3. Create the graphical model for stream delineation

3.1. Mosaic SRTM tiles

The first step is to mosaic the SRTM tiles.

We would like to offer the user the choise to select several tiles at once as input.

1. In the Inputs panel double click on .

2. In the Multiple Input Parameter Definition write DEM Tiles as Description and choose Raster as Allowed layer type. Keep Mandatory checked and click OK.

In this way the user has to select a set of raster layers before the model can run.

3. Switch to the Algorithms panel by clicking on the tab.

4. Search for Build virtual raster and double click on the tool.

5. In the Build virtual raster dialogue replace the text at Description with Mosaic DEM Tiles.

6. Click at Input layers and select DEM Tiles. Click to go back.

7. Change Place each input file into a separate band to No, because we don't want to stack the layers. Check if the dialogue looks like the figure below.

8. Click OK.

Note that we only provide the output names in these tools if the output is a final result. In our case the mosaic is a temporary result.

Now the screen should look like this:

Let's add the next process.