image above (right).

·To move the position of a channel, drag the channel button to another position within the channel selector (by clicking and holding the left mouse button). When a channel is dragged to a new position, it swaps positions with the channel on to which it was dragged.

Sonar viewer with primary and secondary channels selected

Sonar viewer with only the primary channel selected for display

Controlling the Sonar Display

The current position in the sonar file is shared by all of the channel displays, and can be controlled by using the sonar control bar, as well as by dragging the sonar image within any of the individual sonar channel displays, by using the left mouse button with the mouse in move mode.

Mouse Control

·Zoom channel displays by using the mouse wheel; move the wheel forwards to zoom in, and backwards to zoom out. The sonar display can also be zoomed by drawing a zoom box using the left mouse button, with the mouse mode in zoom mode.

·Move the sonar display by clicking and holding the left mouse button and moving the mouse, with the mouse in move mode (or use the middle mouse button, if available, whilst in any mouse mode). When moving forwards or backwards in the sonar file, all channel displays are moved together.

·Double-click the left mouse button with a channel display to force the sonar limits to fit the current display size.

·Measuring distance and estimating object height (side-scan view only) can be performed with the mouse in measure mode. See Mouse Control for more details.

·Waypoints can be dropped in any position in any of the sonar viewers, either via the right mouse button menu or by using the left mouse button with the mouse in drop waypoint mode. Waypoints dropped within primary, secondary and down-scan channels will appear along the sonar track, whilst waypoints dropped within the side-scan display will be located according to their distance and bearing from the current sonar location.

Sonar Channel Control Panels

Individual settings for sonar channel displays, such as brightness, contrast and the colour palette, are set via the sonar channel control panel:

Each channel display has a separate control panel (2) that is displayed when the mouse pointer is held towards the bottom left corner of the channel display (1).

Options within the sonar channel control panel vary, depending on what type of sonar channel is being displayed:

Primary, Secondary and Down-scan Control Panels

1, 2. Brightness, Contrast

Brightness and contrast can be adjusted using the sliders.

3. Palette

Select the colour palette for the channel using the drop-down palette list.

4. Horizontal zoom

Horizontal zoom affects the length of the sonar track that is shown in the channel display. Move the slider to the right to zoom in (show a smaller time period), and to the left the show more of the track at the same time.

5. 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 have a small, but noticeable effect on the remaining sonar image.

Primary sonar channel showing noise from interference

Primary sonar channel with x1 noise reduction

The Side-scan Control Panel

The side-scan sonar display includes an extra option, auto-gain (1), which adjusts side-scan signal returns to increase brightness at the edge of the side-scan swath. The amount of auto-gain applied to the side-scan display can be adjusted using the slider; move the slider all the way to the left to remove auto-gain, and all the way to the right for full auto-gain.

Vertical zoom (2) works in the same way as horizontal zoom for the other sonar channels (see above).