I’m constantly assembling, in my mind, a toolkit built out of little tricks that I see other cartographers pull off. I take pleasure in the small things. The big picture is important, and certainly we need to focus on telling a clear story that looks great, but it is the details that always interest me most: a well-done coastal effect, great typography, or a smart tweak to an old, standard symbology.
In that spirit, I’d like to take a minute to promote a couple of nice ideas which come from the Historical Atlas of Canada. Geoffrey Matthews served as the Cartographic Editor for its three volumes, the last of which was published in 1993. During my introductory cartography course, the instructor pointed to it as an example of one of the final great works of the manual cartography era, and I have found things to appreciate in it ever since.
There are three nice things I’d like to share…
“In-situ insets” is a term I just made up to explain what’s going on above. Maybe it has a real, accepted term already. Perhaps you could call it “lensing” instead? It is as a magnifying glass, dropped over the terrain. Instead of separate inset maps that zoom in on areas like Vancouver or Toronto, the authors expand these areas and then plop them right down in the middle of the map, covering part of the basemap. For comparison, here’s a map of Canada all at the same scale that I swiped from Wikipedia.
Admittedly, the geography of Canada helps the authors here. There’s not much going on nearby that needs to be shown for the stories they’re trying to tell, so it can be safely covered up. Creating in-situ insets requires some fortunate circumstances, but when they come together, I think it’s a fabulous idea. I think forcing people’s eyes to shift to a separate inset map is disruptive and reduces their appreciation for the spatial context you’re trying to show. Keeping everything in one place, on one map, is more coherent.
Sometimes, instead of an in-situ inset, the authors do something like this:
The greyed out section of the main map and the arrow to the inset create a strong, nice-looking connection. So often, when we want to make an inset map, we end up putting it in a box, separated from the main map by a line. But I’m wary of introducing extra dividing lines into a map layout; I think it’s done way too often, and it prevents the various page elements from being seen as a coherent whole. The setup above is a nice way to have an inset without having to separate it from the main map. It is seen more clearly in its spatial context.
I’m not sure how I feel about the extruded, pseudo-3D perspective, but I expect this idea would work just as well in 2D.
Gridded Proportional Symbols
Finally, something nice that has nothing to do with insets. I like the Historical Atlas of Canada‘s use of proportional symbols that are gridded, so that they can be be easily broken down into countable units. Here’s an example:
In many maps, these would simply be treated as proportional squares or lines, but in the Atlas, they’re broken up into units (I’ve seen the New York Times do similar). So, a reader can look at the whole and make a quick comparison, or they can take a moment to actually start counting if they’d like to dig out the actual number. Normally it’s very difficult for a reader to get an estimated value from a proportional symbol, but the grid makes it much easier. I like to call these “aggregate symbols,” as they’re proportional symbols built out of many individual pieces.
Here’s a second example, which we saw in the last section:
This map takes things a step farther and color-codes the units, adding another layer of data that, importantly, doesn’t interfere with the big picture. If you want to see the overall pattern, you can just look for the tallest stacks. If you want to dig deeper, more data are there, but they’re not in the way. It can be read at multiple levels, which is quite an excellent goal to aim for.
So there you go! A few nice tricks from a great product. They’re little things, but I think that small details is what a lot of good mapmaking comes down to.