PoojaMoolya at 09:20, 22 December 2020

2020-12-22T09:20:21Z

PoojaMoolya: Created page with " {|border=1 || '''Time''' || '''Narration''' |- || 00:01 || Welcome to this tutorial on '''Interpolation Methods''' in QGIS. |- || 00:07 || In this tutorial, we will learn ab..."

2020-09-15T05:33:10Z

Created page with " {|border=1 || '''Time''' || '''Narration''' |- || 00:01 || Welcome to this tutorial on '''Interpolation Methods''' in QGIS. |- || 00:07 || In this tutorial, we will learn ab..."

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

|-
|| 00:07
|| In this tutorial, we will learn about Interpolation methods.

|-
|| 00:12
|| '''Inverse Distance Weighting (IDW)''' and

'''Triangulated Irregular Network (TIN)'''

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|| 00:18
|| Here I am using

'''Ubuntu Linux''' OS version 16.04

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|| 00:24
||'''QGIS''' version 2.18

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|| 00:28
|| To follow this tutorial you should be familiar with '''QGIS''' interface.

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|| 00:34
||For the prerequisite tutorials in this series, please visit this website.

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|| 00:40
|| Data files required for this tutorial are provided in the '''Code files''' link.

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|| 00:46
||Please download and extract the contents of the folder.

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|| 00:51
|| I have saved this folder on the '''Desktop'''.

Double-click on the folder to open it.

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|| 00:59
|| Locate '''Air Stations.shp''' in the extracted folder.

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|| 01:04
||This file shows meteorological stations located in Maharashtra.

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|| 01:10
|| '''Interpolation''' is a method to create continuous surface from discrete points.

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|| 01:17
||Two methods of '''interpolation''' are available in '''QGIS'''.

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|| 01:22
|| '''Inverse Distance Weighting (IDW)''' and '''Triangulated Irregular Network (TIN)'''

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|| 01:28
|| '''Interpolation Plugin''' is used to create '''interpolated raster''' from '''Point layer'''.

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||01:35
|| Open the '''QGIS''' interface.

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|| 01:38
|| Here I have opened the '''QGIS''' interface.

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|| 01:43
|| Enable the interpolation plugin using '''Plugins''' menu as shown here.

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|| 01:49
|| Check the check-box for '''Interpolation plugin'''.

Close the dialog-box.

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|| 01:56
|| Open the '''Raster''' menu.

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|| 01:59
|| '''Interpolation''' option is now added in the '''Raster''' menu.

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|| 02:04
|| Click on '''Add Vector Layer''' tool. '''Add vector layer''' dialog-box opens.

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|| 02:11
|| Click on '''Browse''' button and navigate to '''Code files''' folder.

Here we will select two files.

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|| 02:20
|| Select '''AirStations.shp''' file.

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|| 02:24
|| Hold the '''Ctrl''' key on the keyboard and click on '''MH_Districts.shp'''.

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|| 02:32
|| Click on the '''Open''' button.

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|| 02:35
|| Click on '''Open''' button on the '''Add vector layer''' dialog-box.

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|| 02:40
|| On the canvas we see map of Maharashtra state.

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|| 02:45
|| Locations of '''Air stations''' in each district are shown as point features.

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|| 02:52
|| Let us label these point features.

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|| 02:56
|| Right click on the '''Air Stations layer'''.

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|| 03:00
|| Click on '''Properties '''option to open '''Layer Properties''' dialog box.

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|| 03:06
|| Select the '''Labels''' option located on the left panel.

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|| 03:11
|| Click on the drop-down located at the top.

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|| 03:15
|| Select '''Show labels for this layer''' from the drop-down.

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|| 03:20
|| In the '''Label with''' drop-down select '''Air_Pollut'''.

Scroll down.

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|| 03:28
|| Here you will find various options to modify the label style.

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|| 03:33
||Choose the required style and click on '''OK''' button.

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|| 03:38
|| On the canvas, points with the labels will be displayed.

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|| 03:43
|| Open the '''attribute''' table for '''Air Stations.shp layer.'''

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|| 03:49
|| In the '''attribute''' table there are five columns.

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|| 03:53
||In the 4th column, '''Nitrogen Oxides''' levels for every station is given.

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|| 04:00
|| We will '''interpolate Air Stations layer''' by the '''Nox attribute'''.

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|| 04:06
||Here we will use '''IDW method''' for '''interpolation'''.

Close the '''attribute''' table.

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|| 04:14
|| '''Inverse Distance Weighting''' method gives weights to sample points.

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|| 04:20
||It is used for '''interpolating''' data such as temperature, rainfall, population etc.

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|| 04:29
|| Back to the '''QGIS''' interface.

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|| 04:32
|| Click on the '''Raster''' menu.

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|| 04:35
|| Click on the '''interpolation '''plugin.

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|| 04:38
||'''Interpolation plugin''' dialog-box opens.

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|| 04:42
|| In the''' Input''' section,

Select '''Air Stations''' as option as the '''Vector layers'''.

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|| 04:49
||Here, by default, '''Air Stations layer''' is already selected.

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|| 04:55
|| Select '''Interpolation attribute''' as '''NOx'''.

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|| 05:00
|| Click on the '''Add '''Button.

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|| 05:03
||This will add '''Air Stations.shp layer''' with '''NOx''' attribute.

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|| 05:09
||Select '''Points '''in the ''' Type'''drop-down.

Here '''Points''' is selected by default.

