How to draw circles for locator maps
Sometimes you want to indicate something on a map that's within a fixed radius, e.g. an evacuation radius for a bomb deactivation. A circle is a great way to do so.
There's no in-built tool to create a circle in Datawrapper, and geojson.io also doesn't allow you to draw circles. Luckily, Datawrapper employee Hans Hack built a little tool that allows you to create circles with a certain radius, and then download them as GeoJSONs. You can then easily import them to Datawrapper locator maps.
Here's how that works in detail:
First, go to hanshack.com/geotools/radius. Decide on a radius in m, km, feet or miles; then drag the map around until you got the correct center point. Then click on Download:
Note how the tool takes into account the curvature of the earth. This won't be visible in small circles, but if you place your circle close to the poles or increase the radius, you will see that it becomes taller than wide:
Now that you got your circle, let's create a locator map. To do so, go to app.datawrapper.de/create/map and click on Locator map:
In the very first step, Add markers, click on Import line and area markers. Now drag the GeoJSON file you just downloaded onto the Import GeoJSON or CSV button, or click on it to select the file from your computer. It will now appear in your list of area markers:
Click on the uploaded area marker to style it as needed. You can change the fill and outline color and opacity, add a vignette marker, and much more:
And that's it! Now you got a circle in your locator map.