Thread by @ron_halliday

I might be the last one on the population flag map bandwagon, but I’m pleased with the result! Thanks to @StatCan_eng @StatCan_fra for providing nearly *half a million* polygons to select from.

#cartography #gischat #QGIS #canada @CanadianGIS @GANSorg

(Details in the thread.)

Over the last couple of weeks people have been posting their population flag maps, so I thought I’d try my hand at creating one for Canada. I figured that with detailed census data, I might even be able to include a reasonable facsimile of the maple leaf.

So I went to download the boundary file of Canada’s 56,589 dissemination areas, the smallest geographic area for which full census data is provided. That’s when I discovered that Statistics Canada also provides a 'dissemination block' boundary file.

Dissemination blocks are much smaller than dissemination areas. However, to protect the privacy of Canadian citizens, only the population data is made public. Since that's all I really needed anyway, I downloaded a 476MB shapefile containing a staggering 489,676 polygons.

Rather than creating a two-colour 50/50 population map, I decided to reflect the proportions of the Canadian flag. As such, the left and right bands represent 25% each, and the maple leaf a little less than 13.7%. The remaining 36.3% would be white.

The left band was easy enough, since the combined population of British Columbia, Alberta and Yukon Territory turned out to be something like 24.9%. So I just had to include part of the Northwest Territories to top it off. Success!

The right band wasn't too complicated either. I started by selecting all the blocks east of 70° W and all the blocks between the Saint Lawrence River and the 45th parallel. Then I topped it off by adding a thin buffer along the north side of the Saint Lawrence.

The maple leaf 🍁was a lot of fun! By fun, I mean trial and error. It was clear that the only place where I could find 4.8 million people and maintain its shape was in the Greater Toronto Area, so I scaled and rotated the leaf until it did just that. And it *barely* fit. 😌

Then I made a coffee and went to work searching for the perfect combination of dissemination blocks so that there would be exactly 8,787,929 people represented in each red band and 4,814,868 people represented in the maple leaf. Because accuracy!

Finally, I pruned some unsightly blocks along the edges of the red bands – but only when the population of the dissemination block was zero, like in Northern Canada and Quebec.

Now for the fun part: making the map!

Statistics Canada provides boundary files in their Lambert Conformal Conic projection, so I kept it for the map. Then I went about adding some flavour, including part of the flag’s royal proclamation using a font quite similar to the document’s handwritten calligraphy.

And there you have it! Everything was done in QGIS 3.14.15, except for a small touch-up of the drop shadow.

So yeah, last on the bandwagon, but at least I finished it before the 2021 census.