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|| 05:17
|| Go to the '''Output''' section.

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|| 05:20
||Select '''Interpolation method''' as '''Inverse Distance Weighting'''.

Leave all the settings as '''default'''.

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|| 05:29
|| Click on the three dots button next to '''Output file'''.

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|| 05:33
||Save the output as an '''IDW_Stations''' in the desired folder.

I will save it on '''Desktop'''.

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|| 05:43
|| Check, '''Add result to project''' if it is unchecked.

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|| 05:48
|| Click on '''OK''' button.

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|| 05:50
|| The map with '''black''' and '''white''' areas will be displayed on the screen.

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|| 05:56
||White areas represent high levels of '''Nitrogen Oxides'''.

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|| 06:01
|| Black areas represent low levels of '''Nitrogen Oxides'''.

|-
|| 06:06
|| For more clarity, we will change the symbology of the '''layer'''.

|-
|| 06:11
|| Open '''Layer properties''' for the '''IDW layer'''.

|-
|| 06:16
|| From the left panel, click on the '''Style '''option.

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|| 06:20
||Select '''Render type''' as '''Single band Pseudocolor'''.

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|| 06:25
|| Select '''Discrete''' from '''Interpolation''' drop-down.

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|| 06:29
||Choose '''Spectral''' from color drop-down. Check the '''Invert''' check-box.

|-
|| 06:36
|| Click on the '''Classify''' button.

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|| 06:39
||Leave all other settings as default.

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|| 06:43
||Click on '''Apply''' and '''OK''' button.

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|| 06:47
|| Map with areas in '''Spectral''' colors is displayed on the canvas.

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|| 06:53
||The red colored areas have high concentration of '''Nitrogen Oxides'''.

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|| 06:59
||Blue areas have least concentration of '''Nitrogen Oxides'''.

|-
|| 07:04
|| Save the '''project''' using '''Save''' tool from the tool bar.

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|| 07:09
||Give an appropriate name. Choose a convenient location.

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|| 07:15
||Click on '''Save''' button.

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|| 07:18
|| Let us now learn about the '''Triangulated Irregular Network interpolation''' method.

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|| 07:25
||'''TIN '''is used to create a surface formed by triangles.

|-
|| 07:31
||This is based on '''nearest neighbor point '''information.

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|| 07:36
||'''TIN '''method is commonly used for elevation data.

|-
|| 07:41
|| Open a new '''QGIS''' window.

Click on '''New''' tool on the tool bar.

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|| 07:48
|| Use the '''Add Vector Layer''' tool to load '''Points.shp layer.'''

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|| 07:55
||Open '''Attribute table''' of '''Points layer'''.

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|| 07:59
|| Notice the '''Elevation''' data for each point feature.

|-
|| 08:04
|| Close the '''Attribute''' table.

|-
|| 08:07
|| Again open '''Interpolation window''' from '''Raster''' menu.

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|| 08:12
|| In the''' Input''' section, select '''Points layer''' in the '''Vector layers''' drop-down.

Select '''elevation '''as''' Interpolation attribute'''.

|-
|| 08:23
|| Click on '''Add''' button.

This will add '''Points layer''' with '''elevation attribute''' for '''interpolating'''.

|-
|| 08:31
||'''Points''' in '''Type''' drop-down is chosen automatically.

Leave it as such.

|-
|| 08:37
|| In the '''Output''' section, select '''Triangular interpolation''' as '''Interpolation method'''.

|-
|| 08:44
||Save the '''output''' file as '''TIN-Stations''' and click '''OK button.'''

|-
|| 08:52
|| Map showing '''triangulated interpolation''' appears on the canvas.

|-
|| 08:57
|| Change the '''symbology''' for this '''layer'''.

|-
|| 09:01
||Follow the same steps as we did for '''IDW layer'''.

|-
|| 09:15
|| The map is now displayed in '''Spectral''' colors.

Areas in red represent high elevation.

|-
|| 09:24
||Areas in blue represent low elevation.

|-
|| 09:28
|| Save the maps using the '''Save''' tool on the toolbar.

|-
|| 09:33
|| Let us summarize,

In this tutorial we have learnt about two methods of '''Interpolation'''.

|-
|| 09:40
|| '''Inverse Distance Weighting (IDW)''' and '''Triangulated Irregular Network''' '''(TIN)'''
|-
|| 09:46
|| For the assignment,

Create '''IDW interpolated''' map for '''Air Stations layer''' with '''SO<sub>2 </sub>attribute'''.

|-
|| 09:55
|| Your map should look as shown here.

|-
|| 09:59
|| This video summarizes the Spoken Tutorial project.

Please download and watch it.

|-
||10:06
|| The spoken tutorial project team conducts workshops and gives certificates.

For more details please write to us.

|-
|| 10:16
|| Please post your timed queries in this forum.

|-
|| 10:20
|| The Spoken Tutorial project is funded by '''MHRD''' '''Government of India'''.

This tutorial is contributed by Ambadas Maske from College of Engineering Pune.

Snehalatha Kaliappan and Himanshi Karwanje from IIT Bombay.Thank you for joining.
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|}

QGIS/C4/Interpolation/English-timed - Revision history

PoojaMoolya at 09:20, 22 December 2020

PoojaMoolya: Created page with " {|border=1 || '''Time''' || '''Narration''' |- || 00:01 || Welcome to this tutorial on '''Interpolation Methods''' in QGIS. |- || 00:07 || In this tutorial, we will learn ab..."