QGIS/C4/DEM-Analysis/English

Visual Cue	Narration
Slide Number 1 Title Slide	Welcome to this tutorial on DEM Analysis in QGIS.
Slide Number 2 Learning Objectives	In this tutorial, we will learn to, Download DEM data from SRTM data website. Show Hillshade of DEM. Clip on area in DEM using the Clipper tool.
Slide Number 3 Learning Objectives	Show Contour lines for the DEM. Mark the highest elevated area on the contour map.
Slide Number 4 System Requirement	Here I am using Ubuntu Linux OS version 16.04 QGIS version 2.18 and A working internet connection.
Slide Number 5 Pre-requisites	To follow this tutorial you should be familiar with QGIS interface. For prerequisite tutorials in the series please visit this website.
Slide Number 6 About DEM Digital Elevation Model or DEM is a raster file. It shows elevation data for each raster cell.	Digital Elevation Model or DEM is a raster file. It shows elevation data for each raster cell.
Slide number 7 About DEM	DEMs are used to represent the bare earth terrain. The terrain is usually devoid of vegetation and man-made features. DEMs are used for calculations and analysis of an area, based on the elevation.
Slide number 8 STRM website Open Firefox/Chrome web browser. Type http://srtm.csi.cgiar.org/srtmdata/	Let us download DEM data. Open the given link in any web browser. http://srtm.csi.cgiar.org/srtmdata
Cursor on SRTM data website. Click on SRTM data tab on top-left corner of the page.	Shuttle radar topography mission (SRTM) data website opens. SRTM data from this website can be downloaded freely.
Cursor on the Download Manager page. Point to Tile Size and Format. Point to radio button.	On the Download Manager page, the elevation models are arranged into tiles. Two options for Tile Size and Format are available. We can choose the tile size and format by clicking the radio buttons.
Scroll down	Scroll down the page to world map.
Cursor on +/- sign on the map.	You can see Grids on the world map. Use + sign on the left corner of the map to zoom in the world map.
Click on the Maharashtra grid.	Click on Maharashtra grid.
Click on Search.	Click on Search button located on the top-left corner of the world map.
Cursor on Download window.	Download window opens.
Scroll down. Click on Download SRTM.	Scroll down to Description heading. Click on Download SRTM link at the bottom.
A dialog-box opens, select Save file option. Click on OK button.	A dialog-box opens, select Save file option. Click on OK button.
Open Downloads folder and point the zip file. (STRM 51_09)	On my system, zip file downloads to the Downloads folder.
Right-click to extract the contents.	Extract the contents of the zip file. Right-click and select Extract Here option.
Double-click to open the folder. Cursor on	Double-click on the extracted folder. This is a DEM dataset. Here we see many files with different file extensions.
Click on close button on the top-left corner.	Close the folder.
Double-click on QGIS icon.	Open the QGIS interface.
Click on layer on the menu bar. Click on add layer. Click on add Raster layer.	Click on, Layer menu on the menu bar. Select Add Layer, from the sub-menu, click on Add Raster Layer option.
Point to Data source manager Raster dialog-box .	Data source dialog-box opens.
Click on Browse. Locate the SRTM folder.	Navigate to the SRTM folder downloaded from the SRTM data website.
From the folder, select the file srtm_53_11.tif Click Open button.	From the contents of the folder, select the file with .tif extension. Click on Open button.
Point to the DEM on canvas.	On the canvas you will see DEM of the terrain. DEM contains all the 3D information about the terrain.
Point to the DEM on canvas. Scroll to zoom in.	Each pixel on the raster image represents the average elevation at that location. This elevation is given in meters.
Point to the DEM on canvas.	Dark pixels represent areas with low altitude. Lighter pixels represent areas with high altitude.
Cursor on canvas	Let us begin the DEM analysis of this map.
Click on the menu item Raster. Select Analysis from drop down. Select DEM (Terrain models).	Click on Raster menu on the menu bar. Click on Analysis from drop down. From the sub-menu click on DEM (Terrain models).
DEM (Terrain models) dialog-box opens.	DEM (Terrain models) dialog-box opens. Input file field has DEM layer as the default selection.
Click on Select in front the Output file.	Click on Select button next to Output file.
Select the raster file to save the results to Dialog-box opens.	Save the results to.. Dialog-box opens.
