Digitizing and Georeferencing in QGIS - Revision history

Nata Culhane: /* References and Resources */

2023-09-25T18:48:11Z

References and Resources

Nata Culhane: /* Tutorial for Digitizing with QGIS */

2023-09-20T17:48:29Z

Tutorial for Digitizing with QGIS

Nata Culhane at 17:34, 20 September 2023

2023-09-20T17:34:52Z

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Nata Culhane at 17:25, 20 September 2023

2023-09-20T17:25:23Z

Nata Culhane at 17:24, 20 September 2023

2023-09-20T17:24:59Z

Nata Culhane: /* Software */

2023-09-20T17:19:14Z

Software

Nata Culhane at 17:01, 20 September 2023

2023-09-20T17:01:27Z

Nata Culhane: /* References */

2023-09-20T16:50:54Z

References

Nata Culhane: /* Tutorial for Georeferencing with QGIS */

2023-09-20T14:52:54Z

Tutorial for Georeferencing with QGIS

Nata Culhane at 14:48, 20 September 2023

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 USGS. (2023). What does ‘georeferenced’ mean?. USGS. https://www.usgs.gov/faqs/what-does-georeferenced-mean#:~:text=Georeferencing%20means%20that%20the%20internal,ground%20system%20of%20geographic%20coordinates
 * More information about georeferencing and its uses
+[[Digitizing_in_QGIS|CUOSG Wiki - Digitizing in QGIS]]
+* Another tutorial from the CUOSG Wiki that gets into more advanced digitizing - a great resource to look into once you've gotten the hang of the basics from this one!

← Older revision		Revision as of 17:48, 20 September 2023
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	Digitizing is one of the most frequent duties assigned to a GIS Specialist. Often, a significant portion of GIS effort is spent digitizing raster data in order to create vector layers for analysis. QGIS includes robust on-screen digitizing and editing features, which we shall investigate in this section of the tutorial.		Digitizing is one of the most frequent duties assigned to a GIS Specialist. Often, a significant portion of GIS effort is spent digitizing raster data in order to create vector layers for analysis. QGIS includes robust on-screen digitizing and editing features, which we shall investigate in this section of the tutorial.


	* Go to Layer > Add Raster Layer. Locate the georeferenced image and click Open.		* Go to Layer > Add Raster Layer. Locate the georeferenced image and click Open.

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 In this example, Carleton University was located on Google Earth Pro (see Figure 1 below).
-[[File:Figure 1.jpg|frame|center|Carleton University's campus was located on Google Earth Pro, to be used as the example data for this tutorial]]
+[[File:Figure 1!!.jpg|frame|center|Carleton University's campus was located on Google Earth Pro, to be used as the example data for this tutorial]]
 Once you are happy with the location you've selected, go into the options panel > navigation > make sure that 'do not automatically tilt while zooming' is checked. As well, in the main menue, turn off terrain. This will ensure that your image is flat and easy to work with in QGIS.

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 == Introduction ==
-This tutorial will demonstrate georeferencing and digitizing features in QGIS, using imagery downloaded from Google Earth Pro. Georeferencing is the process of taking a digital image, air-photo, or scanned topographic map, and using spatial data or coordinates to locate the image in the real world using GIS software (USGS, 2023). Essentially, georeferencing ties an image to the coordinate system used on earth, allowing for digital map analysis (point-and-click for coordinates, calculate area and distance, etc) (USGS, 2023). It links known reference points to the earth in order to georeference the entire image. Digitization is a process where geographic data in a hardcopy or a scanned image form is converted into vector data by tracing the features as either points, lines, or polygons, to convert georeferenced data to a digital format, such as a shapefile (ArcGIS Developers, 2023). Both digitizing and georeferencing are useful skills to learn, as they allow users to easily determine real-world spatial information from an image, such as knowing coordinates and distances. They are also always the first processes when analyzing a scanned or hardcopy map, so they are good basic skills to master.
+This tutorial will demonstrate georeferencing and digitizing features in QGIS, using imagery downloaded from Google Earth Pro. Georeferencing is the process of taking a digital image, air-photo, or scanned topographic map, and using spatial data or coordinates to locate the image in the real world using GIS software (USGS, 2023). Essentially, georeferencing ties an image to the coordinate system used on earth, allowing for digital map analysis (point-and-click for coordinates, calculate area and distance, etc) (USGS, 2023). It links known reference points to the earth in order to georeference the entire image. Digitization is a process where geographic data in a hardcopy or a scanned image form is converted into vector data by tracing the features as either points, lines, or polygons, to convert georeferenced data to a digital format, such as a shapefile (ArcGIS Developers, 2023). Both digitizing and georeferencing are useful skills to learn, as they allow users to easily determine real-world spatial information from an image, such as knowing coordinates and distances. They are also always the first processes when analyzing a scanned or hardcopy map, so they are good basic skills to master. Extra tutorials and readings on this topic are linked in the References and Resources section for your convenience.
 The first section of this tutorial will focus on georeferencing, starting by downloading Google Earth imagery and reference points, then bringing these into QGIS and starting the georeferencing tool, tying reference points to the image, and finally producing the finished georeferenced file. The second section of the tutorial will use the georeferenced image from part 1 to explain basic digitizing skills, creating point, line, and polygon shapefiles from the image.
@@ Line 7: / Line 7: @@
 == Software ==
-Georeferencing can be done in a variety of GIS software. Here, QGIS is used. Quantum GIS (QGIS) is a free, open source software (FOSS) that allows users to interact with geospatial data and analysis tools similarly to with more advanced programs. It supports various datasets such as vector and raster, several plug-ins and database formats, and lets the user browse and create map data on their computer. This tutorial also uses Google Earth Pro, which is another free program that allows users to create point KML files, download images, and even do simple map analysis (calculate distance, etc).
+Georeferencing can be done in a variety of GIS software. Here, QGIS is used. Quantum GIS (QGIS) is a free, open source software (FOSS) that allows users to interact with geospatial data and analysis tools similarly to with more advanced programs. It supports various datasets such as vector and raster, several plug-ins and database formats, and lets the user browse and create map data on their computer. This tutorial also uses Google Earth Pro, which is another free program that allows users to create point KML files, download images, and even do simple map analysis like calculating distance.
 == Data ==
-The first step is to locate a suitable historical image to georeference. These can be found in many places online, but in this tutorial it was obtained from Google Earth Pro. Regardless of where the data is obtained from, it is essential to also download or create reference/ control points to go along with the image. These points are what will be used later to actually georeference the image.
+The first step is to locate a suitable historical image to georeference. These can be found in many places online, but in this tutorial, it was obtained from Google Earth Pro. Regardless of where the data is obtained from, it is essential to also download or create reference/ control points to go along with the image. These points are what will be used later to actually georeference the image.
 In this example, Carleton University was located on Google Earth Pro (see Figure 1 below).
-[[File:Figure 1!!.jpg|frame|center|Carleton University's campus was located on Google Earth Pro, to be used as the example data for this tutorial]]
+[[File:Figure 1.jpg|frame|center|Carleton University's campus was located on Google Earth Pro, to be used as the example data for this tutorial]]
 Once you are happy with the location you've selected, go into the options panel > navigation > make sure that 'do not automatically tilt while zooming' is checked. As well, in the main menue, turn off terrain. This will ensure that your image is flat and easy to work with in QGIS.

