Generate and display a depth matrix

In Hydromagic, a matrix is a collection of regularly spaced depths, which can be projected over the map as color or text. Such data is also referred to as a digital terrain model or DTM. A matrix can be used to view a 3D model of the terrain using the "3D Terrain Viewer", in volume calculations or to generate depth contours.

During the generation of a matrix from a sounding, the scattered data points are converted to regularly spaced data using a TIN (Triangulated Irregularly Network). This TIN is generated using a Delaunay triangulation algorithm. All new data points are generated by "filling" the triangles, which have been formed from the scattered data. The image below shows a color matrix which has been generated using TIN (data points at 0.25 meter interval).

Example matrix generated from sounding and boundary data.

Generating a matrix

To generate a matrix, you must have either a valid sounding or a shoreline containing depth information loaded into your project. Without the sounding or shoreline data it is not possible to generate a matrix. Use the "Generate sounding wizard" to generate sounding(s) from your raw data file(s) first.

In order to generate the matrix, you have to specify some settings, like the data being used to generate the matrix, as well as some output options. To do so, open the 'Generate Matrix' dialog by selecting the 'Generate Matrix...' option from the 'Tools' menu:

Use the 'Generate Matrix' utility to generate a matrix using a TIN algorithm.

Sounding data

Select which sounding(s) you wish to use to generate the matrix. By clicking the "Select..." button, you will be able to select one or more soundings that will be used to calculate the triangulation from which the matrix or digital terrain model will be generated.

Select which sounding(s) to include in the
matrix generation by checking boxes.

Boundaries

In Hydromagic, boundaries can be used to define a shoreline, a clipping area, or an island. When a boundary is defined as a shoreline, including the boundary will automatically include the data points defined on this line.

When an island or clipping boundary is selected, it will determine which areas should be filled with data and which should not. This can be used in cases when only a part of the sounding areas has to be interpolated. When no boundary has been selected, the data points of the selected soundings will be used to determine the area that needs to be filed with data.

Select which boundaries to include in the
matrix generation by checking boxes.

Sounding channel

You can use this setting to select which data of the sounding is used to generate the matrix. This can be one of the following values:

• Depth recorded with the low frequency channel of your echo sounder;
• Depth recorded with the high frequency channel of your echo sounder;
• Elevation recorded with the low frequency channel of your echo sounder;
• Elevation recorded with the high frequency channel of your echo sounder;
• The difference in depth between the high and low frequency channel (Low - High);
• The difference in depth between the high and low frequency channel (High - Low);
• Bottom loss (low frequency);
• Bottom loss (high frequency);
• Bottom reflection (low frequency);
• Bottom reflection (high frequency);
• Bottom density (low frequency);
• Bottom density (high frequency);
• Bottom porosity (low frequency);
• Bottom porosity (high frequency);
• Sensor data channel 1;
• Sensor data channel 2;
• Sensor data channel 3.

When soundings contain tide information, the "Elevation (Hi Frequency)" option will be selected by default. If you want to generate the matrix using the corrected depth values without tide correction, select the 'Depth (Hi Frequency)' option instead. When the selected soundings don't contain tide information, the "Depth (Hi Frequency)" is selected by default.

Please note that information on bottom loss, reflection, density and porosity will only be available on certain types of echo sounders. The sensor data channels can be used to store for instance magnetometer or temperature data.

Select the data source for the matrix cells from the drop down selection.

Matrix spacing

You can select the spacing of the regularly spaced data here. The same spacing is applied to both the X and Y axis. The spacing must be entered in the same units used for the map projection.

Which spacing to use, depends on the zoom scale you are using. For an overview of a large area, you can use 2.5 meter. When zooming in on a smaller area, the best is to use values between 0.25 and 1.00 meter.

Please note that when using a larger spacing, it will be generated and displayed faster than a denser matrix.

Output file name

Enter the name of the generated file here. This setting is required. Use the browse button to select the output folder and file name. The data will be added to the current project and stored in a separate ASCII XYZ file at the desired location.

Generating the matrix

Finally, click the "OK" button to start the process. It should take a couple of seconds; you can watch the progress in the status bar of the main window.

After generation, you will notice the matrix has been added to the project. Depending on the configuration, the newly generated matrix will be drawn over the map.

Displaying the matrix

There are more ways of showing the matrix on the map. In the example near the top of this page, it is displayed as both colors and text at a 5x5 meter interval. It is also possible to not show it (and just use the matrix to export data), to show it with colors only (using the defined color ranges) or to show its depths as text.

To change settings on how the matrix is shown, right-click the 'Matrices' folder in the 'Project Explorer' and select the 'Display Options...' option from the pop-up menu. A dialog with all matrix settings will be displayed. It should look like the screen shot below:

The matrix display can be customized.

Display as colors

The first section is to enable or disable the color overlay, and to specify which colors to use for the different depths. When checking the "Display matrix as colors" option, the matrix is displayed as colors on the map. The "Colors..." button will also be enabled, so you can start creating the color ranges for your sounding.

After clicking the 'Colors...' button, the following dialog will appear:

In this dialog, you will be able to add, remove or modify color ranges by clicking one of the buttons at the bottom of the list. To change a range, double-click on it and adjust the settings.

In case you want to store the color scheme you designed for other projects, you can store it in a separate XML file using the "Save..." button. Just use the "Load..." button in the other project to retrieve this scheme.

It is also possible to create a color scheme using a min, max and step value. To do so, select the 'Auto...' button, then select the lower and upper range, and specify the interval between the ranges.

This tool will generate max 30 ranges, so it is important to choose the correct interval.

You can click the magnifier glass buttons to detect the minimum and maximum values used in all the generated soundings together.

Display color legend

The color dialog also contains settings for the color legend, which can be displayed as a map overlay when colors are displayed. You can turn it on or off here, and select the location where it is displayed.

Display depth as text

Using the 'Display matrix as depths' checkbox, you can enable and disable depths in text. Depending on the size of the spacing used to generate the matrix, you need to adjust the text intervals so that the text on the map does not intersect.

Video tutorial

This video tutorial shows how to generate a matrix from sounding(s) and shoreline(s).