In the File name text box, type Hillshade.tif . Click on Save.	In the dialog-box, name the file as Hillshade.tif. I will save it on the Desktop. Click on Save button.
Cursor on DEM (Terrain models) dialog-box.	Select Hillshade as Mode option. Here by default Hillshade is already selected.
Check the box next to Load into canvas when finished.	Check the check-box next to Load into canvas when finished. Here by default it is already selected. Leave the default settings as such.
Click on Ok	Click on Ok button.
Finished dialog-box opens. Click on Ok.	A pop-up box opens with message Processing Completed. Click on OK button.
Click OK button in the Qgis.bin dialog-box.	Click OK button in the Qgis.bin dialog-box.
Click on Close.	Click on Close button on the DEM (Terrain models) dialog-box.
Cursor on layers panel.	A new layer, Hillshade is now added in the Layers panel. On the canvas you will see a raster map in Hillshade mode.
Cursor on canvas.	This map is generated using light and shadow to create a 3D image.
Cursor on Hillshade layer.	To make the model more pronounced, we will use Hillshade as an overlay.
Cursor on canvas.	Now we will change the symbology of the original DEM layer.
Right-click on the srtm_53_11 layer in the Layers Panel. Select Properties option.	Right-click on the srtm layer in the Layers Panel. From the context menu select Properties option.
Cursor on Layer Properties dialog-box.	Layer Properties dialog-box opens.
Select Style from left panel.	Select Style from the left panel.
Click on Singleband pseudocolor in front of Render type.	Under Band Rendering section, change the Render type to Singleband pseudocolor.
Under Load min/max values, click on min/max.	Under Load min/max values, click on min/max radio button.
Scroll down. Select linear Interpolation. Choose Spectral.	Select Linear from Interpolation drop-down. This is a default selection here. From the Color drop-down select Spectral.
Select Mode as Continuous. Click on Classify button.	Scroll down. Select Mode as Continuous from the drop down. Click on Classify button.
Cursor on the panel.	5 new color values are created. The colors represent values of elevation of raster from lowest to highest.
Click on OK button.	Click on Apply button and OK button at the bottom right corner.
In the Layers panel, Uncheck the check-box for Hillshade layer.	In the Layers panel, disable the Hillshade layer . Uncheck the check-box against Hillshade layer.
Point to the map.	Now on the canvas you will see a map in spectral colors.
Cursor on the panel.	The red shaded terrain is least elevated and blue is most elevated. Enable the Hillshade layer.
Right-click on the Hillshade layer in the Layers Panel. Select Properties option.	Open the Layers Properties dialog-box.
Select Transparency from left panel.	Select Transparency from left panel.
Set the Global transparency to 50%.	Set the Global transparency to 50% by dragging the slider.
Click on OK button.	Click on Apply button and OK button.
Cursor on canvas. Use mouse wheel to zoom in.	Zoom in the map. On the canvas now we see an enhanced topography of the landscape. Disable the Hillshade layer.
Cursor on the canvas.	We can also generate Contour lines for the terrain using tools available in QGIS . Contour tool is available in the Raster menu. We can determine the highest and least elevated point for a particular area.
Slide Number 9 About Contour lines	Contour lines joins points of equal elevation above and below sea level. Contour lines give exact information of the terrain features.
Cursor on the map on QGIS interface.	Back to QGIS canvas. We will select area on this map and draw contour lines.
	Let us clip the area using Clipper tool in the Raster menu.
Click on the menu item Raster Select Extraction from drop down. Select Clipper.	Click on the Raster menu. Click on Extraction from drop down. Click on Clipper.
Cursor on Clipper dialog-box.	Clipper dialog-box opens.
Cursor on Input file field.	Select Input file as the srtm layer. Here, by default this layer is already selected.
Click on Select button next to Output file field.	Click on Select button for Output file.
Point to Select the raster file to save the results to dialog box. In the dialog-box, name the file as Clip-DEM.tif Click on Save button.	save the results dialog box opens. In the dialog-box, name the file as Clip-DEM.tif Click on Save button.
In the Clipper dialog-box, Check the check-box for No data value.	In the Clipper dialog-box, check the check-box for No data value. Let the value be zero.
Under the heading Clipping mode, Click on Extent radio button.	Under the heading Clipping mode, click on Extent radio button. This button is already selected here.
