QGIS/C4/Create-Contour-Lines/English-timed

Time	Narration
00:01	Welcome to this tutorial on Create Contour Lines in QGIS.
00:07	In this tutorial, we will learn to,
00:11	Clip the area in DEM using the Clipper tool.
00:16	Show contour lines for the DEM.
00:20	And mark the highest elevated area on the contour map.
00:26	Here I am using Ubuntu Linux OS version 16.04
00:32	QGIS version 2.18
00:36	And a working Internet connection.
00:40	To follow this tutorial you should be familiar with QGIS interface.
00:46	For the prerequisite tutorials in this series please visit this website.
00:53	DEM data required to practise this tutorial is provided in the Code files link.
01:00	Please download and extract the contents of the folder.
01:05	I have saved this folder on the Desktop.
01:09	Double-click on the folder to open it.
01:13	Right-click on srtm.tif file and select Open with QGIS Desktop.
01:22	The map opens on the screen.
01:25	You can also open the tif file using Add Raster Layer option in Layer menu.
01:33	On the canvas you will see DEM of the terrain.
01:38	Contour lines for this DEM can be generated using Contour tool in Raster menu.
01:46	About Contour lines.
01:49	It is a line on a map joining points of equal height above or below sea level.
01:57	Contour lines help us to determine the highest and least elevated areas on the map.
02:04	We can draw contour lines for the selected area on this map.
02:10	We will use the Clipper tool in the Raster menu to clip the area.
02:16	Click on the Raster menu. Click on Extraction from drop-down.
02:23	Click on Clipper.
02:26	Clipper dialog-box opens.
02:29	Select Input file as the DEM layer.
02:33	Here, by default this layer is already selected.
02:38	Click on Select button for Output file.
02:42	Select the raster file to save the results to dialog-box opens.
02:48	In the dialog-box, name the file as Clip-DEM.tif.
02:56	Click on Save button at the bottom right corner.
03:01	In the Clipper dialog-box, check the check-box for No data value. Let the value be zero.
03:10	Under the heading Clipping mode, click on Extent radio button.
03:16	Switch to the QGIS window.
03:19	The cursor is now seen as plus(+) sign.
03:23	Hold your left mouse button and draw a rectangle covering the area of interest.
03:30	For this demonstration I will select Mumbai region.
03:35	In the Clipper dialog-box, check the check-box next to Load into canvas when finished.
03:42	Keep other default settings as such.
03:46	Click on OK button at the bottom right corner.
03:51	Once the process completes, close the pop-up windows by clicking on OK buttons.
03:58	Click on Close button at the bottom right corner in the Clipper dialog-box.
04:05	On the canvas you will see a new layer loaded.
04:10	Disable all the layers in the Layers Panel, except Clip-DEM layer.
04:16	Now we are ready to generate contour lines for this map using Contour tool.
04:23	Click on the Raster menu.
04:26	Scroll down to Extraction.
04:29	From the sub-menu, click on Contour.
04:34	Contour dialog-box opens. From the Input file drop-down, select Clip-DEM layer.
04:43	Click on Select button for the Output file. Dialog-box opens.
04:51	In the dialog-box, name the file as Contour.shp. Click on Save button.
05:00	In the Contour dialog box, select Interval between contour lines as 50.
05:07	This will generate contour lines for 50 meter intervals.
05:12	Click on the check-box next to Attribute name.
05:17	Elevation value for each contour line will be recorded as an attribute E L E V.
05:24	Check the box next to Load into canvas when finished.
05:29	Click on OK button at the bottom right corner in the contour dialog box.
05:36	Once the process completes, close the pop-up windows by clicking on OK buttons.
05:43	Click on Close button to close the Contour dialog-box.
05:48	A new layer Contour is added in the Layers panel.
05:53	Let us change the colour of the contour lines.
05:57	Right click on Contour layer. Select Styles.
06:03	Rotate the triangle to change the colour.
06:07	Choose the colour of your choice.
06:11	Hide the other layers by un-checking the check-boxes in the Layers panel.
06:17	Open the Attribute table for the Contour layer.
06:21	In the attribute table, each line feature has an attribute named E L E V.
06:28	The value given in this column is the height in meters for that contour line.
06:35	Click on the column header a few times to sort the values in descending order.
06:42	The first row represents the highest elevation in our data.
06:47	Scroll down the table, the last row represents the lowest elevation.
06:54	Scroll up and click on the first row to select it
06:59	Click on Zoom map to the selected rows button on the tool bar.
07:06	Switch to the QGIS window.
07:09	You will see the selected contour line highlighted in yellow.
07:14	This is the area of the highest elevation in this data-set.
07:20	Save this project.
07:23	Click on “Save As” tool on the tool bar.
07:27	Give an appropriate name.
07:30	Save it at a convenient location. Click on Save button.
07:37	Let us summarize,
07:39	In this tutorial we have learnt to
07:42	Clip the area in DEM using the Clipper tool.
07:47	Show contour lines for the DEM.
07:51	Mark the highest elevated area on the contour map.
07:56	Here is the assignment.
07:59	Create contour lines for the area of your choice on the DEM. Find the highest elevation for the area.
08:09	This video summarizes the Spoken Tutorial project. Please download and watch it.
08:16	The spoken tutorial project team conducts workshops and gives certificates. For more details please write to us.
08:26	Please post your timed queries in this forum.
08:30	The Spoken Tutorial Project is funded by NMEICT, MHRD Government of India.
08:38	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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