Even in the age of GPS devices and cell phones that can pinpoint your location within feet, nothing is as simple, useful, and trustworthy as a good map. But maps haven’t been immune to the same technological advances that brought us our fancy electronics.

Rather than visiting a store to search through set USGS Quads, atlases, or pre-set maps, today’s adventurers have the ability to customize their own to their exact specifications. The type of map, its details, the trails and points displayed on it, and its area can all be tweaked and adjusted, so that when you head outside, you have the exact combination you need. To make your own, the data is out there, if you can figure out how to put it together.

What are “layers?”

Layers are map sections that can be examined on their own or, through a program, overlaid onto another map to compare and contrast details. For example, when you visit Google Maps, you can choose between street maps, satellite images, and even terrain. By adding traffic conditions or bicycle routes, you’re overlaying one layer on top of another to view even more data.

There are almost too many types of map layers to count, but these are some of the most commonly used ones:

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Google Maps

With 1 billion monthly users, Google Maps is probably the most well-known mapping site. It offers three different layers, including Street, Terrain, and Satellite, and has a few additional ones that can be turned on and off, including bike paths and traffic.

If you are trying to get to or return from the trailhead, Google Maps is definitely the best choice for avoiding the traffic and then finding some food after. However, while it adds some vague trails, other stronger options can help you find your way in the outdoors.

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USGS Topo

Using U.S. Geologic Survey data, the basis for decades’ worth of maps, the USGS topographical map is the most common layer for reading and navigating the outdoors. At a basic level, USGS maps show you roads, dirt roads, and trails, as well as clearings and many other manmade structures. Caltopo.com contains the full USGS map layer, which covers the entire country.

If you plan on traveling off the trail, a USGS or similar topographical map is a must-have for navigation. As you’re outdoors, use the elevation and land features to keep track of your position.

To add to the information you get from the USGS’ basic topo lines, layer in slope shading. Slope shading highlights based on the slope angle, which then shows where hills and mountains get more or less steep and helps you identify cliffs for rock and ice climbing. For backcountry skiers and snowboarders, this feature assists with planning approaches and descents while minimizing avalanche risk.

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Satellite and Aerial Imagery

Satellite images show texture and visual details that most map layers can’t capture. If you plan to check out specific terrain features or vegetation cover, this type assists with examining these facets more closely. Both Google and Bing Maps have satellite imagery, but the latter uses images from late winter or early spring. This combination allows you to see through the canopy and get more detail in the forests than you would from summertime-only images. As a result, you can look at the area around the cliff to identify trails that might not be mapped otherwise—a benefit to rock climbers looking for approach and descent trails.

Bing maps also have bird’s-eye view aerial imagery, and Google Maps offers a 3D function. Both options create more up-close imagery and provide a perspective different from straight satellite views. In the outdoors, bird’s-eye view can be useful for inspecting cliff faces for climbing routes or even looking at new areas in more detail before you make the trip out.

As another asset, Caltopo lets you layer topo maps over a satellite image to see contour lines on top. Doing so might help you make better sense of an otherwise-2D image—for instance, before finding climbing slides in places like the Adirondacks. First, the satellite images allow you to see the slide itself and pick out your route, and then, the topo map adds terrain information and even trails before and after.

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Map Builder Topo

Map Builder Topo is a Caltopo layer that uses USGS contours as a base, but then adds in a huge number of up-to-date trails and other waypoints. This layer is helpful for figuring out the best trails to get to where you want to go.

Caltopo allows you to add lines and waypoints, which can be measured for distance and elevation gain. If you are planning a hike, trail run, or even a paddle and want to know the route statistics, this tool gives you a good start. One fault, however, is it makes no distinction between hiking and biking trails. Thus, if you use it to go exploring with your bike, you might find yourself on gnarly terrain or trespassing on hiking-only trails.

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OSM Bike

The Open Cycle layer uses many of Map Builder’s trails, but softens the contours. Here, color-coded brown and blue indicate hiking and biking trails, respectively. As a result, this tool is essential for developing bike touring and bikepacking routes.

In addition to trails, it also highlights popular roads for cycling, as well as bike paths and lanes. When you want to get off the bike, it indicates important landmarks, such as campgrounds, hotels, hospitals, bike shops, coffee shops, and breweries.

Keep in mind that Open Cycle Map is open source. As such, the cycling community constantly updates it with the latest trail information.

Almost all of the map layers above can be accessed on Caltopo.com, one of the many free online mapping sites. So, before you plan to visit an area, take the time to review each map layer’s specific details. In doing so, you might even find something worth traveling to on its own.

Make Your Map

After you’ve decided on the layers forming your map’s core, you can customize it even further. Caltopo.com allows you to add waypoints, tracks, and more facets, just like you would with GPS software like Garmin BaseCamp.

Then, once you have your map set up with all the data you might want on your hike, paddle, or climb, print it out yourself. Use Rite in the Rain or National Geographic waterproof printer paper for a durable, outdoor-ready map, and then, hit the trails!