IDW interpolation using QGIS - Revision history

Pulsiferpl: Minor edits of typographical and style issues

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 == Introduction and Purpose ==
-Using spatial data, it is possible to analyze, interpret, and represent phenomena almost everywhere on Earth. But what can be done when data exists near our area of interest, but not directly at the location? In these situations, we can use Inverse Distance Weighting (IDW) interpolation, a process which calculates values for locations based on nearby known values. It operates on the first law of geography, which states that near things are more alike than far things and assigns greater influence to known values which are nearby than those that are distant. In this tutorial, we will be conducting IDW interpolation in QGIS, an open-source GIS system. Open-source ([https://en.wikipedia.org/wiki/Open_source]) is a term that refers to having accessible, free and redistributable programs available to the public. This allows for individuals to work on the code together to create a model that encourages open collaboration and develops code together. To look at GIS programs available for free download, you can visit the [https://www.osgeo.org/choose-a-project/] page to look at all the projects currently being worked on by the community.
+Using spatial data, it is possible to analyze, interpret, and represent phenomena almost everywhere on Earth. But what can be done when data exists near our area of interest, but not directly at the location? In these situations, we can use Inverse Distance Weighting (IDW) interpolation, a process that calculates values for locations based on nearby known values. It operates on the first law of geography, which states that near things are more alike than far things and assigns greater influence to known values that are nearby than those that are distant. In this tutorial, we will be conducting IDW interpolation in QGIS, an open-source GIS system. Open-source ([https://en.wikipedia.org/wiki/Open_source]) is a term that refers to having accessible, free, and redistributable programs available to the public. This allows for individuals to work on the code together to create a model that encourages open collaboration and develops code together. To look at GIS programs available for free download, you can visit the [https://www.osgeo.org/choose-a-project/] page to look at all the projects currently being worked on by the community.
 The purpose of this tutorial is to expand your abilities in QGIS by teaching you how to run an important analysis tool- IDW interpolation [[http://en.wikipedia.org/wiki/Interpolation]], with the end goal of creating an interpolated raster surface. The difficulty level for this tutorial is an entry-level QGIS user. This tutorial will contain screen-shots for each step to show the path to create all the layers that are in the finished product.
@@ Line 17: / Line 17: @@
 == Data ==
-The data used in this tutorial is monthly climate summaries from Statistics Canada, which publishes extensive and easily accessible data for all provinces and territories in Canada. For more information about the data, visit the "About the Data" page here [[https://climate.weather.gc.ca/]]. This in-depth look at provincial weather will be an easily malleable data set to use for the tutorial. In this example, we will be looking at Alberta's average mean temperature. This will give us a well-distributed data set that we will be able to use to create an IDW model and help us calculate the approximate  temperature values of areas that do not have weather stations.
+The data used in this tutorial is monthly climate summaries from Statistics Canada, which publishes extensive and easily accessible data for all provinces and territories in Canada. For more information about the data, visit the "About the Data" page here [[https://climate.weather.gc.ca/]]. This in-depth look at provincial weather will be an easily malleable data set to use for the tutorial. In this example, we will be looking at Alberta's average mean temperature. This will give us a well-distributed data set that we will be able to use to create an IDW model and help us calculate the approximate temperature values of areas that do not have weather stations.
