Mental Maps and The Shadows of Human Impact

I like maps. I like to stare at them, try to figure out what their story is. I especially like maps of the physical environment—I've spent hours on Google Maps' terrain view exploring different areas, trying to read the earth, what the bare ground is telling us.

But even with Google Maps, the roads are still there, still distracting us, still saying "look what humans have created! Look at this mighty road we built in this impossible canyon!" So I went to make my own terrain maps, free of the influence of humans.

My first attempt actually ended up telling more of humankind's story than I intended.

Looking for good-but-not-overwhelmingly-detalied elevation data, I downloaded the 5-meter auto-correlated DEM data for the Salt Lake valley from the Utah AGRC. Auto-correlated elevation models are created examining the differences in stereo image pairs (see https://gis.stackexchange.com/a/61993) and thus show various parts of the built environment. What this means is that my attempt to scrub away humankind was beautifully flawed and ended up showing  some really cool artifacts.

Let's start with freeways, because every post about the evils of human influence has to talk about freeways, right? This is an overpass. Even without showing the roads, the massive amount of earthmoving that's been done to raise one high-volume stream of metal, cloth, and human beings over another stream is a little stupefying.

Even old-school grid systems, the darling child of walkability nerds and new urbanists, get in on the act. They're easier to see when they're cut into a hillside and the streets square off the lots to accommodate our discomfort of weird, unordered shapes.

This is a wonderfully disjointed bit of geomorphology. Freeway planners of the 50s and 60s took advantage of a natural stream channel/canyon to build a freeway without having to tear down homes. The steep canyon walls gradually give way to the valley floor, however, and are replaced by the flat bed and smooth, flowing, engineered curves of the Interstate Freeway system.

For all our love of attacking modern human's impact on the environment, let's not forget that something as Utah-Pioneer-'Merica!-ish as farming shows up as well. This is one of the last center-pivot irrigation fields I could find in the valley, though the latest satellite imagery shows it's been dug up in preparation for some sort of development.

File this one in the "What the ...?" department. A look at the satellite imagery shows this massive, angular cut into the hillside was made for... a park. A park?! I'm sure there's a story and reason behind it, but I can't for the life of me figure it out.

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But the point of this post isn't to tell this micro story, the story of how we've shaped the earth. No, the story I want to tell is this one.

Full-size link (8mb)

Look familiar? This is the Salt Lake valley. I've always wondered what it looked like before 1847, when it the only human inhabitants were the Northwestern Shoshone. Like I said above, it's not perfect, but it still gives us a much better picture of what the land beneath our tires looks like.

The human mind is amazing at creating mental maps of areas. We know the routes that are familiar, the topological links between our house, the roads, the freeway, and our office or favorite shopping center. We know the canyons and tall mountains are "east," that Ogden is "north" and Provo is "south." We recognize the Bingham Canyon Mine slag piles as "west."

But this plays tricks on us as well. For years, I always though of going downtown as "going up" somehow. Looking at the elevation color (AKA hypsometric tint), downtown is lower than most of the valley! My mental map doesn't match reality, and it doesn't even match the word "downtown." But the "downtown is up" concept was so engrained in my brain that in Portland I always thought I was going north when I got off the train at Pioneer Square and walked uphill to the PSU campus... on the south end of downtown. But I was going up!

What I like about this map is that except for the few highly-identifiable freeway cuts and raises, you can't use any of your normal mental map clues to figure out where you are. You have to stop thinking about a home, the road, or an arbitrary address grid coordinate, and start thinking about river channels, glacial moraines, and canyons.

After looking at this map in detail, someone told me they couldn't figure out where was where. That's the point.

As Yoda once said, "you must unlearn what you have learned." Let go of your east side vs west side mentality, your downtown vs suburbs bias, your industrial wastelands vs green-grass dreamworld. Release your a priori knowledge, and see what you can find.

Read the story of the valley.

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I didn't start intending to write about such abstract ideas as mental maps and such conscientious topics as humankind's impact on the world. No, I wanted to share the discoveries I've made in this map of the place I've lived for over twenty years of my life.

Looking at this map, I realize I barely know it.

I meant to write about the cartographic tools and techniques I used, the thrill of getting something to work after trying half a dozen different ways. Someday I'll write that, and the many other techniques I've discovered in the two years since I first wrote this on my personal blog. But for now, I'll keep exploring.