Designer’s Field Guide

Tim’s Theory of Trails

A conceptual model for terrain

Tim Sheiner
8 min readDec 4, 2023
Image of a peaceful path through lush woods

I used to spend a lot of time running trails.

And — because I liked to explore new territory — I also spent a lot of time at unfamiliar trailheads staring at a map displayed on the parking lot kiosk, trying to memorize which trails to follow to run a loop. Once on the move it was hard to connect the image of the map in my mind with the actual terrain I was running through and make the correct decisions where trails crossed. I was fit enough back then that making a mistake and having to run a mile or two more than I’d planned usually wasn’t a problem, but nonetheless, I didn’t want to get lost.

My solution to this regular challenge was to develop a model of how trails & terrain interact that enabled me to work out a route on the fly through a network of trails I hadn’t run before. I gave this thing the somewhat grandiose name Tim’s Theory of Trails because I noticed that once I’d come up with it, it gave me a kind of superpower: not only did it help me avoid getting lost on a trail run, it gave me a way to orient myself in any kind of unfamiliar terrain. The distinction is that not getting lost is a practical, rational experience of getting from A to B on the planned route in the expected time frame. Being oriented, however, is an emotional experience, a kind of well being that comes from being confident about the relationship between your origin, destination and current location in terms of the terrain you can see around you.

Not getting lost is getting from A to B on the planned route in the expected time frame.

Being oriented, however, is an emotional experience.

Nowadays I still spend a lot of time on trails (albeit moving at a much slower pace) and, of course, I no longer have to remember routes because I have GPS apps on my phone. However, I find — and I think anyone who travels trails a lot would agree — that while these apps make not getting lost trivial, they are poor at providing a sense of orientation. Therefore, for those who would appreciate a method for orienting to the physical terrain around them and being able to visualize the kinds of trails, grades and decisions they will encounter as they proceed, I offer here a complete description of Tim’s Theory of Trails.

Tim’s Theory of Trails

The theory is simple, it has only two parts.

1. The earth is made up of ridges and valleys.

The first part of understanding the theory is to accept a model of the earth that says that every place you can travel by foot is either a ridge, a valley or a place in between.

Hold on, you say, the earth is filled with features that are not ridges or valleys, like rivers, peaks, mesas or moors. My claim is these are all just special cases of ridges and valleys. A lake or creek is the locally lowest point in the valley you happen to be in. The peak ahead of you is the locally highest point on the ridge you happen to be following and the next pass the locally lowest point. A mesa is a wide flat ridge; a canyon, a narrow, deep valley, and so on. Makes sense?

The ridges and valleys of the earth come together in a repeating pattern called a drainage made up of two ridges and the valley between. Every drainage in turn connects to a larger drainage in a network that covers the planet. This network is fractal, it exists at every scale of observation from the tiniest crack in the mud at your feet to the grandest valley. Imagine the great plains of North America, while containing countless ridges and valleys, as itself an enormous valley, bounded on the west by the Rockies, on the east by the Appalachians, and drained by the Mississippi. Or picture the Pacific Ocean as flooding the incomprehensibly vast valley that lies between Asia and the Americas.

Aerial view of terrain showing fractal-like repeating patterns of interconnecting drainages at multiple scales
Photo by John Cobb on Unsplash

2. There are exactly three types of trails.

Returning to hiking and human scale, the second part of the theory says that traveling this system of ridges and valleys means moving within, or between, drainages. And doing this means following one of 3 kinds of trails:

  1. Trails that go up (or down) a valley,
  2. Trails that follow a ridge,
  3. Trails that traverse between valley and ridge trails, connecting either like or unlike types.

Here’s what these trails feel like:

Valley Trails

An array of 4 images depicting valley trails

Ridge Trails

An array of 4 images showing ridge trails

Traversing Trails

An array of 4 images showing traversing trails


OK, that’s it, that’s the theory. Here is how I use it to to orient myself.

Drainage Awareness

While hiking I maintain a drainage-aware mindset. This means being conscious of whether I expect my hike to keep me within the same drainage where I started or bring me to (and, if I’m looping, back from) a different drainage. At any point in my hike I can combine that expectation with the ridges and valleys I can currently see to anticipate when and how steeply I’ll be climbing or descending. This in turn enables me, even in unfamiliar terrain, to connect how I am feeling with the kind of time & effort I should be prepared for to complete my hike.

