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    "# Post-processing with QGIS\n",
    "During a hydraulic study, we want to visualize simulations results directly over the study area. This tutorial presents a method for visualizing Watlab simulation results using **QGIS**. \n",
    "## Importing Watlab result files into QGIS\n",
    "For each simulated time step, Watlab generates a `pic_XX_XX.txt` file containing the results, typically stored in a folder named `Output`. These files can be imported into QGIS as point layers.\n",
    "\n",
    "Open QGIS and go to:  `Layer` → `Add Layer` → `Add Delimited Text Layer...`\n",
    "\n",
    "<div align=\"center\">\n",
    "<img src=\"add_texte_delimeted_layer.png\" alt=\"Add text layer\" width=\"600\"/>\n",
    "</div>\n",
    "\n",
    "**Parameters:**\n",
    "  - **File name**: Click the three dots to browse to your `Output` folder and select the `pic_XX_XX.txt` file corresponding to the desired time step.\n",
    "  - **File format**: Choose “Custom delimiter” and select **Tab**.\n",
    "  - **Sample Data**: Make sure the columns are correctly detected (e.g., `x`, `y`, `zb`, `h`, etc.).\n",
    "  - **Geometry definition**:  \n",
    "    - Type: `Point`  \n",
    "    - X field: `x`  \n",
    "    - Y field: `y`  \n",
    "    - Coordinate reference system: `Lambert 72` (EPSG:31370)\n",
    "\n",
    "Once the layer is added, you should see a cloud of points representing the model mesh, one point per cell.\n",
    "\n",
    "\n",
    "## Interpolating results into a raster (TIF File)\n",
    "To visualize the results as a continuous surface, interpolate the point data into a raster.\n",
    "\n",
    "Open the **Processing Toolbox**:  \n",
    "`Processing Toolbox` → `TIN Interpolation`\n",
    "\n",
    "**Parameters:**\n",
    "- **Vector layer**: Select the `pic` layer imported earlier.\n",
    "- **Interpolation attribute**: Choose `h_zb`, click the `+` to add it.\n",
    "- **Interpolation method**: `Linear`\n",
    "- **Extent**: Use the extent of the `pic` layer.\n",
    "- **Pixel size**: Set according to the desired resolution.\n",
    "\n",
    "Give the TIF file a clear name to identify the time step and variable. In the layer properties, adjust the symbology for optimal readability.\n",
    "\n",
    "💡 *To produce high-quality visual outputs, QGIS also allows you to design map layouts with legends, titles, and scale bars using `Project` → `New Print Layout`. This is ideal for exporting clean figures for reports or presentations.*\n",
    "\n",
    "## Elevation profile\n",
    "To represent water surface elevation relative to terrain, you need to combine the water depth `h` with the terrain elevation `zb` from the model. This allows you to create **elevation profiles**.\n",
    "\n",
    "First, add a new column `h_zb` to the attribute table of your result file.\n",
    "\n",
    "1. Open the **attribute table** of the `pic_XX_XX.txt` layer (right-click on the layer → Open Attribute Table).\n",
    "2. Open the **Field Calculator**:\n",
    "    - Create a new field\n",
    "    - Name: `h_zb`\n",
    "    - Output file type: `Decimal (double)`\n",
    "    - Expression:\n",
    "      ```\n",
    "      \"h\" + \"zb\"\n",
    "      ```\n",
    "3. Apply the calculation.\n",
    "\n",
    "\n",
    "  <div align=\"center\">\n",
    "  <img src=\"Attribut_table.png\" alt=\"Attribut table\" width=\"600\"/>\n",
    "  </div>\n",
    "\n",
    "Next, re-interpolate the results using `TIN interpolation`, this time using the `h_zb` attribute.\n",
    "\n",
    "To generate a terrain profile, you can use the `Profile Tool` plugin. This allows you to draw a temporary line directly on the map or use a predefined shapefile if you want to consistently apply the same cross-section across different datasets.\n",
    "\n",
    "Once the raster is generated, you can compare the interpolated water level with your DEM to produce elevation profiles at a specific time step.\n",
    "\n",
    "<div align=\"center\">\n",
    "<img src=\"terrain_profile.png\" alt=\"Terrain Profile\" width=\"600\"/>\n",
    "</div>\n",
    "\n",
    "The picture below illustrates a typical elevation profile:\n",
    "\n",
    "- **Red curve**: Digital Elevation Model (DEM), representing the terrain.\n",
    "- **Blue curve**: Water surface elevation (`h + zb`), showing the simulated water level.\n",
    "\n",
    "💡 *You can export the data (right-click → Export) and make beautiful plots using Python libraries.*\n",
    "\n",
    "<div align=\"center\">\n",
    "<img src=\"elevation_profile.png\" alt=\"elevation_profile\" width=\"600\"/>\n",
    "</div>\n",
    "\n"
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