 Hello, in this video I'm going to explain how to symbolize points by varying size. This video is part of a summer course organized for IHG Delft on creating data visualizations with graphs, maps and animations. The tutorial can also be found on GIS OpenCourseWare. You can find the link in the description of this video. I would also like to acknowledge DerkFoods. I have modified his materials for this tutorial. We first go download data from natural earth, great OpenData set. Download the geo package and save it to your hard drive. After downloading, extract the zip file. You can use 7zip.org or the one from Windows. You see by default the windows will create a folder with .geo package which is a bit strange for a folder name and will not work in QGIS. So you have to rename the output folder and let's call it summer course where we will store all the data for the summer course and subfolder population. Click extract to unzip the files and folders. And here we see the result and under packages you can then find the geo package. So let's go to QGIS and there browse to the folder where we just extracted the layer and make it a favorite so we can easily go to our summer course folder also for the next tutorials. And there we find the geo package and we drag it to the map canvas. And there we are going to select the layers that we are going to use. We are going to use a polygon layer with the countries. And choose a one that also has the lakes. And the second layer, if we keep our control button pressed we can select the second layer is population layer with the cities, populated places layer. And then we click add layers to add it to the map canvas. And there are the layers. Make sure that your points layer is on top. The general order of layers in the layers panel is first points then lines, then polygons and then rusters. Now we're going to focus on styling the countries. So uncheck the points layer and go to the styling panel. Make sure that the countries layer is the target layer. And then let's first change the color by clicking on the color bar. You can change colors easily by using these sliders or you can type the RGB color code. In this case we will use 200, 200, 200 for red, green and blue which will give a gray value. Tell me how this works. If red, green and blue are zero we get black. If they are 255 we get its color as you can see here. So if B is 255 it turns into blue. And if they're all 255 it's white. And every value in between and if it's the same value would give a gray tone. Let's go back, click on simple fill and there we can also change the stroke color. And let's change it from black to white. So as we learned we use 255, 255, 255. So now we have a nice background layer that is subtle because it is low in the visual hierarchy. Let's focus now on the main layer that is going to convey our message. That's the point layer so make sure that it is the target in the layer styling panel. Then change the renderer from single symbol to graduated. And use for value the pop max field which contains the population of the cities. Change the method to size. Click classify to apply. We see that the population numbers are very high and large numbers and it's much. Better to express this in millions. So we're going to calculate the population per million. So we divide it in the expression dialogue by a million. Click OK to close the dialogue. And click classify to apply the expression. I'll click on the symbol to change the properties. Let's first change the color from the random color that was assigned to a nice purple color. And we use here the RGB and the 31, 99 and 236. We'll also use 50% opacity. So opacity is the opposite of transparency. Let's go back. For now we have used the equal count or quantile mode which gives a bit strange borders. Let's go for pretty breaks which gives nice rounded numbers. You can also play with the trim setting to change the precision value for the decimals. But here we keep the trim checked. You can also see that the smallest circles have outline that is almost as big as the surface of the area of the point. So we're going to change this by removing the lines from the smallest point. So we choose no pen. Go back. Now let's change the ranges of the size from 1 to 12 to make it a bit bigger and nicer. But you see when we change this setting we also use the outlines for the other circles than the small ones. So we need to set that back. Make sure they're not selected and then go back to change it to solid line. And then again click on the smallest circle and under simple marker change that one back to no pen. So we now have again that the smallest points have no outline and the larger ones have. Until now we have been using the geographic coordinate system for this project. Let's change this to an equal earth projection that preserves the proportion of surface areas. At filter type equal earth to see which projections we can choose from. You see that there are different choices here based on where you want to center the projection. Let's choose the one for green ridge. You also see that there are some providers from S3 but we will use the EPSG code. Now the background is white and it would be more realistic to have a nice ocean color there. So let's add from the gel package a layer which has the ocean. Here's one and drag it to the map canvas. It will also get a random color so let's change the fill color to something that looks more like an ocean but we still keep it a bit subtle. So we're going to choose some blue. We'll start from blue and then use the sliders to modify this to something that looks nice. Go back and under simple fill also remove the stroke color by choosing for stroke style no pen and then of course the ocean layer needs to be at the bottom. It's helpful for the user if they see some labels for these cities so we're going to add some labels. Make sure that the places layer is the target layer in the layer styling panel and go to the labels tab. Change to single labels and we use the name field by default but you see it's super crowded in the map so we need to make some adjustments there. Let's first change the font to a Calibri which is Sansarif font and we change the size to 13. Then we can improve the readability by using a text buffer and we make a size of 0.5 millimeters and we use the same color as we used before the C8C8C8 which we can also type there that's a hexadecimal code that we can also use to configure the colors and you can see that that's equal to RGB 200 200 200 as we said before. This gives us subtle background buffer but there's still too many places here. Now the map is still too crowded so let's do something about it. Let's go to the rendering tab and there we check the box to show all labels for this layer including colliding labels. This of course makes it worse but if we then under show label go to the data defined override we can add an expression to only show the places that are larger than a certain size. You can play with that value so look for pop max under fields and values double click to add it to the expression type larger than and then here we will use 10 million so only cities that are larger than 10 million will be shown and that very much improves our visualization here. So we can change the settings to better place the labels but here we're going to do that manually and you see here that labels toolbar with buttons to adjust the labels so we can move labels by clicking this button and when we click on a label it will first ask us for a primary key we keep it as a default and then we can start moving the labels by clicking on them and dragging them to the position where we want them. Make sure the labels are as least as possible crossing boundaries and that it's still clear to which city they point so bring them close together.