PoojaMoolya: Created page with " {|border=1 || '''Time''' ||'''Narration''' |- || 00:01 || Welcome to this tutorial on '''Create Contour Lines''' in '''QGIS'''. |- || 00:07 || In this tutorial, we will lear..."

2020-12-21T04:58:06Z

Created page with " {|border=1 || '''Time''' ||'''Narration''' |- || 00:01 || Welcome to this tutorial on '''Create Contour Lines''' in '''QGIS'''. |- || 00:07 || In this tutorial, we will lear..."

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{|border=1
|| '''Time'''
||'''Narration'''
|-
|| 00:01
|| Welcome to this tutorial on '''Create Contour Lines''' in '''QGIS'''.

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|| 00:07
|| In this tutorial, we will learn to,

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|| 00:11
|| Clip the area in '''DEM''' using the '''Clipper''' tool.

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|| 00:16
|| Show '''contour''' lines for the '''DEM'''.

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|| 00:20
|| And mark the highest elevated area on the '''contour '''map.

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|| 00:26
|| Here I am using

'''Ubuntu Linux '''OS version 16.04

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|| 00:32
|| QGIS version 2.18

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|| 00:36
|| And a working Internet connection.

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|| 00:40
|| To follow this tutorial you should be familiar with '''QGIS''' interface.

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|| 00:46
|| For the prerequisite tutorials in this series please visit this website.

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|| 00:53
||'''DEM''' data required to practise this tutorial is provided in the '''Code files''' link.

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|| 01:00
|| Please download and extract the contents of the folder.

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|| 01:05
||I have saved this folder on the '''Desktop'''.

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|| 01:09
|| Double-click on the folder to open it.

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|| 01:13
|| Right-click on '''srtm.tif''' file and select '''Open with QGIS Desktop'''.

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|| 01:22
|| The map opens on the screen.

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|| 01:25
|| You can also open the '''tif '''file using '''Add Raster Layer '''option in '''Layer''' menu.

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|| 01:33
|| On the canvas you will see '''DEM''' of the terrain.

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|| 01:38
||'''Contour lines''' for this '''DEM''' can be generated using '''Contour tool''' in '''Raster menu'''.

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|| 01:46
||About '''Contour lines'''.

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|| 01:49
|| It is a line on a map joining points of equal height above or below sea level.

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|| 01:57
|| Contour lines help us to determine the highest and least elevated areas on the map.

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|| 02:04
||We can draw contour lines for the selected area on this map.

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|| 02:10
||We will use the '''Clipper''' tool in the '''Raster''' menu to clip the area.

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|| 02:16
||Click on the '''Raster '''menu.

Click on '''Extraction''' from drop-down.

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|| 02:23
|| Click on '''Clipper'''.

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|| 02:26
||'''Clipper''' dialog-box opens.

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|| 02:29
||Select '''Input file''' as the '''DEM''' layer.

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|| 02:33
|| Here, by default this layer is already selected.

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|| 02:38
||Click on '''Select''' button for '''Output file'''.

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|| 02:42
||'''Select the raster file to save the results to''' dialog-box opens.

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|| 02:48
|| In the dialog-box, name the file as '''Clip-DEM.tif'''.

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|| 02:56
|| Click on '''Save '''button at the bottom right corner.

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|| 03:01
||In the '''Clipper''' dialog-box, check the check-box for '''No data value'''.

Let the value be zero.

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|| 03:10
||Under the heading '''Clipping mode''', click on '''Extent''' radio button.

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|| 03:16
||Switch to the '''QGIS''' window.

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|| 03:19
|| The cursor is now seen as '''plus'''(+) sign.

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|| 03:23
|| Hold your left mouse button and draw a rectangle covering the area of interest.

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|| 03:30
|| For this demonstration I will select Mumbai region.

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||03:35
||In the '''Clipper''' dialog-box, check the check-box next to '''Load into canvas when finished'''.

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|| 03:42
||Keep other default settings as such.

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|| 03:46
|| Click on '''OK''' button at the bottom right corner.