 ===Downloading the data===
 # First, set up a folder in your file directory for your project. This will be where you save all your data and your QGIS project
 # Next, go to [[https://climate.weather.gc.ca/prods_servs/cdn_climate_summary_e.html]] and set the date to December of 2019
-# Select your area of interest (for this assessment Alberta was used as it has the most climate stations in the country)
+# Select your area of interest (for this assessment, Alberta was used as it has the most climate stations in the country)
 # Select CSV as the data format and click "Download data" to start your download
 # You can also download the Legend(txt) file as it will allow you to see what all the data is meant to represent
@@ Line 36: / Line 36: @@
 <br clear=all>
 ===Editing the data===
-With this data having so many variables we need to edit it to make it easier to work with:
+With this data having so many variables, we need to edit it to make it easier to work with:
 # Open your CSV file using a spreadsheet software like Excel
-# Right click on the "Clim_ID" column to select the entire row
+# Right-click on the "Clim_ID" column to select the entire row
 # Use the sort/filter drop-down menu and filter the "Clim_ID" column from largest to smallest
 # Select the rows with values that contain letters and delete them from your file. These rows are not needed and can create some issues when loading the data into QGIS
@@ Line 72: / Line 72: @@
 <br clear=all>
-* In the pop up window, click the 3 dots at the top right corner of the screen (highlighted in blue in the image below) and navigate to your project folder. Select the climate summary CSV file. In the Geometry definition option set your x field to "Long" and your y field to "Lat" (highlighted in yellow) to set your coordinates
+* In the pop up window, click the 3 dots at the top right corner of the screen (highlighted in blue in the image below) and navigate to your project folder. Select the climate summary CSV file. In the Geometry definition option, set your x field to "Long" and your y field to "Lat" (highlighted in yellow) to set your coordinates
 [[File:CSVI 2.png|600px|thumb|center]]
@@ Line 82: / Line 82: @@
 <br clear=all>
-* In the pop up window, click the 3 dots at the top right corner of the screen (highlighted in blue in the image below) and navigate to your project folder. Select boundary file with a .shp ending
+* In the pop-up window, click the 3 dots at the top right corner of the screen (highlighted in blue in the image below) and navigate to your project folder. Select the boundary file with a .shp ending
 [[File:VI 2.png|600px|thumb|center]]
@@ Line 88: / Line 88: @@
 * Right-click on the boundary layer and select "Open attribute table"
-* In the pop up window, click the pencil (circled in yellow) at the top right of the window to begin editing. Select all layers except Alberta and click the " Delete Selected Feature" tool (circled in red) on the menu
+* In the pop-up window, click the pencil (circled in yellow) at the top right of the window to begin editing. Select all layers except Alberta and click the "Delete Selected Feature" tool (circled in red) on the menu
 [[File:AT 1.png|600px|thumb|center]]
@@ Line 94: / Line 94: @@
 * Right-click on the boundary and toggle editing to stop editing the layer. Select the "Save your Edits" option from the ensuing pop-up
-* The following step is to save both of your layers as individual files. If this is not done, they will have to be re-created each time you open you open your project. To do this right-click on the layer, click "Export", the select "Save Feature As"
+* The following step is to save both of your layers as individual files. If this is not done, they will have to be re-created each time you open your project. To do this, right-click on the layer, click "Export", then select "Save Feature As"
 [[File:SVS 1.png|600px|thumb|center]]
 <br clear=all>
-* In the pop up window, click the 3 dots (highlighted in blue) and navigate to your project folder. Give your feature an appropriate name and then click "Okay"
+* In the pop-up window, click the 3 dots (highlighted in blue) and navigate to your project folder. Give your feature an appropriate name, and then click "Okay"
 * Repeat this step for both the boundary and weather station layers
@@ Line 121: / Line 121: @@
 <br clear=all>
-* In the new window, select the weather stations layer from the "Vector layer"  drop-down. Next, select "Tm" as from the "Interpolation attribute" drop-down to assign the mean temperature as the value we are interpolating
+* In the new window, select the weather stations layer from the "Vector layer"  drop-down. Next, select "Tm" from the "Interpolation attribute" drop-down to assign the mean temperature as the value we are interpolating
 * Click the plus button (highlighted in yellow) to add the stations layer to the "Vector layer" list. Select the "points" tab under the "Type" drop-down
@@ Line 132: / Line 132: @@
 <br clear=all>
-* Once the processing is complete the result should resemble the image below
+* Once the processing is complete, the result should resemble the image below
 [[File:IDW 3.png|600px|thumb|center]]
@@ Line 146: / Line 146: @@
 <br clear=all>
