Recently, I made a map for some colleagues who were giving a presentation, and the image received a lot of praise (or at least, that’s what they told me when they got back). One feature that caught the most attention was that the study region stood out slightly from the rest of the country. This is a very easy trick that basically requires making everything except your region slightly more opaque. Let’s start with a GTOPO30 DEM of central Europe, then show how we can highlight the country of Hungary for a general overview map:
Hopefully you already have a basic polygon shapefile of the country (or a larger administrative region) within which you are working. If not, very coarse political boundaries are available for free from the GADM database (www.gadm.org). Then, follow the steps below:
- Create a basic outline of your study region – a polygon shapefile is best. Alternatively, select one of the polygons from the GADM shapefile and export it as its own file (right-click on the file name in the table of contents, then navigate to Data \ Export Data).
- Next, use the “Erase” tool (Analysis Tools \ Overlay) to cut the shape of your study region from the larger country polygon (I like to think of this tool as a digital cookie cutter!).
- Add the new file to your session and rearrange the order of the layers as follows, changing the symbology settings for each:
- Large administrative polygon – outline should be dark, with no fill
- Study region polygon – outline should be dark, with no fill
- Large administrative polygon with study region removed – no outline, white fill. Use the “Display” tab to set the transparency to between 50-80 percent, depending on your preferences.
- Add a DEM or other base imagery below these layers. Voila!