User:Abenk

Mosaicking and DEM Creation in QGIS

What is QGIS

QGIS is an open source software available from here that has a multitude of plugins to ensure that the user has the proper tools for their job. In this tutorial the desktop version for Windows will be used.

Data

The data that was used for this tutorial was taken from the USGS website and is derived from interferometric synthetic aperture radar (IFSAR) data. The data is projected in the NAD83 Alaska projection, and the original TIF images are 5 metre rasters found here.

After extracting the data to your working directory, you can add the individual TIF files to QGIS by clicking Layer » Add Layer » Add Raster Layer, or by pressing ctrl+shift+r.

After the unmosaicked TIF files are added to QGIS it will look like this:

Mosaic Process

In order to mosaic the images properly you will open the DEM(Terrain Models) option by clicking Raster » Analysis » DEM(Terrain Models). This window will appear:

After you select the proper files, name your output file, and run the tool you should get a hillshaded DEM.

Conclusion

As the DEM that you created is extremely high resolution, you can preform cursory photo interpretation on it, as many of the moraines are visible in the image. You can also select areas within the DEM to access a histogram to see the elevation, as well as the slope and roughness of the terrain. You can transform the DEM into different types, i.e. slope, aspect, colour relief, terrain ruggedness index, topographic position index, or roughness depending on your uses for the data.