-* In the window select your interpolated layer as the "Input Layer". Next, select the boundary layer as the "Mask Layer"
+* In the window, select your interpolated layer as the "Input Layer". Next, select the boundary layer as the "Mask Layer"
 [[File:Clip 2.png|600px|thumb|center]]
 <br clear=all>
-* Right-click on the new layer and select the "Properties" button at the bottom of the pop up menu
+* Right-click on the new layer and select the "Properties" button at the bottom of the pop-up menu
-* In the new window, change the "Render type" to "Singleband pseudocolor" using the drop-down menu (highlighted in yellow). Next select the red to blue colour ramp using the "Color ramp" drop-down and selecting "All Color Ramps". Invert the colour ramp so that red represents higher temperatures and blue colder using the "Invert Color Ramp" function in the "Color ramp" drop-down (highlighted in blue)
+* In the new window, change the "Render type" to "Singleband pseudocolor" using the drop-down menu (highlighted in yellow). Next, select the red to blue colour ramp using the "Color ramp" drop-down and selecting "All Color Ramps". Invert the colour ramp so that red represents higher temperatures and blue colder using the "Invert Color Ramp" function in the "Color ramp" drop-down (highlighted in blue)
 [[File:Col 1.png|600px|thumb|center]]
 <br clear=all>
-* Next export the layer by right-clicking and selecting "Export" and "Save Feature As".
+* Next, export the layer by right-clicking and selecting "Export" and "Save Feature As".
 * Set the "Format" to GeoTIFF and click the three dots to navigate to your project folder. Name your file, then click "OK" to save
@@ Line 169: / Line 169: @@
-* Once this is completed the the tutorial is over and you successfully ran an interpolation on open source software! Thank you for following along, and we hope that this has been helpful - Pierce and Alex
+* Once this is completed, the tutorial is over and you successfully ran an interpolation on open-source software! Thank you for following along, and we hope that this has been helpful - Pierce and Alex

@@ Line 5: / Line 5: @@
 [[File:QGIS logo.png|thumb]]
 <br clear=all>
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 =Tutorial=

@@ Line 2: / Line 2: @@
 Using spatial data, it is possible to analyze, interpret, and represent phenomena almost everywhere on Earth. But what can be done when data exists near our area of interest, but not directly at the location? In these situations, we can use Inverse Distance Weighting (IDW) interpolation, a process which calculates values for locations based on nearby known values. It operates on the first law of geography, which states that near things are more alike than far things and assigns greater influence to known values which are nearby than those that are distant. In this tutorial, we will be conducting IDW interpolation in QGIS, an open-source GIS system. Open-source ([https://en.wikipedia.org/wiki/Open_source]) is a term that refers to having accessible, free and redistributable programs available to the public. This allows for individuals to work on the code together to create a model that encourages open collaboration and develops code together. To look at GIS programs available for free download, you can visit the [https://www.osgeo.org/choose-a-project/] page to look at all the projects currently being worked on by the community.
-The purpose of this tutorial is to expand your abilities in QGIS by teaching you how to run an important analysis tool- IDW interpolation [[http://en.wikipedia.org/wiki/Interpolation]], with the end goal of creating an interpolated raster surface. The difficulty level for this tutorial is an entry-level QGIS user. This tutorial will contain screen-shots for each step to show the path to create all the layers that are in the finished product
+The purpose of this tutorial is to expand your abilities in QGIS by teaching you how to run an important analysis tool- IDW interpolation [[http://en.wikipedia.org/wiki/Interpolation]], with the end goal of creating an interpolated raster surface. The difficulty level for this tutorial is an entry-level QGIS user. This tutorial will contain screen-shots for each step to show the path to create all the layers that are in the finished product.
 [[File:QGIS logo.png|thumb]]
+<br clear=all>
 ------------------------------------------------------------------------------------------------------------------------------------
 =Tutorial=

← Older revision		Revision as of 01:31, 30 September 2023
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	* Once this is completed the the tutorial is over and you successfully ran an interpolation on open source software!		* Once this is completed the the tutorial is over and you successfully ran an interpolation on open source software! Thank you for following along, and we hope that this has been helpful - Pierce and Alex

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-==Interpolating data to create a Raster Surface layer==
-[[File:Screen Shot 2021-12-23 at 12.16.29 AM.png|thumb]]
-#Begin by clicking the processing tab at the top of the application window and selecting the
-"toolbox" tab. This should bring up a menu on the left side of the application with a search bar at the top of its menu.