@@ Line 7: / Line 7: @@
 == Software ==
-Georeferencing can be done in a variety of GIS software. Here, QGIS is used. Quantum GIS (QGIS) is a free, open source (FOSS) GIS system that allows users to interact with geospatial data and analysis tools similarly to with more advanced programs. It supports various datasets such as vector, raster, several Plug-ins, and database formats and lets the user browse and create map data on their computer. This tutorial also uses Google Earth Pro, which is another free program that allows users to create point KML files, download images, and even do simple map analysis (calculate distance, etc).
+Georeferencing can be done in a variety of GIS software. Here, QGIS is used. Quantum GIS (QGIS) is a free, open source software (FOSS) that allows users to interact with geospatial data and analysis tools similarly to with more advanced programs. It supports various datasets such as vector and raster, several plug-ins and database formats, and lets the user browse and create map data on their computer. This tutorial also uses Google Earth Pro, which is another free program that allows users to create point KML files, download images, and even do simple map analysis (calculate distance, etc).
 == Data ==

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 [[File:Figure 3!!!.jpg|frame|center|Creating a folder of reference points in Google Earth Pro]]
-Finally, you are ready to export your image and reference points. To save the reference points, right click the folder> save place as > and ensure you are saving a KML file. To save the map, make sure all points are visible in your view, then go to file> save> save image. Turn off extra map options (like the title, etc), and choose the highest file size. Save as a JPEG.
+Finally, you are ready to export your image and reference points. To save the reference points, right click the folder> save place as > and ensure you are saving a KML file. To save the map, make sure all points are visible in your view and the compass is oriented to north, then go to file> save> save image. Turn off extra map options (like the title, etc), and choose the highest file size. Save as a JPEG.
 == Tutorial for Georeferencing with QGIS ==
@@ Line 129: / Line 129: @@
 [[File:Figure 11!!.jpg|frame|center|Complete digitized files]]
-== References ==
+== Conclusion ==
+In this tutorial, you have learned how to:
+* Download reference points and imagery directly from Google Earth Pro
+* Use QGIS to georeference Google Earth imagery
+* Use QGIS to digitize georeferenced files
+== References and Resources ==
 ArcGIS Developers. (2023). Geo-Referencing and Digitization of Scanned Maps. ArcGIS. https://developers.arcgis.com/python/guide/geo-referencing-and-digitization-of-scanned-maps/
+* This page includes more advanced georeferencing and digitizing tips specific to scanned maps
+GIS University. (n.d.). Georeferencing in QGIS. GIS University. https://gis-university.com/georeferencing-in-qgis/
+* This tutorial follows similar procedures to those encountered in this tutorial, but is more specific to georeferencing scanned paper maps.
 Q-Tips. (2018, October 10). QGIS Georeferencing Google Earth Images. [Video]. YouTube. https://www.youtube.com/watch?v=RjkZgE_WVBk
+* This tutorial follows similar procedures to those encountered in this tutorial, and may be useful for more visual learners.
 USGS. (2023). What does ‘georeferenced’ mean?. USGS. https://www.usgs.gov/faqs/what-does-georeferenced-mean#:~:text=Georeferencing%20means%20that%20the%20internal,ground%20system%20of%20geographic%20coordinates
+* More information about georeferencing and its uses

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 * Fill in the transformation settings dialog as shown in the figure that follows.
+[[File:Figure 5!!.jpg|frame|center|Transformation settings dialog]]
-[IMAGE!!]
 If you would like to see that the georeference worked, you can preform a quick test:
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 [[File:Figure 7.jpg|frame|center|Testing that georeferencing worked]]
 ==Tutorial for Digitizing with QGIS==

@@ Line 95: / Line 95: @@
 [[File:Figure 7.jpg|frame|center|Testing that georeferencing worked]]
-==Digitizing tool==
-Digitizing is one of the most frequent duties assigned to a GIS Specialist. Often, a significant portion of GIS effort is spent digitizing raster data in order to create vector layers for analysis. QGIS includes robust on-screen digitizing and editing features, which we shall investigate in this course.
 ==Tutorial for Digitizing with QGIS==