Winter Travel Series #1: Learning About Terrain

This is the first post in a 5-part series covering our favorite CalTopo layers and tools for planning winter backcountry travel. Each post will dive into a different stage in the process, from learning about the terrain to actually heading out into the backcountry with the mobile app. We will largely be focusing on the web app but many of the layers and tools are also available in the mobile app. Now let it snow!

Learning about Terrain

Learning about terrain can be a daunting undertaking, particularly if the area is new to you. Map layers like topographic maps, aerial imagery and slope angle shading can provide great insight into the natural features of an area from the comfort of your computer or mobile device. Let’s dig more into each of these layers and how you can use them to plan winter backcountry travel.

Compare Topo Maps to Get a Lay of the Land

A great place to start is with a topographic map, such as MapBuilder Topo. 

Topographic maps like MapBuilder Topo can tell you a lot about an area.

This topo map is CalTopo’s signature base layer and it incorporates data from a variety of sources including trail and road data from OpenStreetMap, peak names from Peakbagger and relief shading based on USGS elevation data sets.

Contour lines and relief shading can reveal possible ascents, descents and travel routes.

Topo maps are helpful for visualizing the lay of the land. Using the contour lines, you can identify broad ridges or low angle slopes that may be good ascent routes. If you’re planning to ride or ski, you can also spot potentially good fall line descents. Relief shading makes these features stand out even more, helping you to identify them faster.

Topo maps also provide information on important features and points of interest, such as trailheads, logging roads, summer trails, and bodies of water. There is no one map that is the definitive source of truth about an area; rather, different maps display data from different data sources. Switching between topo maps and comparing the information present on each can provide more information about an area than just looking at one topo map alone.

For example, the image below shows the MapBuilder Topo and Forest Service layers (which displays official Forest Service data) in the same area. Drag the slider from side to side to compare the information present on each layer. How do the names of the peaks compare? Which layer shows trailhead locations? What features are present on one layer but absent on the other?

With CalTopo, you aren’t limited to just one topo map. You can easily switch between base layers or stack them on top of each other, allowing you to gather even more data about the area that you are interested in.

Visualize the Terrain with Aerial Imagery

While many topo maps include vegetation shading, diving into the aerial imagery for an area can really help you to learn more about what the terrain is actually like.

Finding the right tree density can be the difference between easier travel and a miserable bushwhack.

Even though much of the land itself is covered in (ideally) snow, aerial imagery, such as Global Imagery, can provide important insight about the underlying terrain for planning winter backcountry travel. Is a slope normally covered in rocks and talus or is it grassy? Where are the open meadows? Are the trees in an area densely packed or more spaced out? 

If you are in the continental United States, a particularly useful layer is NAIP. Like many of the layers on CalTopo, NAIP is configurable. Changing NAIP to false color IR causes healthy vegetation to appear bright red, making it pop even more. This can help you to identify areas where the trees are densely packed (potentially presenting a miserable bushwhack) and areas where the trees are more evenly distributed (which could mean easier travel or more enjoyable tree skiing and riding). 

If you are only viewing aerial imagery, adding the contour lines overlay or stacking relief shading in conjunction with the imagery can allow you to better visualize changes in elevation. You can also try stacking a topo map and adjusting the transparency to provide geographic context so you know exactly what peak or valley you are looking at. 

Two layers can be better than one. Stacking aerial imagery with a topo map allows you to view the actual terrain with geographic context.

Dig into Slope Steepness with Slope Angle Shading

A popular year-round tool, slope angle shading is a visual overlay that uses a color scheme to identify slope steepness based on USGS elevation data sets, including high-resolution LIDAR data from the 3DEP program where available.

Each color corresponds to a different slope angle range. For example, red indicates slopes with 35-45 degree slope angle.

This overlay can provide great insight for planning winter backcountry travel: it can help you to identify gentle slopes that may be easier to ascend, manage avalanche danger, spot potential terrain traps, and more.

It’s important to note that slope angle shading can be an incredibly useful tool for increasing situational awareness but it is not the absolute truth. All slope angle shading has limitations, including errors in the source data as well as missing or creating terrain features based on the resolution of the underlying data. 

Slope angle shading is most useful when combined with observations of the physical terrain, such as measuring slope angle with an inclinometer. We strongly encourage you to seek out professional training to learn more about traveling through avalanche terrain. Our partners at the American Avalanche Association and Avalanche Canada have some great resources to get you started or continue your education- make sure to check them out!

Try Different Layers and Combinations

As you start to explore a new area and plan your day, don’t be afraid to switch between different layers or try out new combinations. You may find that a topo map paired with slope angle shading to distinguish between gentle and steep slopes is really helpful for planning your initial route. Switching to aerial imagery stacked with shaded relief may provide insight into whether the route you planned is actually feasible given the terrain. CalTopo provides a wide array of base layers and overlays to choose from, allowing you to dive deep into the terrain before you step out the door.

Switching between different layers can reveal more about an area that just sticking with one layer.

Now it’s your turn! Are there any layers or tools we missed that you find particularly useful for learning about terrain in the winter? Question or comments? Leave them below.

Next week we’ll cover creating a map and planning your route. Until then, happy mapping!