-#in the search bar type in "IDW Interpolation". there will be several options that come up but for our tutorial, we will be using the proprietary tool that QGIS officially backs and created for its software. Once you have located it double click the tool to open the IDW window
-#In the new window, where it says "Vector layer" select the name of the weather station layer we created earlier. Once this is done it will ask for the interpolation attribute that you will be interpolating, select the "Tm" attribute as this is what we will be working with
-#right bellow interpolation attribute drop down there is a plus button, click this and the layer will be added the table below. In this table select the "points" tab under the type dropdown.
-# below this we have the Distance coefficient P set at a default of 2, I would recommend increasing this to 5 to account for the northern and western portion of Alberta since these areas have very little station data available compared to southern Alberta. this will add more weight to pixel values and their distance to other stations.
-#below this there is the extent tab with a dropdown on the right side of the terminal, click this and go to calculate from layer, this will bring up the other layers currently on your map. Select your boundary file as the extent
-# if everything is done correctly it should look like the picture shown below. if it does click the "Run" button at the bottom of the window.
+===Interpolating data to create a Raster Surface layer===
+* Click the processing tab or the gear icon in the menu
+[[File:MENU 1.png|400px|thumb]]
-----------------------------------------------------------------------------------------------------------------------------------
+* This will bring up a menu on the left side of the application with a search bar at the top of its menu. Click on the "Interpolation" row to open the sub-menu. Once you have located it, double-click "IDW Interpolation" (highlighted in yellow) to open the tool window
-==Clipping Interpolation Surface to create a final raster layer==
+[[File:TB 1.png|300px|thumb]]
+* In the new window, select the weather stations layer from the "Vector layer"  drop-down. Next, select "Tm" as from the "Interpolation attribute" drop-down to assign the mean temperature as the value we are interpolating
+* Click the plus button (highlighted in yellow) to add the stations layer to the "Vector layer" list. Select the "points" tab under the "Type" drop-down
+[[File:IDW 1.png|300px|thumb]]
+* Click the drop-down by the "Extent" option to limit the extent of the interpolation. Click "Calculate from Layer" and select your boundary file as the extent
+[[File:IDW 2.png|300px|thumb]]
+* Once the processing is complete the result should resemble the image below
+[[File:IDW 3.png|300px|thumb]]
+===Clipping Interpolation Surface to create a final raster layer===
 * This portion of the tutorial will focus on creating a masked layer for the raster layer we just created to fit within our boundary file.

@@ Line 88: / Line 88: @@
 * Right-click on the boundary and toggle editing to stop editing the layer. Select the "Save your Edits" option from the ensuing pop-up
-* once this is complete correctly you should only have the Alberta boundary file on your project layer (and the weather stations)
-[[File:Screen Shot 2021-12-22 at 10.32.11 PM.png|thumb]]
-# The next step will be to create a permeate layer for your weather station points. to do this right-click on the layer and click export "save feature as"
-#Give this a name and click the 3 dots next to your name for the layer. create a space where you will be saving all your file layers ( I would recommend creating a new folder to keep everything in to keep all your paths the same for the project) once all of this is done it should look something like this
-[[File:Screen Shot 2021-12-22 at 11.23.32 PM.png|thumb]]
+* The following step is to save both of your layers as individual files. If this is not done, they will have to be re-created each time you open you open your project. To do this right-click on the layer, click "Export", the select "Save Feature As"
+[[File:SVS 1.png|300px|thumb]]
+* In the pop up window, click the 3 dots (highlighted in blue) and navigate to your project folder. Give your feature an appropriate name and then click "Okay"
+* Repeat this step for both the boundary and weather station layers
+[[File:SVS 2.png|300px|thumb]]
+---------------------------------------------------------------------------------------------------------------------------------
-----------------------------------------------------------------------------------------------------------------------------------
 ==Interpolating data to create a Raster Surface layer==

@@ Line 53: / Line 53: @@
 ===Loading CSV File and Provincial Boundary File===
-[[File:Screen Shot 2021-12-22 at 10.49.12 PM.png|thumb]]
 * Launch QGIS and create a new project file. Save your project to the folder you created at the start of the tutorial
-# at the top of your toolbar, click the plugin tab and click the "manage and install plugins" item.