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|| 03:51
||Once the process completes, close the pop-up windows by clicking on '''OK''' buttons.

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|| 03:58
|| Click on '''Close''' button at the bottom right corner in the '''Clipper''' dialog-box.

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|| 04:05
||On the canvas you will see a new layer loaded.

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||04:10
||Disable all the layers in the '''Layers Panel''', except '''Clip-DEM''' layer.

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|| 04:16
|| Now we are ready to generate contour lines for this map using '''Contour''' tool.

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|| 04:23
||Click on the '''Raster '''menu.

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|| 04:26
|| Scroll down to '''Extraction'''.

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|| 04:29
|| From the sub-menu, click on '''Contour'''.

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||04:34
||'''Contour''' dialog-box opens.

From the '''Input file''' drop-down, select '''Clip-DEM''' layer.

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|| 04:43
||Click on '''Select '''button for the '''Output file'''.

Dialog-box opens.

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|| 04:51
||In the dialog-box, name the file as '''Contour.shp'''.

Click on '''Save''' button.

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|| 05:00
||In the '''Contour''' dialog box, select '''Interval between contour lines''' as 50.

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|| 05:07
|| This will generate contour lines for 50 meter intervals.

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|| 05:12
||Click on the check-box next to '''Attribute name'''.

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|| 05:17
|| Elevation value for each contour line will be recorded as an attribute '''E L E V'''.

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|| 05:24
||Check the box next to '''Load into canvas''' '''when finished'''.

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|| 05:29
|| Click on '''OK''' button at the bottom right corner in the contour dialog box.

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|| 05:36
||Once the process completes, close the pop-up windows by clicking on '''OK''' buttons.

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|| 05:43
|| Click on '''Close''' button to close the '''Contour''' dialog-box.

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|| 05:48
||A new layer '''Contour''' is added in the '''Layers panel'''.

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|| 05:53
||Let us change the colour of the contour lines.

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|| 05:57
|| Right click on '''Contour''' layer.

Select '''Styles'''.

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|| 06:03
|| Rotate the triangle to change the colour.

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|| 06:07
|| Choose the colour of your choice.

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|| 06:11
|| Hide the other layers by un-checking the check-boxes in the '''Layers panel'''.

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|| 06:17
||Open the '''Attribute table '''for the '''Contour''' layer.

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|| 06:21
||In the attribute table, each line feature has an attribute named '''E L E V'''.

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|| 06:28
|| The value given in this column is the height in meters for that contour line.

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|| 06:35
||Click on the column header a few times to sort the values in descending order.

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|| 06:42
|| The first row represents the highest elevation in our data.

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|| 06:47
||Scroll down the table, the last row represents the lowest elevation.

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|| 06:54
||Scroll up and click on the first row to select it

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|| 06:59
|| Click on '''Zoom map to the selected rows''' button on the tool bar.

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|| 07:06
||Switch to the '''QGIS''' window.

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|| 07:09
|| You will see the selected contour line highlighted in yellow.

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|| 07:14
||This is the area of the highest elevation in this '''data-set'''.

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|| 07:20
||Save this project.

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|| 07:23
|| Click on “'''Save As'''” tool on the tool bar.

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|| 07:27
|| Give an appropriate name.

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|| 07:30
|| Save it at a convenient location.

Click on '''Save''' button.

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|| 07:37
|| Let us summarize,

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|| 07:39
|| In this tutorial we have learnt to

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|| 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.

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|| 07:56
||Here is the assignment.

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|| 07:59
|| Create '''contour '''lines for the area of your choice on the '''DEM'''.

Find the highest elevation for the area.

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|| 08:09
||This video summarizes the Spoken Tutorial project.

Please download and watch it.

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|| 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.
|-
|}

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

PoojaMoolya: Created page with " {|border=1 || '''Time''' ||'''Narration''' |- || 00:01 || Welcome to this tutorial on '''Create Contour Lines''' in '''QGIS'''. |- || 00:07 || In this tutorial, we will lear..."