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

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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.

Contributors and Content Editors

PoojaMoolya