Fig. 1 - Description of visualizing 2D DFSU in QGIS
#02 - Add results to the Map - see Fig. 2
If the installation has been carried out correctly, dfsu files will be recognised as meshes in the browser and are marked with an appropriate icon. Add the mesh to the map using the usual methods in QGIS, for example by double-clicking the mesh.
Fig. 2 - Loading feature shapefiles into QGIS
#03 - Configure result display - see Fig. 3
It is easier if you start with a mesh that contains only one single timestamp, for example, the maximum values. We explain how to deal with time series further below.
Select layers to be displayed
In the "Layer properties - Symbology" in the leftmost tab, the result types available in the dfsu are listed. Squares mean representation as a surface, some layers can additionally display flow vectors. By clicking on the corresponding icon, a certain result type is activated and highlighted.
Fig. 3 - Adjusting symbology on QGIS.
#04 - Visualise Contour lines – see Fig. 4
The visualization of the surfaces is configured in the second tab from the left.
Fig. 4 - Symbology adjustment in QGIS
Min and Max
"Min" and "Max" are used to set the limits of the colour gradient. The double arrow -restores the minima and maxima from the data set. If you narrow the limits, values outside the limits are displayed with the outermost palette colour.
#05 - Resampling method - see Fig. 5
- None: Each triangle has a specific colour
- Neighbour Average: Interpolation across triangles, multiple colours per triangle
Fig. 5 - Resampling Method
#06 - Interpolation - see Fig. 6
- Discrete: each colour is valid within a class up to the upper limit, i.e. the colours show steps
- Linear: each colour is valid only for a certain value, linear interpolation in between the colours
- Exact: each value in the mesh receives its own colour; this would probably only make sense for discrete values
Fig. 6 - Discrete Interpolation vs Liner Interpolation
Both figures above were created using the "Neighbour Average" resampling method, which means that the colours are interpolated across the mesh elements. On the left you see the interpolation "Discrete" with one colours per class. On the right the interpolation is "Linear", which has no classes, but only interpolation points for individual colours, between which the colours change stepless.
- Continuous: automatically 52 values; optically, this method blurs the steps
- Equal Interval: Number of classes can be defined; the values of the upper class limit (for "Discrete") or the supporting points (for "Linear") can be adjusted individually
#07 - Vector visualisation - see Fig. 7
The symbology of vectors is only accessible if an arrow symbol is activated under the layers to be displayed (see above), typically for flow velocity over time. The arrows can be coloured, scaled, and displayed either on each mesh element or in a specific grid.
Fig. 7 - Symbology edition in QGIS
#08 – Display mesh elements - see Fig. 8
Fig. 8 - Mesh symbology edition
#09 – Control timeline - see Fig. 9 - Fig. 11
Layers that have multiple time steps are marked with a small clock icon.
Fig. 9 - Add layers in QGIS
In the "Layer Properties - Source" you may fix the layer to a certain time step. This switch is also interesting because here you can see the original time steps of the dfsu file.
Fig. 10 - Time step setting in Layers Properties
In the "Layer Properties - Temporal" you see under "Start time" and "End time" the period covered by the dfsu file. The "Reference Time" does not need to be changed because result files created with MIKE+ contain absolute time information anyway. Time display is controlled via the Temporal Controller Panel, which you activate via the menu View " Panels " Temporal Controller.
Fig. 11 - Temporal Controller
Use the controller is self-explanatory. Note that the period displayed does not automatically coincide with the dfsu file. If you do not see the desired result, perhaps you are displaying the wrong time period. Copy the time specification from the "Temporal" tab.
#10 - Query results - see Fig. 12
Retrieve results in individual mesh elements with the "Identify" tool by clicking on a specific cell.
Fig. 12 - Identifier Tool
#11 -Plot time series - see Fig. 13 - Fig. 15
Open the time series plot by right-clicking on a layer and selecting "2D Plot":
Fig. 13 - Accessing Time Series plots through 2D Plot
The 2D plot has the following parameters:
- Layer: dfsu file to be displayed
- Plot: select "Time-series"
- Group: result type to be displayed within the dfsu file
- From Map: select "Point
Fig. 14 - Crayfish 2D Plots
The time series display is interactive. If you move the mouse over the map, the plot changes. If you do not see any crosshairs, select again "From Map: Point". With a <Click> you select a specific point. With <Ctrl> + <Click> you select several points.
