MODEL DSS

A QGIS Decision Support Tool to demonstrate the use of NEANIAS Project Underwater Services. The purpose of this tool is to support the operation of underwater cable design.

The tool uses several datasets as inputs of the process. Among them are bathymetry and seabed classification. You can donload these data from the NEANIAS Underwater Services or use your own data.

  • The NEANIAS Bathymetry Mapping from Acoustic Data service delivers an advanced user-friendly, cloud-based version of the popular open source MB-System software for post-processing bathymetry.

  • The NEANIAS Seafloor Mosaicing from Optical Data service provides an operational solution for large area representation of the, predominantly flat, seafloor.

  • The NEANIAS Seabed Classification from Multispectral, Multibeam Data service delivers a user-friendly cloud-based solution integrating cutting-edge machine learning frameworks for mapping several seabed classes.

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Model Architecture

Part 1: Working with Restricted areas

Process flow:

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Figure 1: DSS model process flow diagram for restricted areas

Inputs:

  1. Seagrass Vector: Type Vector Layer. A vector layer with seagrass area polygons.

  2. Archeological sites: Type Vector Layer. A vector layer with the location of Archeological areas.

  3. Projected CRS: Type CRS. The projection of the output datasets. A projected CRS should be selected and not a geographic CRS, like EPSG 3857.

  4. Buffer radius: Type Number. The radius of the buffer that will be applied around seagrass areas. Expressed in meters.

  5. Raster analysis cell size: Type Number. The cell size of the produced raster. Expressed in meters.

  6. Raster analysis processing extent. Type Extent. The processing extent for the raster analysis.

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Figure 2: Map of seagrass areas

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Figure 3: Map of underwater archeological areas

Processing algorithms:

  1. Reproject. Reproject the seagrass layer provided by the user to the selected CRS.

  2. Buffer. Apply a buffer to the reprojected vector layer produced from the previous algorithm.

  3. Merge Vector Layers. Merge the Archeological Areas with the output of the previous process in on e single dataset with the restricted areas.

  4. Set style (Restricted Areas). Applies a QGIS style to the derived Restricted areas layer.

  5. Rasterize. Rasterize the vector layer produced in previous step.

Outputs:

  1. Seagrass buffer vector

  2. Restricted areas vector

  3. Restricted areas raster

Part 2: Working with Bathymetry

Process flow:

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Figure 4: DSS model process flow diagram for bathymetry

Inputs:

  1. Bathymetry raster: Type Raster Layer. The input bathymetry dataset.

  2. Bathymetry matrix: Type Matrix. A table that defines the bathymetry categories using min / max bathymetry values for each bathymetry class.

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Figure 5: Bathymetry map

Processing algorithms:

  1. Raster calculator. Applies a land mask to the bathymetry layer by filtering values above zero.

  2. Slope. Calculates the slope raster from the dataset derived from the land mask to the bathymetry raster dataset.

  3. Terrain ruggedness index (TRI). Calculates the terrain ruggedness index from the dataset derived from the land mask to the bathymetry raster dataset.

  4. Hillshade. Calculates a hillshade raster (3D effect) from the dataset derived from the land mask to the bathymetry raster dataset.

  5. Reclassify bathymetry by table. Reclassifies the original bathymetry raster using the classes defined in the bathymetry matrix in order to produce a simplified raster with just a few bathymetry level classes.

  6. Slope histogram. Calculates a histogram for the slope raster layer.

  7. Set style (slope). Applies a QGIS style to the derived slope layer.

  8. Set style (TRI). Applies a QGIS style to the derived TRI layer.

  9. Set style (hillshade). Applies a QGIS style to the derived hillshade layer.

  10. Set style (classified bathymetry). Applies a QGIS style to the derived classified bathymetry layer.

Outputs:

  1. Slope raster layer

  2. TRI raster layer

  3. Hillshade raster layer

  4. Classified bathymetry raster layer

  5. Slope histogram web page with interactive plot

Part 3: Working with cable layer

Process flow:

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Figure 6: DSS model process flow diagram for underwater cable dataset

Inputs:

  1. Bathymetry raster: Type Raster Layer. The input bathymetry dataset.

  2. Seabed classification raster: Type Raster Layer. The input seabed classification raster dataset.

  3. Cable route: Type vector Layer. A vector (line) dataset with a proposed route for the underwater cable.

  4. Slope: Type Raster Layer. Output of the process above.

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Figure 7: Map of proposed undewater cable

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Figure 8: Map of seabed classification

Processing algorithms:

  1. Profiles from lines. Calculates a sampling point dataset along the cable line. For each point it calculates the depth and the slope from the input raster layers.

  2. Profiles from lines (seabed). Calculates a sampling point dataset along the cable line. For each point it calculates the seabed classification from the input raster layer.

  3. Bathymetry scatter plot. Calculates a scatter plot from the sampling point dataset using the distance from the beginning as X and the depth as Y.

  4. Slope scatter plot. Calculates a scatter plot from the sampling point dataset using the distance from the beginning as X and the slope as Y.

  5. Seabed scatter plot. Calculates a scatter plot from the sampling point dataset using the distance from the beginning as X and the seabed category code as Y.

Outputs:

  1. Points along line vector layer

  2. Bathymetry scatter plot web page with interactive plot

  3. Slope scatter plot web page with interactive plot

  4. Seabed classification scatter plot web page with interactive plot

User Interface

The plugin can be accessed from the Processing Toolbox in QGIS. It is available under the NEANIAS tools provider, under the Underwater models group.

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The UI of the SeaDSS tool is presented in the image below:

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Figure 9: The UI of the model

In the left side of the form are the input / output parameters. Input parameters should be provided in order for the model to run. Depending on the type of the parameter the users can select layers that already available in the QGIS map canvas, open a geospatial dataset from the disk, provide a direct input, or use the map canvas to provide the input. Some examples are presented in the images below:

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Figure 10: Layer selection from the available layers in QGIS map canvas

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Figure 11: Interface for tabular (matrix) data entry

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Figure 12: The Coordinate Reference System selection UI

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Figure 13: Extent can be selected from the available in QGIS layers or interactively by drawing on the map canvas

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Figure 14: Outputs can be set as temporary files or permanent files saved to disk. The user can also select to be displayed in QGIS map after the execution of the algorithm

In the left side of the form is the help section where a short description of the model is available. The full help is available as a web page by clicking on the help button in the bottom – right side of the form.

The model runs by clicking on the Run button, after the completion of the necessary input parameters.

During the model execution, log messages are displayed in the model log panel. The progress bar presents also the overall progress of the model.

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Figure 15: Monitoring the progress of the model

All datasets produced from the model are added to the map

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Figure 16: Visualization of the results in QGIS after the execution of the model

Results that are available as html files are listed in the Results Viewer.

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Figure 17: Html outputs available in Result Viewer

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Figure 18: Example of an html model output (elevation profile along cable line)