In this tutorial, we will learn how to clip a raster file using VOSWMM. To follow along, you will need a DEM layer to be clipped and a polygon shape file to define the clipping area.
Step 1: Download the DEM File To begin.
Step 2: Adding the DEM File
Open VOSWMM and navigate to the “GIS Tools” menu. Click on “Add Layer” to import the DEM file.
Select the downloaded DEM file from your computer to add it to the map.
Step 3: Zooming to the Imported Layer
To visualize the imported DEM file, extend the “Imported” layer in the “Map” tab. Right-click on the imported DEM file and select “Zoom to Layer” to focus on the imported file.
Step 4: Creating the Polygon Layer
To define the area for clipping the DEM file, we need a polygon shape file. In this exercise, we will create a new polygon layer.
Click on “Create Polygon Layer” in the software. Save the shape file to your desired location.
Step 5: Drawing the Polygon
Left-click on the desired locations on the map to create the vertexes of the polygon. Continue left-clicking to add more vertexes and shape the polygon according to your requirements.
To complete the polygon drawing and access the context menu, right-click on the map. You will have four options for managing the shape file:
- Delete Sketch: Use this option to delete the current sketch and start over.
- Finish Sketch: Selecting this option finalizes the sketch and adds the created shape file under the “Imported” layer. Once you finish the sketch, you cannot add more polygons to this layer.
- Remove Last Vertex: This option allows you to remove the last vertex you added. It’s useful if you mistakenly placed a vertex or no longer need the last vertex.
- End Editing: Select this option to end the current shape drawing and start drawing a new shape. It enables you to create different polygons within the same shape layer.
Step 6: Clipping the Raster
After creating the polygon(s), click on “Clip Raster”.
In the opened window, assign the imported DEM file to the “Input Raster” field. Assign the drawn polygon shape file to the “Input Vector” field. Choose a destination to save the clipped file in the “Output Folder” field.
Once you have set the input raster, input vector, and output folder, click on the “Run” button to execute the tool.
Step 7: Viewing the Clipped Raster
The software will process the clipping operation, and the resulting clipped raster will be added as a new layer under the “Imported” layer. Right-click on the clipped raster layer and select “Move Up” to make it visible on the map.
You have successfully clipped a raster file in VOSWMM. You can now utilize the clipped raster for further analysis or visualization within your project.