QGIS/C4/DEM-Analysis/English-timed

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.
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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.

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