Cursor on QGIS window. Point to cursor. Hold left mouse and draw rectangle over Mumbai.	Switch to the QGIS window. The cursor is now seen as + icon. Hold your left mouse button and draw a rectangle covering the area of interest.
Point to Mumbai region.	For this demonstration I will select Mumbai region.
In the Clipper dialog-box, Check the check-box next to Load into canvas when finished.	In the Clipper dialog-box, Check the check-box next to Load into canvas when finished.
Click on OK button.	Keep other default settings as such. Click on OK button.
Finished dialog-box opens. Click on OK. Click OK button in the Qgis.bin dialog-box.	Once the process finishes, close the pop-up windows by clicking on OK button.
Click on Close button in the Clipper dialog-box.	Click on Close button in the Clipper dialog-box.
Point to Clip-DEM layer.	On the canvas you will see a new layer loaded.
Uncheck check boxes for srtm 51 09, Hillshade, Slope layers.	Disable all the layers in the layers panel, except the newly created Clip-DEM layer.
Cursor on the map.	Now we are ready to generate contour lines for this map using Contour tool.
Click on the Raster menu, select Extraction , from the sub-menu, Click on Contour.	Click on the Raster menu. Scroll down to Extraction , from the sub-menu, click on Contour.
Cursor on Contour dialog-box. From the Input file drop-down select Clip-DEM layer.	Contour dialog-box opens. From the Input file drop-down select Clip-DEM layer.
Click on Select button next to Output file field. Select the raster file to save the results to dialog box opens.	Click on Select button for the Output file. Save the contour output dialog box opens.
Name the file as Contour.shp. Click on Save button	In the dialog-box, name the file as Contour.shp. Click on Save button.
In the Contour dialog box, Select Interval between Contour lines as 50.	In the Contour dialog box, select Interval between Contour lines as 50. This will generate contour lines for 50 meter intervals. You can choose any value according to the requirement.
Click on the check-box next to Attribute name.	Click on the check-box next to Attribute name. Elevation value for each contour line will be recorded as an attribute ELEV.
Check the box next to Load into canvas when finished. Click on OK button.	Check the box next to Load into canvas when finished. Click on OK button.
	Once the process finishes close the pop-up windows by clicking on OK button.
Click on Close button.	Click on Close button to close the Contour dialog-box.
Cursor on Contour layer.	A new layer Contour is added in the layers panel.
Right-click on the Contour layer, click on Open Attribute table.	Open the Attribute table for the Contour layer.
Point to ELEV column on the attribute table.	In the attribute table, each line feature has an attribute named ELEV. The value given in this column is the height in meters for that contour line.
Click on ELEV column header.	Click on the column header a few times to sort the values in descending order.
Point to 1st row.	The first row represents the highest elevation in our data.
Point to last row.	Scroll down the table, the last row represents the lowest elevation.
Click on the first row. Click on Zoom map to the selected rows button in the menu bar.	Scroll up and click on the first row to select it. Click on Zoom map to the selected rows button in the menu bar.
Point to map on QGIS canvas.	Switch to the QGIS window. You will see the selected contour line highlighted in yellow.
Point to the highlighted point.	This is the area of the highest elevation in this dataset.
Slide Number 10 Summary	Let us summarize, In this tutorial we have learnt to Download DEM data from SRTM data website. Show Hillshade of DEM. Clip on area in DEM using the Clipper tool.
Slide Number 11 Summary	Show Contour lines for the DEM. Mark the highest elevated area on the contour map.
Slide Number 12 Assignment 1	Here is the assignment. Visualize the terrain using Slope mode for the raster map. Change the symbology for the Slope layer Hint: Select the Mode as Slope and use it as overlay.
Cursor on the interface.	Your completed assignment should look as shown here.
Slide Number 13 Assignment 2	Create a contour map for the area of your choice. Find the highest elevation for the area.
Slide Number 14 About Spoken Tutorial Project	This video summarizes the Spoken Tutorial project Please download and watch it.
Slide Number 15 Spoken Tutorial Workshops	We conduct workshops using Spoken Tutorials and give certificates. Please contact us.
Slide Number 16 Forum for Specific questions	Please post your timed queries on this forum
Slide number 17 Acknowledgements	The Spoken Tutorial Project is funded by NMEICT, MHRD Government of India.
	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

Karwanjehimanshi95, Snehalathak