+* At the top of your toolbar, click the plugin tab and click the "manage and install plugins" item.
-# In the "all" tab, search for the "QuickMapServices" plugin and install it to QGIS. once this is done restart QGIS
+* Search for the "QuickMapServices" plugin in the pop-up window and install it to QGIS. Save your project, close and re-open the QGIS application to activate the plug-in
-# once you are back into a new project layer, click the web tab at the top and go to the  QuickMapServices dropdown and select oms standard. (this should add in a base map to your project)
+[[File:Plugin 1.png|500px|thumb|left]]
-# we will now add in our 2 layers starting with the weather stations. by clicking on the layer tab at the top of the page go to the "add layer" tab and scroll to the "Delimited Text layer"
+[[File:Plugin 2.png|300px|thumb|center]]
-# in the new window, click the 3 dots at the top right corner of the screen (you will be finding the CVS file that we edited earlier) once you have found it make sure that the "Comma" and "tab" boxes are checked off in the "custom delimiters" file format
-# in the Geometry definition option set your x field to "Long" and your y field to "Lat" so that QGIS knows how to read your coordinates
-# click on the layer tab at the top of the page go to the "add layer" tab and scroll to the "add Vector layer" tab
+* After reopening your project, click the Web tab on the menu, then QuickMapServices dropdown and select OSM standard. This will serve as a base map to your project
-# in the new window, click the 3 dots at the top right corner of the screen (you will be finding the boundary file we downloaded) in the package you downloaded click the file with the .shp end to it and add it to your project
+[[File:Plugin 3.png|300px|thumb]]
-## once it is loaded in right-click on it and select "Open attribute table"
-## once open click the pencil at the top of the window. then select all layers besides Alberta and click the " delete selected feature" tap on the toolbar you clicked the pencil on
+* Add in the monthly climate summary data by clicking on the layer tab in the menu, selecting "Add Layer" and clicking "Add Delimited Text layer"
-## once this is complete correctly you should only have the Alberta boundary file on your project layer (and the weather stations)
+[[File:CSVI 1.png|300px|thumb]]
+* In the pop up window, click the 3 dots at the top right corner of the screen (highlighted in blue in the image below) and navigate to your project folder. Select the climate summary CSV file. In the Geometry definition option set your x field to "Long" and your y field to "Lat" (highlighted in yellow) to set your coordinates
+[[File:CSVI 2.png|300px|thumb]]
+* Click on the layer tab in the menu, go to the "Add Layer" tab and select "Add Vector Layer"
+[[File:VI 1.png|300px|thumb]]
+* In the pop up window, click the 3 dots at the top right corner of the screen (highlighted in blue in the image below) and navigate to your project folder. Select boundary file with a .shp ending
+[[File:VI 2.png|300px|thumb]]
+* Right-click on the boundary layer and select "Open attribute table"
+* In the pop up window, click the pencil (circled in yellow) at the top right of the window to begin editing. Select all layers except Alberta and click the " Delete Selected Feature" tool (circled in red) on the menu
+[[File:AT 1.png|thumb]]
+* Right-click on the boundary and toggle editing to stop editing the layer. Select the "Save your Edits" option from the ensuing pop-up
+* once this is complete correctly you should only have the Alberta boundary file on your project layer (and the weather stations)
 [[File:Screen Shot 2021-12-22 at 10.32.11 PM.png|thumb]]
 # The next step will be to create a permeate layer for your weather station points. to do this right-click on the layer and click export "save feature as"