Fig.15 - 2D Plot Dynamic View
Export the plot in various image formats and as CSV by right clicking on the 2D plot.
#12 - Display longitudinal profile - see Fig. 16 - Fig. 18
Open the longitudinal profile by right-clicking on a layer and selecting "2D Plot":
Fig.16 - Accessing the 2D Plot option
The 2D plot has the following parameters:
- Layer: dfsu file to be displayed; apparently only dfsu files with a time axis work
- Plot: select "Cross-section
- Group: result type within the dfsu file
- Time: with "current" the cross-section changes when you adjust the time with the controller
- From Map: no selection option
Fig. 17 - Total Depth Water in Crayfish 2D Plot
To draw the profile path on the map
- click on <From Map>
- click on the map for the starting point
- and for each additional vertex
- and finish with a right mouse click (does not create another vertex!)
The Y-axis is normally scaled automatically, which is annoying when viewed over time. Lock the Y-axis with a right mouse click:
Fig. 18 - Lock the Y-axis
#13 - Display in 3D - see Fig. 19 - Fig. 21
Official QGIS documentation can be found here - QGIS User Guide 11. Visualizing Maps 11.2. 3D Map View
Create a new 3D Map View via the menu "View » 3D Map Views" and open the configuration:
Fig. 19 - 3D Map 1
Select "Mesh" and the desired dfsu file. Adjust the symbology:
Fig. 20 - 3D Configuration Terrain
Press <OK> to display the 3D view. Change the perspective with the mouse buttons or with the four keyboard arrow keys, optionally combined with <Shift>.
Fig. 21 - 3D Map 1
#14 - Derive additional results with the Mesh Calculator - See Fig. 22 - Fig. 23
Official QGIS documentation: https://docs.qgis.org/3.28/en/docs/user_manual/working_with_mesh/mesh_properties.html#mesh-calculator
Find the Mesh Calculator in the "Mesh" menu.2)
Fig. 22 - Additional results derived
The calculated values are visible in the original mesh as additional channels:
Fig. 23 - Additional results derived
#15 - Toolbox for exporting data - see Fig. 24
Official QGIS documentation can be found here - QGIS User Guide 25. Processing providers and algorithms 25.1. QGIS algorithm provider 25.1.7. Mesh
Go to menu "Processing > Toolbox" and locate group "Mesh".
Fig. 24 - Processing Toolbox
#16 - Export contours - see Fig. 25 - Fig. 27
The tool exports:
- contour lines
- polygons: one multipart polygon per class
Fig. 25 - Exporting Contours
Either you specify Increment between contour levels, Minimum contour level and Maximum contour level.
Or you specify the class boundaries List of contours level, in the picture above 0.01,0.2,0.4,0.6,0.8,1,1.5,2,3,999. The smallest and the largest value are understood as outer limits, beyond which no polygons are exported.
Fig. 26 - Contours definitions
This tool converts dfsu files (e.g. results of maximum water depth) into a polygon layer using the non-interpolated mesh triangles.
1) Select the dfsu file to be converted.
2) For the output layer define the coordinate reference system. **
Fig. 27 - Export Mesh Faces
** Please note that sometimes the tool refuses to export without CRS.
#16 - Export Mesh Edges and Export Mesh Vertices
Those tools do not work with dfsu files, because dfsu files do not contain edges or vertices, only faces.
#17 - Export animations - see Fig. 28
Fig. 28 - Export Animations
* not to be confused with a different Mesh Calculator in the Processing Toolbox under group "Crayfish"
FURTHER INFORMATION & USEFUL LINKS
Manuals and User Guides
QGIS User Guide 11. Visualizing Maps 11.2. 3D Map View
QGIS User Guide 17. Working with Mesh Data
QGIS User Guide 25. Processing providers and algorithms 25.1. QGIS algorithm provider 25.1.7. Mesh
MDAL and QGIS Mesh Layer - Lutra Consulting
Overview of QGIS 3.12 Mesh Features - Lutra Consulting
Visualise 2D DFSU in QGIS 3.18 & 3.20
Download relevant files here