A Gentle Introduction to CalTopo

Today I was talking to a friend of mine 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 of 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

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 up to the search bar and search for Red River Gorge.

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 during periods of time. 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

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

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

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

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

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.

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:

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

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.

This menu allows you to overlay all sorts of things onto your map. The example I gave above was adding the slope angle shading. To do this, simply check the Slope Angle Shading box and it will be overlayed onto the map.

Let’s say I want to instead get an idea of how much sun exposure a given area on the map receives. I can achieve this by checking the Sun Exposure box. NOTE: It might take a bit for this option to render on the map since it has to calculate the sun exposure for every visible location on the map.

Just The Tip of the Iceberg

When it comes to all the layer options available in CalTopo, this is just the tip of the iceberg! There is so much more you can do by stacking layers on top of each other. My best suggestion would be to just play around with it, since going into more detail than this would be far beyond the scope of this introduction!

Adding Objects to the Map

If you thought the layers were all there is to CalTopo, then you’re sorely mistaken! We can also add a myriad of objects to the map. An object can be anything from a marker on the map, to a highlighted trail, or even shapes or bearing lines. Objects are added by clicking the + Add New Object link on the left-hand side of the webpage. It will bring up a list of options for objects you can add.

Let’s take a look at some practical examples!

Adding a Marker

The simplest object we can add to our map is a marker. As the name implies, it simply marks a spot on the map.

You add a marker by selecting Add Marker from the + Add New Object menu. Doing so will place a marker in the center of the map, and display a window in the bottom right-hand corner where can configure the marker.

Looking at the marker settings window, you can see that I can give the marker a name, enter comments about the marker, set the GPS coordinates, and even change the style and color. NOTE: You don’t have to type in the GPS coordinates to move the marker. You can actually click and drag it with your mouse!

Let’s consider an example:

Assume I’m planning a trip to the top of Raven’s Rock. Like any responsible hiker, I intend to take some good, detailed maps with me on my trip. As such, I would like to place a marker on the summit of Raven’s Rock. I’d like the marker to be blue, use an open circle icon instead of the default one and I’d like it to be named ‘Raven’s Rock Summit.

All I have to do to achieve this is move the marker to the top of Raven’s Rock with my mouse, and change the relevant settings.

Once I click the OK button, the marker will be added to my map.

Adding a Line

Another simple object that we can add to a map is a line. We can add a line by selecting the Add Line option from the + Add New Object menu. Once you do this, simply left-click to select the start of the line, drag your mouse to where you want the line to end, and left-click again to set the end.

You’ll notice that after you select the endpoint, CalTopo will automatically start a new line from the end of the line you just drew. This allows you to continuously draw a line that could represent an intended path of travel. When you are done, you can set a label, comment, color, and line thickness down in the settings window and hit OK.

What we’ve covered about lines up until this point is cool all on its own, but there is one more really cool feature about the line tool in CalTopo: We can use it to automagically highlight a trail.

Let’s return to my previous Raven’s Rock example. Let’s now say I want to add a line that highlights the trail up to the summit of Raven’s. I could sit there and draw a bunch of lines on the map to highlight the trail, but I don’t have to. You’ll notice that when you select the add line option, all the trails become highlightable. If I hover my mouse over These trails, I can click them and have CalTopo do the hard work of drawing a line along the trail!

NOTE: I realize that the above explanation may not be super clear. If it’s at all ambiguous, just refer to the screencast!

Range Ring

Let’s say I want to see everything that falls within a 1-mile radius of the summit of Raven’s Rock.

I can do this by selecting the Add Range Ring option and setting it to be a 1-mile radius. This feature can be useful for numerous applications, such as planning search areas based on Lost Person Behavior during search and rescue callouts.

An example 1-mile radius range ring.

Unfortunately, you can’t currently move the range ring around with your mouse, so you’ll have to input the coordinates you want it centered on. Once doing so, however, we will have a 1-mile radius circle on our map.

Again, Just the Tip of the Iceberg

Once again, this is just the tip of the iceberg of what’s possible! You can add so much more to your maps than what we discuss here, including shapes and bearing lines. It’s far beyond the scope of this post to discuss everything you can do, so I’m going to again encourage you to play around!

Printing Your Maps

The last thing I’m going to discuss here is printing your maps. There are far more things you can do, such as exporting the maps to GPX or even importing GPX files into CalTopo, but I’ll save those for a later date if anyone’s interested!

Let’s say I’m happy with the map I’ve made for my trip up Raven’s Rock and I’m ready to print it out. Simply hit the print button in the top toolbar area.

Doing so will open up a utility to generate a PDF copy of your map. You’ll notice a resizable red square on top of your map. You resize this and position it over the area you want to be printed on the page. It’s also worth mentioning that you can still zoom in and out and move the map around.

This is all well and good, but what if, in addition to this large overview map, I’d like another page to be a detailed view of the summit area of Raven’s Rock? Do you have to do this whole process again? Luckily the answer is no!

Simply select the + Add Page option, which will give you another adjustable square.

As you can see, I now have another adjustable view. Each red square represents a single page within the PDF that will be generated. This means I can export a PDF that has as many pages as needed to cover the portions of the map I need.

When we’re done adding pages, all we have to do is click the Generate PDF button.

This will generate a PDF will all the pages you’ve set up, as well as an overview page, which you can then print and/or download.

That’s it for Now

Whew, that ended up being a long-winded introduction! Hopefully, you found this to be a useful and generally gentle introduction to CalTopo. If anything was unclear, try watching the screencast to see if that clears things up at all. If not, don’t hesitate to ask!

What Did I Miss?

Did I forget to cover something here you think I should’ve? Please don’t hesitate to let me know in the comments down below!

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