Projections are a hard concept for students. Fundamentally, they understand that to represent the round earth on flat paper (or a flat screen), something’s got to give. We talk about developable surfaces, and distortion, and why it’s important to project data layers correctly for analysis and visualization in our foundations course, and in almost every course after that, there are a number of students who still seem to miss the point.
“But my GIS software just draws everything together, regardless of projection, so why does it matter?”
“But I projected my data, why does my map still look wrong?”
“But it is projected – it’s in WGS1984!”
I will never have the deep understanding of projections that my NACIS colleagues Bojan Šavrič and Tom Patterson wear like a badge (or at least a t-shirt). But projections are a fundamental part of what we do as spatial researchers and cartographers, so everyone needs to know at minimum that choosing the right projection is important to measurement, navigation and aesthetics.
How do we teach students about projections and why they matter?
There are some fun videos out there that cut up globes, or flatten oranges, which gets them thinking about the challenges of representing the round earth on a flat surface, but not so much about the distortion in a specific area. Others have projected the human head in multiple ways, to help them understand the distortion, but mostly students wonder why the heck you’d do that, because they are obviously all wrong, rather than understanding the relative strengths and weaknesses of each projection.
They seem to get the idea that distortion happens, and that we mainly want to control it in our area of interest (also known as making it somewhere else’s problem). But they’re not quite to the point of making a solid connection between why you’d use one particular projection over another.
How do we get students to think about choosing the right projection for the job?
This is a trickier question, and I’d love to hear what the rest of you are doing. I used to use one that outlined a few scenarios for students to create a basemap (e.g. need a map of the Andes region that preserves shape, or need a map of the contiguous US that preserves area), and have had mixed results. Often, students are trying to use projections designed for the whole world, and then just moving a central meridian or standard parallel. Not unworkable, just not ideal for areas smaller than a continent. Recently, I switched to a small multiples version, using the same country (China) throughout, and having them thoughtfully compare 6 different projections, modified for that part of the globe. Initial results look promising, but we’ll see if that carries forward into other assignments where they have to decide for themselves how to flatten that part of the earth.
We have some fantastic students who come through our program and win awards and go on to do great things with maps. But I want to reach a larger percentage of them, and I want to stop looking at maps of the US in Web Mercator.
I understand if you nodded off somewhere in the first paragraph. If you made it this far, thanks for reading what amounts to a little bit rant, a little bit call for help. I’d love your thoughts on how you teach projections.
Here are some resources I’ve been sent since posting this (more as they are suggested):
Define Projection or Project?, a nice post that adds some clarity on the Define Projection tool in ArcMap/Pro by Heather Smith
A nice post (with hand-crafted artwork!) on coordinate systems, with a side order of Plate-Carrée, by Lyzi Diamond