The Sonar Viewer

The sonar viewer is part of the Track edit window, and displays sonar recordings for tracks that have been imported from compatible sonar log files. All available channels can be viewed, either together or separately, and recordings can be replayed at speeds of up to 30x.

ReefMaster IDX sonar index files

To improve performance when displaying sidescan mosaics and sonar logs, ReefMaster creates a new sonar log index file in the same location as the existing log file. The disk location for the sonar log file must be writeable, so that ReefMaster can create this file. The index file is created when a track is first opened for editing, and the sonar and sidescan mosaic buttons will not become enabled until the index file has been created.

Using the Sonar Viewer

If sonar data is available for viewing, the Sonar Viewer button in the track menu bar will be enabled:

To open the sonar viewer display, click the Sonar Viewer button. If the sonar button is disabled, then there is no compatible sonar recording associated with the track.

The sonar viewer display consists of display areas for each sonar channel and a sonar control bar.

The Sonar Control Toolbar

The sonar control bar is used to control sonar playback and the current position within the sonar log.

1. Image snapshot

To take an image snapshot, click the Image Snapshot button. Images can either be saved to a file (high quality JPG) or copied to the clipboard, from where they can be pasted into other applications, such as a word processor or email. A data panel containing position and depth information can also be included by checking the Include Data Panel option.

2. Show Boat Position

Click the boat button to show the current position in the track as a boat icon within the map view. When the boat position is shown, the map view will stay centred on the current position. This option can be useful when used in conjunction with a sidescan overlay in the map view.

3. Show or hide Depth Scales

Use this toggle button to show or hide the depth scale on all of the sonar channel displays.

4. Sonar Playback Controls

The playback controls are used to control sonar playback. Start playback by using the Play button and stop playback using the Stop button. Use the slider (5) to adjust playback speed between 1 and 30 x.

The current time position within the sonar recording is shown. This position relates to the most recently displayed sonar ping, in the same way that a boat's position relates to the sonar pings that are currently being received. For 2D sonar, this is the right hand edge of the display and, for side-scan, the top edge.

6. Position scroll bar control

Drag the position scroll bar to move the displayed position within the sonar log. Note that all channels move together.

Sonar Channel Displays

Each sonar channel is displayed in a separate window within the sonar viewer display:

Settings for each channel can be accessed in the channel settings toolbar, which can be displayed by holding the mouse pointer towards the lower-left corner of each sonar display panel:

Per-channel sonar display settings

The settings panel contains a range of controls to adjust the sonar image:

1. Brightness and Contrast

Brightness and contrast can be adjusted using the sliders.

2. Sharpening

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.

3. Auto-gain (sidescan only)

Auto-gain 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 completely, and all the way to the right for full auto-gain.

4. Palette

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

5. Zoom

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. Use the mouse-wheel to zoom in to view a smaller depth range, and double-click with the mouse anywhere in the sonar display to reset limits to the current depth range.

6. 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.

7. Sonar range limits

Use the range slider to adjust the upper and lower depth range of the displayed image. The range itself can be moved by dragging the centre of the range bar. Note that this control is shown vertically, and to the right of the control panel, for 2D sonar channels.

The sonar channel selector

By default, all available sonar channels are displayed when the sonar viewer is first opened. The visibility and relative position of each channel can be adjusted by using 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.

Measuring Distance and Estimating Object Height

Measuring Distance

With the mouse in measure mode, distances can be measured within any sonar channel display by holding down the left mouse button and moving the mouse over the required area:

Measuring height

In sidescan channels only, the height of an object can be estimated by measuring its shadow.

To estimate an object height, click and hold the right mouse button and draw a line for the full length of the object shadow. The mouse must be in measure mode to perform this operation:

This tree stump is approximately 1.9m high

The measure height tool can also be used to estimate the depth of objects within the water column (e.g. fish). In this case, the tool should be extended from the object to the shadow cast by the object. The height shown will be the height of the object from the bottom, and the depth of the object can be calculated by subtracting that height from the current depth.

Correcting Track Point depths

The depths of existing points within the track can be corrected by redrawing them over the observed bottom in a 2D sonar channel display.

To redraw depths, click the Correct Depths button in the track toolbar:

Track-points from the associated track are displayed within each 2D sonar channel display (all channels except sidescan). The position of the track-point within the sonar display reflects the depth of the track-point as calculated by the originating sonar unit.

If the depth is incorrect with respect to the displayed bottom, track-points can be redrawn by clicking and holding the left mouse button and drawing along the visible bottom line:

Once depths have been corrected, the udpated track-points must be saved by clciking the Save button at the top-right of the sonar display. Changes can be discarded by clicking Cancel:

Note that for Humminbird sonar logs, it is important that the water salinity and temperature have been set correctly during the import process. If these parameters have not been set correctly, track-points may be shown at incorrect depths within the sonar display. See GPS Equipment Profiles.