Hello friends! And Happy New Year 😊 We finally made it, and I’m looking forward to a clean slate to start off the year. Taking December off of blog posting let me take a much needed break from a busy mind, and I feel a little more recharged and ready to start thinking about maps again.
Last we left off, I believe I was about to dive into some of my new favourite tools in QGIS that are very simple, and very useful basics to have in your toolbox: importing and mapping lat/long point data, joining data, and creating overview maps.
Importing point data
Sometimes, the only data that may be available is an excel spreadsheet or CSV that has latitude and longitude info. I knew how to do this in ArcGIS, but I had to look it up for QGIS. Turns out, it’s pretty simple…
In the layer menu, you can select adding a delimited layer (see image above). From here, a window opens where you can select your CSV (make sure you’ve converted from excel to CSV), name the layer, select the latitude (Y field) and longitude (X field), and coordinate reference system (CRS). For most latitude and longitude data, the WGS84 coordinate system is the CRS you will need to choose. I have it selected in the blue rectangle below (EPSG:4979 – WGS84).
Selecting add will create a projected layer in your open QGIS project, but keep in mind, the layer is not saved externally from this project yet. You can right click on the layer and export it to save it for use another time.
Joining data
In QGIS, joining data is only slightly different than in ArcGIS. As a quick reminder: joining is used when you have two data sources that you want to combine. Usually, both datasets will
have one attribute in common, such as an ID number as we saw in the Beans Pt. 2 post with the CDUID identifying code. This shared attribute is used to correctly assign data from a new dataset to the original dataset. In
Arc, usually you can join by right clicking on the layer you want to join data to, but in QGIS, you need to go into the properties window of the layer you want to join data to and find the Join tab. Then you click on the green plus sign and continue as normal, selecting the new dataset and the name of the shared attribute for both datasets (see images to the right). In addition, you can select which specific attributes from the new dataset you want to bring in and designate a prefix for the joined attributes (I recommend doing this). I really like the level of control and naming options that QGIS gives the user, which is something that Arc lacks to some degree.
Overview maps
Finally, overview maps! These are super useful for showing your audience where your case study is located on a larger map, which is especially useful if they are not familiar with the area. See the example I have provided, which shows the lower half of Ontario, and the highlighted area on a full map of Ontario.
On your map layout window, draw a smaller new map on top of your map (see outlined in red in image below), make this map as zoomed out as you need. Then, with the new map selected, go to the item properties tab and scroll down to Overviews. Here you can add a new overview (green plus sign), select the original map as the map frame, and choose a colour and style for your overview.
That’s all I have for you this week! I hope these tips are helpful to you in your mapping journey, whether you are trying mapping for the first time, or transitioning from ArcGIS to QGIS like I did.