QGIS/C4/DEM-Analysis/English-timed

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Time Narration
00:01 Welcome to this tutorial on DEM Analysis in QGIS.
00:07 In this tutorial, we will learn to,
00:11 Download DEM data from SRTM data website.
00:16 Show Hillshade of DEM.
00:19 Here I am using

Ubuntu Linux OS version 16.04

00:25 QGIS version 2.18 and

A working internet connection.

00:33 To follow this tutorial you should be familiar with QGIS interface.
00:39 To view the prerequisite tutorials in this series, please visit this website.
00:45 Digital Elevation Model or DEM is a raster file.
00:50 It shows elevation data for each raster cell.
00:55 DEMs are used to represent the bare earth terrain.
01:00 The terrain is usually devoid of vegetation and man-made features.
01:06 DEMs are used for calculations and analysis of an area, based on the elevation.
01:14 Let us download DEM data.
01:17 Open the given link in any web browser.
01:21 Shuttle radar topography mission (SRTM) data website opens.
01:27 SRTM data from this website can be downloaded freely.
01:32 On the Download Manager page, the elevation models are arranged into tiles.
01:39 Two options for Tile Size and Format are available.
01:44 We can choose the tile size and format by clicking the radio buttons.
01:50 Scroll down the page to the world map.
01:54 Use + sign on the left corner of the map to zoom in the world map.
02:00 Click on Maharashtra tile.
02:03 Click on Search button located on the top-left corner of the world map.
02:09 Download window opens.
02:12 Scroll down to Description heading.

Click on Download SRTM link at the bottom.

02:20 A dialog-box opens, select Save File option. Click on OK button.
02:29 On my system, zip file downloads to the Downloads folder.
02:34 Extract the contents of the zip file.
02:38 Right-click and select Extract Here option.
02:43 Double-click on the extracted folder.

This is a DEM dataset.

02:50 Here we see many files with different file extensions.
02:55 Close the folder.
02:57 Open the QGIS interface.
03:00 Click on, Layer menu on the menu bar.
03:04 Select Add Layer, from the sub-menu, click on Add Raster Layer option.
03:11 Data source dialog-box opens.
03:14 Navigate to the SRTM folder downloaded from the SRTM website.
03:21 From the contents of the folder, select the file with .tif extension.

Click on Open button.

03:31 On the canvas you will see DEM of the terrain.
03:36 DEM contains all the 3D information about the terrain.
03:41 Each pixel on the raster image represents the average elevation at that location.

This elevation is given in meters.

03:52 Dark pixels represent areas with low altitude.
03:57 Lighter pixels represent areas with high altitude.
04:02 Let us begin the DEM analysis of this map.
04:07 Click on Raster menu on the menu bar.
04:11 Click on Analysis from drop down.

From the sub-menu click on DEM (Terrain models).

04:19 DEM dialog-box opens.
04:22 Input file field has DEM layer as the default selection.
04:28 Click on Select button next to Output file.
04:33 Save the results to.. Dialog-box opens.
04:37 In the dialog-box, name the file as Hillshade.tif.
04:44 I will save it on the Desktop.
04:47 Click on Save button.
04:50 Select Hillshade as Mode option.
04:54 Here by default Hillshade is already selected.
04:59 Check the check-box next to Load into canvas when finished.
05:05 Here by default it is already selected.
05:09 Leave the default settings as such.
05:12 Click on Ok button.
05:15 A pop-up box opens with message Processing Completed.

Click on OK button.

05:22 Click OK button in the Qgis.bin dialog-box.
05:27 Click on Close button on the DEM dialog-box.
05:32 A new layer, Hillshade is now added in the Layers panel.
05:37 On the canvas you will see a raster map in Hillshade mode.
05:42 This map is generated using light and shadow to create a 3D image.
05:48 To make the model more pronounced, we will use Hillshade as an overlay.
05:54 Now we will change the symbology of the original DEM layer.
05:59 Right-click on the srtm layer in the Layers Panel.
06:04 From the context menu select Properties option.
06:09 Layer Properties dialog-box opens.
06:13 Select Style from the left panel.
06:17 Under Band Rendering section, change the Render type to Singleband pseudocolor.
06:24 Under Load minimum/maximum values, click on minimum/maximum radio button.
06:33 Select Linear from Interpolation drop-down.
06:37 This is a default selection here.

From the Color drop-down select Spectral.

06:44 Scroll down.

Select Mode as Continuous from the drop down.

06:50 Click on Classify button.
06:53 5 new color values are created.
06:57 The colors represent values of elevation of raster from lowest to highest.
07:04 Click on Apply button and OK button at the bottom right corner.
07:10 In the Layers panel, disable the Hillshade layer .
07:14 Uncheck the check-box against Hillshade layer.
07:18 Now on the canvas you will see a map in spectral colors.
07:24 The red shaded terrain is least elevated and blue is most elevated.
07:30 Enable the Hillshade layer.
07:33 Open the Layers Properties dialog-box.
07:37 Select Transparency from left panel.
07:41 Set the Global transparency to 50% by dragging the slider.
07:47 Click on Apply button and OK button.
07:51 Zoom in the map.
07:53 On the canvas now we see an enhanced topography of the landscape.
08:00 Let us summarize,
08:03 In this tutorial we have learnt to

Download DEM data from SRTM data website.

08:11 Show Hillshade of DEM.
08:15 Here is the assignment.
08:17 Visualize the terrain using Slope mode for the raster map. Change the symbology for the Slope layer
08:27 Hint: Select the Mode as Slope and use it as overlay.
08:33 Your completed assignment should look as shown here.
08:38 This video summarizes the Spoken Tutorial project. Please download and watch it.
08:45 We conduct workshops using Spoken Tutorials and give certificates.

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08:54 Please post your timed queries on this forum
08:58 The Spoken Tutorial Project is funded by NMEICT, MHRD Government of India.
09:06 This tutorial is contributed by Vaishnavi Honap from college of Engineering Pune,

Snehalatha Kaliappan and Himanshi Karwanje from IIT Bombay.Thank you for joining.

Contributors and Content Editors

PoojaMoolya