The text provides a comprehensive guide to top open-source GIS software. It emphasizes on the prominence of ArcGIS and QGIS in the field, and delves into various aspects like keyboard shortcuts, adding base maps, creating new layers, editing features, symbology, using the toolbox, field calculator, adding labels, map themes, and map layout. It culminates with encouragement for readers to explore and expand their skills in spatial analysis and cartography using the provided fundamentals.
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A comprehensive guide to the best open-source GIS software
More than 10 years when I started my data career as a GIS (Geographic Information System) analyst, two pieces of do-it-all GIS software were prominent. 10 years later, it is still the same two software. ArcGIS by ERSI is by far the dominant king, which is very easy to use with many features and an excellent Python library that came with it. However, it costs money and only works on Windows.
QGIS (Quantum GIS) on the other hand is the best open-source alternative. It ships to most operating systems and has a very active open-source community. You won’t do wrong committing to either software, but as I went deeper into my programming career, using Windows became more difficult, and I generally tried to avoid enterprise software to avoid any procurement administrative work. Hence I deviate more towards QGIS now.
What You Will Learn
At the end of this walkthrough, you will learn how to make a map like this, which I will use for a forest survey.
Keyboard Shortcuts
There are a few commonly used actions whereby implementing keyboard shortcuts that will make your life easier. I will customise them so they are easier to reach. This might seem unimportant, but trust me, it just optimises everything when you want to move and toggle around your mapping project.
Add a Base Map
The base map is the background of your entire mapping project. We usually use authoritative maps as the background to get a sense of the land details when we add our layers on top of it. In QGIS, base maps can be added by first installing the plugin at Plugins > Manage and Install Plugins > QuickMapServices. These maps are retrieved via external APIs, so an internet connection is required.
Create a New Layer
There are two types of graphics used in GIS. The earlier Google satellite imagery was made up of a grid of colour pixels, and this is known as a raster. This has a resolution where if you zoom in enough, will eventually see the individual pixels.
Adding a Feature
It is quite straightforward to create a feature, in this case, a polygon. We just need to select the layer on the menu, enable the Toggle Edit (pencil icon), and then the Add Polygon icon. Then, we point our mouse over the base map and trace a polygon over the area by clicking on it. Finally, when we are done, we can right-click, and a popup will appear, prompting us to enter the attributes for the feature into the attribute table, if required.
Editing a Feature
There are many types of editing existing features, and in this instance, I will show how to split an existing polygon into parts. First, as before select the layer and Toggle Edit. Then go to Edit > Edit Geometry > Split Features.
Symbology
To adjust a layer’s fill and border colours, we can right-click a layer > Properties > select the Symbology tab. If the features in the layer have a category or numerical scale assigned in its attribute table, we can also change the colour display from Single Symbol to Categorized or Graduated.
Using the Toolbox
The processing toolbox contains all the possible spatial processing for your work. And they can be accessed at Processing > Toolbox, with a simple search box to get whatever you need. In this case, we want to create some stratified random samples by adding random points within each survey area.
The Field Calculator
We talked a little about the attribute table earlier, which is a table in a shapefile or layer, where every feature can have corresponding data stored in it. With the spatial attributes of the features in the layer, we can do calculations in the table using a Field Calculator. In this instance, we want to create two new fields X and Y in the attribute table of the random points showing their coordinates.
Adding Labels
Now that we have the X and Y coordinates created for each point, how can we display them on the map? This is done by turning on the labelling options from the toolbar (or right-click the layer > Properties > Labels). We then select the layer > Single Labels > and click on the expression dialog to craft how the label should look like.
Map Themes
Map themes are important when within the same project, you want to display different layers and do not want the hassle of switching them on and off. Themes are also important when we are creating multiple maps within the same map layout as you will see in the next section, where we need our main map, as well as an inset.
Map Layout
The final part is to add all the necessary items to make it a proper map. This is done by creating a layout.
Summary
Spatial analysis and cartography is a niche field of data analytics and visualisation. In the years when I worked in this field, I have created maps for display in the public and published in magazines, books and journals. It was a fun and interesting endeavour, and I believe you can do the same with the fundamentals I provided above and expand from there.
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