Trail Logic

Trail logic is about staying oriented where trails cross. It works like this:

  1. Because there are only 3 kinds of trails, the kind of trail I am currently on enables me to predict the kind of trail I am crossing.
  2. Valley to Valley crossings are rare while hiking because most valley hikes are in narrow valleys with only a single trail at the bottom. This is because a)broad valleys are usually developed, filled with people and not generally where you go hiking and b)even in undeveloped broad valleys trails tend to follow the single most direct route that stays closest to water.
  3. Traversing to Traversing crossings are also rare because terrestrial animals hate wasting energy so when going from a ridge to a ridge or from a ridge to a valley they will always create a trail along the single route that is simultaneously the most direct and least difficult. You may encounter traversing trails running parallel to each other at different elevation contours within a drainage, but you’ll almost never find them crossing.
  4. The most common kind of crossing is between a traverse and a valley or ridge trail. In pre-GPS trail running days, this insight was critical to being confident about my decisions at trail intersections. If I was on a ridge and knew I wanted to descend to the adjacent valley or get on the parallel ridge, then most likely, I wanted the next trail I encountered. Alternatively, if I was moving up a valley and knew I wanted to reach its head, I should keep to my current trail at every crossing. Today, even though GPS has greatly reduced the chance I’ll choose badly at a crossing, I still feel a boost of confidence and well being when I can connect drainage awareness and trail logic with the moving arrow on my phone screen.
  5. Passes are where you get lost. An easy way to visualize this critical piece of trail logic is to place your hand on a table, spread your fingers slightly while pushing down with the tips of your fingers and raising your knuckles. Imagine the shape that is formed as a piece of terrestrial topography where your fingers are parallel ridges running perpendicular to the ridge of your knuckles. Now start at the tip of your middle finger and imagine a hike that goes up the valley with your first finger and then returns down the valley with your ring finger back to the start. Notice that just after you reach the intersection with the knuckle ridge and begin descending — exhausted from the climb, carelessly elated to be going downhill and under heavy tree cover — it would be easy to walk past the head of the intended valley without noticing and instead enter the drainage between your ring and pinkie fingers. Forget to check your GPS and you will have a frustrating slog back up hill when you do realize your mistake.
Illustration showing how it is easy to get lost crossing a pass


Here are a few useful observations I wrap into my theory even though they don’t follow directly from the two principles.

Water is the locally lowest place.

Obvious to say, of course, but often helpful to remember in those moments when your GPS isn’t making sense with what you are seeing around you. If you want the fastest way down, follow the water; if you want the most direct way up, go against the water.

Bushwhacking is never a good idea.

This is so for two reasons. The first is simply that traveling through undergrowth is slow, unpleasant work. The second is that if the route you intend to bushwhack was actually a better way to get somewhere, then it would already be a trail. In other words, there is a reason, some kind of obstacle, that you can’t see that makes that route a bad way to go.

Animal trails go sensible places.

Non-human animals don’t like to get lost any more than human ones do. So if you are dead set on going somewhere your current trail doesn’t appear to be taking you, rather than bushwhack, find an animal trail. There are two caveats though. The first is that depending on the animal, travel may not be comfortable. In other words, it will be easy to walk an elephant trail, but following a deer trail will require some crawling on hands and knees. The other thing to consider is that some animal trails lead to animal sleeping places.


I can’t promise that Tim’s Theory of Trails will give you with the same feeling of having an orientation superpower that it does for me, but I can tell you that nearly every time I explain my theory to a new person the same thing happens. At first the person is nonplussed or amused and I get dismissed or maybe teased for claiming to have some grand insight about the simple act of hiking. Then, some time later, I’ll run into the person and they will say to me “hey, so you know, I was hiking the other day, and I thought about what you said about trails, and well, now I actually kind of see what you are talking about.”

Happy hiking.



Tim Sheiner

System thinker, story teller, designer, husband, father of 3, San Franciscan, Bernal Heights neighbor