I shade, you shade…

So I’m a Tom Patterson fan girl. He probably doesn’t remember this but a few years ago my husband and I were on vacation making the rounds to Annapolis, MD, then D.C., then stopping over at Harper’s Ferry on the way home to meet a friend of ours who was a cartographer for National Parks. We met her at the National Park office and she introduced us to Tom Patterson and his young understudy (whose name I regrettably cannot remember, but he was a genius.)

Tom and this other guy work out of a tiny little closet-of-an-office. With the four of us crammed in there together, he was gracious enough to basically give us a crash course in how he made his world-famous hillshades. I was slack-jawed the whole time watching them run through masking and shading and all sorts of little tweaks with a fine, refined muscle memory that only comes with expertise and time. These hillshades are a beautiful work of art. I don’t mean that in the superficial “oh, they’re really pretty” kind of way. I genuinely mean it’s a work of art. They are manipulating the viewer with their subtleties and nuance. They build a whole other dimension of experience for park guests… one that I would argue is just as important as the experience of visiting the park itself.

People collect National Park maps. Other than a t-shirt, mug, some iPhone snapshots or other typical tokens, the park map is one of those things that goes home with a wide variety of visitors and is really cherished. If other households are anything like ours (and, ok, with two botanists who do GIS living under one roof, perhaps your house isn’t QUITE like ours), you may have a drawer or corner of the bookshelf dedicated to the maps you’ve collected on your travels. No? Just us?

Anyway. Ever since Tom’s crash course, I have personally been DYING to make some pretty maps. I rarely get the opportunity. Most of what I do is editing, data management, or quick maps for meetings, etc. One of the highest compliments I ever received was on a mock-up map I made for a hypothetical park plan. My Deputy Commissioner commented “It makes me want to GO there!” That’s what park maps SHOULD do for people.

Ok – I digress. Where was I? Oh yea- I don’t often get to make pretty maps. Recently, we got a new machine at the house and I was dying to try it out a little bit. We also have fresh LiDAR for East TN and likewise, one of my favorite park managers challenged me to come up with some fun ways to visualize their trail data. Well, I got sidetracked with the hillshades and some raster functions. Inspired largely by the ESRI multi-directional hillshade (which I am convinced was inspired by Eduard Imhof), I came up with a handful of hillshades, two of which I’ll share here:

This first one was a multi-directional hillshade. I’m not entirely sure I worked the formula correctly, but it is what it is… Derived by taking the square root of the product of three hillshades run at three different azimuths. The shading was just tweaked in various ways until I got something I kind of liked. I liked the moodiness of this particular hillshade. The sepia tone gives it an old-school look while the contrast gives it an eerie feel. However- it’s not very practical and wasn’t playing well with my functions, so I then played with just a single hillshade and straight-up raster functions for pansharpening:

Here’s the result of that… A lot cleaner and a lot more practical. The LiDAR detail makes my heart thump and the color ramp is subtle but does the job. I kept the park boundary overlay pretty subtle and used a multi-ring buffer to feather it. Our park boundaries never are very pretty and I hesitate to alter them for aesthetic reasons because I don’t want folks to get up in arms. So I just try to hide them without hiding them. I slapped on the trails layer with a simple marching-ant-esque line and extracted (incompletely) the watercourse. Overall, I’m pretty happy with this hillshade. The technique with raster functions is quick and I love that you can save a string of functions if you like the result.

I imagine if I were Tom Patterson I’d probably feather out some of the detail from outside the park boundary, emphasize some of the more prominent features within the park and otherwise do some amazing tweaks to make this thing look less homogenous across the surface and make your eye move around the  map. BUT, without Natural Scene Designer, expensive plugins for Adobe and other fun stuff, this is what I’ve got!   : )

P.S. I’m always curious about people’s reactions: To contour or not to contour? Personally, I think the human brain is wired to understand intuitively that the shading is giving depth and we can perceive “steepness” just fine without contours. Likewise, I have found that most people don’t even know how to read contours but they like the “mapiness” of it. So unless specifically requested, I typically reserve use of contours for report maps and not public-pretty maps. But – just an opinion!



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