A Gentle Introduction to CalTopo

Today I was talking to one of the fine folks over at the Rustic Red Hostel over on Facebook when it came to my attention that he was unaware of CalTopo. This individual in question is an avid off-trail explorer in The Red River Gorge. It absolutely blew my mind that he had never heard of what is probably one of the greatest mapping utilities ever made for the backcountry explorer! So, today we are going to right this atrocity and take a look at just what CalTopo is and how we can use it.

CalTopo Screencast

To help you follow along with this introduction, I’ve also recorded a screencast. I think some of the stuff introduced here are much easier to follow when you actually see them being done. It’s also worth noting that the screencast has a couple bits of “bonus” information in it that I didn’t include in this post.

What is CalTopo?

So the first question we need to answer is: “What on Earth is CalTopo“? Well, it’s a topographic mapping utility. At the simplest level, CalTopo is an online application that lets you view and print topographic maps of the United States. Dive a little deeper, however, and you will find out that CalTopo has A LOT more to offer than just that.

You can stack layers, add markers, measure distances and so much more with this handy utility. So, let’s quit wasting time and dive right into it!

To get started, simply head on over to CalTopo.com. You will be greeted with a screen similar to this one:

CalTopo initial view
CalTopo initial view

For the purposes of demonstrating this app, I’m going to navigate to a place that I’m familiar with: The Red River Gorge. To do this, simply head on up to the search bar and search for Red River Gorge.

The CalTopo search bar.
The CalTopo search bar.

Now simply hit the GO button and the map view will update to be centered on The Red River Gorge, Kentucky.

At this point you should already be able to see how having this topo view would come in handy, but it gets even better than this! Let’s next take a look at the map layers.

Map Layers

The map displayed within CalTopo is built by stacking layers on top of each other. If you’re familiar with layers in an image editing program, like Photoshop, the concept here is similar. If not, the concept should be more familiar once we complete this section.

The Default Layer

The default layer is the one you see in the screenshot above. It’s built by taking all the individual maps provided by the United States Geological survey and stitching them together into one giant, continuous map.

This is all well and good, but it has a few problems, such as:

  • These maps were produced and updated at during periods. This can lead to a level of inconsistency between areas on the map.
  • Different sections of the map have a different look and feel. This is, in my opinion, a jarring experience and can make things a bit harder to read.
  • The map data from the USGS was obtained by scanning copies of physical maps. This means that the resolution on these maps isn’t the greatest.

It’s for these reasons that I don’t prefer the default map view. Luckily, we can change to some other preset by clicking on the various preset layers in the side pane:

Caltopo Preset Layers Panel
Caltopo Preset Layers Panel

The MapBuilder Topo Layer

The first preset layer we’ll take a look at is the MapBuilder Topo Layer. This layer is an alternative to the default layer we discussed above. This preset also has the advantage of sometimes including trails that aren’t listed on other official maps.

 CalTopo Map builder Topo Layer
CalTopo Map builder Topo Layer

The Forest Service Layer

I’m going to skip over the 7.5′ Topo Map preset since it’s basically just the default layer with some relief shading (which is a fancy way of saying it makes the terrain look a bit more 3-D).

With that being said, I want to take a look at the Forest Service preset, which is my favorite one to use, when applicable.

You see, the United States Forest Service has actually made their own series of maps for lands that fall within forest service boundaries. They are, in my opinion, some of the best maps available. If you’re going to be in an area covered by the USFS, then I suggest using this layer. It’s also worth mentioning that, for the areas that fall outside the boundaries of the USFS, CalTopo just falls back to the default maps from the USGS.

Okay, enough blabbing, let’s see an example of this layer already!

CalTopo Forest Service Layer
CalTopo Forest Service Layer

The Slope Angle Shading Layer

The last preset layer I want to discuss here is the Slope Angle Shading Layer. This one is a pretty unique feature, and it’s super helpful for planning routes.

When you select this layer, you will be greeted with an almost heat-map-like view.

CalTopo Slope Angle Shading Layer
CalTopo Slope Angle Shading Layer

We can use this shading to judge how steep a given slope is. If you look up in the upper-right hand corner, you will see an explanation of what these colors mean:

Caltopo Slope Angle Shading Key
CalTopo Slope Angle Shading Key

So, as you can see, yellow indicates that a slope has an angle of roughly 27-29 degrees, whereas black indicates a slope of 60+ degrees. To get a better idea of how this shading translates to actual terrain, let’s consider an example: Auxier Ridge in Red River Gorge.

Example slope angle shading on Auxier Ridge, Red River Gorge, Kentucky.
Example slope angle shading on Auxier Ridge, Red River Gorge, Kentucky.

As you can see, the area I’ve pointed to has a slope shading to red and blue. This means that, for any given point along this section, the angle of the slope will be somewhere between 35-59 degrees. What does that actually look like, you ask? Well, let’s take a look at a shot I’ve taken of this particular spot:

Goind Down

As you can see, that shading corresponds to a rather steep slope indeed!

Just as a more extreme example, here’s what the shading looks like around Mt. Denali:

Example slope angle shading for Mt. Denali
Example slope angle shading for Mt. Denali

Stacking Layers

Let’s say I want to have the slope angle shading we just discussed above, but I instead want it overlayed on the forest service map. How could I go about this? Well, the answer is by stacking layers. Select the forest service map layer, and click the box that says USGS 7.5′ in the upper right-hand corner. Doing so will bring up a menu.