Maryland Outdoor Club
Everyday navigation
People navigate in the everyday world by figuring out where they are in relation to identifiable objects like:
Man-made features (roads, buildings)
Prominent landmarks (mountains, rivers)
Unique objects (the Statue of Liberty, the Brooklyn Bridge)
Compass directions (north, south)

People navigate using these objects all the time. Consider the following directions:

"Meet me at the corner of Elm and Main Street."
"Go south, then look for the baseball stadium on your right."
"Take I-75 toward the lake until you pass the big warehouse."

Wilderness Navigation
The difference between everyday navigation and wilderness navigation is that instead of using objects like buildings, intersections and streets to get from place to place, backpackers tend to use natural features and landmarks.

The tools of the trade

Maps - these provide you with a bird's-eye view of the prominent features in a given area. Knowing how these features relate spatially to one another can help you:
  • Figure out where you are on your map simply by looking at the world around you.
  • Figure out where your final destination is in relation to you, even if you can't see it (assuming you know your location on your map).
Map Basics
Backpackers typically have 2 options when it comes to choosing maps for their backpacking trips:
Planimetric maps - These describe the earth as if it were a flat surface. They provide basic information about distances, directions and the locations of prominent features (natural and man-made) in the map area. But they do not provide elevation information -- information about the shape/ height of natural features or the character of the terrain.
Topographic maps - These provide information about the physical contours of the land - things like elevation gains and losses, the steepness of hills, the deepness of valleys and the location and shape of natural features. Many also include information about prominent man-made features like trails, roads and bridges.
Both types of maps can be used for wilderness navigation. However, because they lack topographic detail, planimetric maps are typically used only on very short backpacking trips that follow well-established and well-defined trail systems. Remember -- a planimetric map can tell you where point A and point B are in relation to one another. But only a topographic map can also tell you what the terrain is like between the two so you can plan the best hiking route to get from one to the other.

How do topographic maps describe the terrain?

Topo maps describe the physical shape of the land using contour lines. These lines describe three-dimensional features by outlining them at specific elevation intervals (every 10, 20 or 50 feet, for example, depending upon the map being used).

The vertical difference between any two adjacent contour lines is always the same throughout a given map. This distance, called the contour interval, is identified at the bottom of each map.

Every fifth contour line is called an index contour line. Index contour lines have numeric elevations (usually measured in feet above sea level) printed on them that show how high all points along that line are.

Using the numeric information from the index contours and the interval information from the bottom of the map, you can figure out:

  • How high your current position is (assuming you know where you are on your map)
  • How high any other specific point on the map is
  • How steep the terrain is between where you are and where you want to go
The steepness of a given area on a topographic map is determined by how close together the contour lines are in that area. The closer the lines are together, the steeper the terrain will be.

So how do I choose the right topographic map?
To pick the right topo map for an upcoming backpacking trip, you need to consider 2 variables:
The scale of the map
The informational content of the map

Scale
The scale of a map basically describes how much the features on the map have been shrunk down. Map scales are typically described as ratios. A scale of 1:24,000, for example, means that one unit of distance (an inch, a foot, a meter, etc.) on the map equals 24,000 of those same units in real life.

To navigate successfully, you need enough detail on your map to see land features, terrain contours and landmarks clearly. In other words, a map of the United States won't help you find a campsite in your local state park. But you also want a map that covers enough ground that you don't have to carry 20 different maps just to cover your route. The key is to find a map scale that satisfies both needs.
Small-scale maps (with scales smaller than 1:62,500) cover a lot of land area, but they provide less detail as a result. They provide a good overview of a large area (perfect for trip planning), but tend to be a poor choice for specific trip navigation (not enough detail).
Large-scale maps (with scales of 1:62,500 or larger) focus on more specific areas and provide more detail. They are better suited to most backpacker's navigation needs. NOTE: The terms "small-scale" and "large-scale" are often confusing to beginners, since ratios get smaller as their denominators get larger. Keep in mind that 1:24,000 is a larger scale than 1:250,000, since the fraction 1/24,000 is larger than 1/250,000.

Informational Content
The non-topographic information that a map provides can be as crucial to navigation as the topographic information, especially for beginning backpackers. This additional information includes things like:
The location of hiking trails and campsites
The proximity of nearby attractions and recreational opportunities
The paths of access roads in the area
Wilderness area boundaries

Different maps provide different levels of this information. Here's a look at your basic map options, and the kinds of information they typically include:

USGS quadrangles

The major supplier of topographic maps in the United States is the United States Geological Survey (USGS). USGS maps cover rectangular areas of land called quadrangles. The borders of these maps are determined by latitude lines, longitude lines and the smaller divisions between them (minutes). Every square mile of the United States is covered by USGS maps, and each map lines up flush with the others around it.


Positives - USGS quads are easy to find, easy to use and easy to fit together when your trail crosses over onto an adjacent map (the borders match exactly, and the titles of adjacent maps are printed on the borders of each map).
Negatives - USGS quads tend to provide limited trail information. They also tend to be somewhat older than other map options, which can cause problems if features like roads, bridges, trails and shorelines have changed since the map was printed.

Privately produced quadrangles

Many private map companies offer topographic maps that cover the same rectangular sections of land as USGS maps, but with more up-to-date details about trail systems and recreation opportunities.

Positives - These maps often have more relevant backpacking information than USGS quads, and they tend to be updated/revised more frequently to show changes. Negatives - Privately produced quads are often more expensive than USGS quads, and they are usually available for popular backpacking areas only.

Wilderness area maps

Many government-owned wilderness areas (national parks, national forests, state parks, recreational areas and so on) produce their own maps to cover the land inside their boundaries. Some of these maps are planimetric only. But many are topographic.

Positives - These maps cover entire wilderness areas on a single map, usually with information about roads, attractions and trails. Many are updated frequently to reflect changes in trails and facilities within park boundaries. Negatives - Wilderness area maps often cover such large areas that they don't provide enough topographic detail for backpackers. This is especially true for the larger wilderness areas.

Trail-specific maps

Some private companies produce topographic maps that are shaped to cover a specific backpacking trail or trail system. These maps typically offer the same topographic information as other maps. But they cover irregularly-shaped sections of land so that a specific trail or route-filled area is covered on a single sheet of paper.

Positives - These maps save money and hassle by providing all the topographic information you need for an entire route on a single sheet of paper. Negatives - Trail-specific maps are only available for a limited number of popular trails.

Topographic CD-ROMS

Many popular backpacking areas are now covered by topographic CD-ROMS. These computer software programs typically cover wide areas of wilderness, yet provide topo information in a variety of scales.

Positives - These programs let backpackers do amazing things that aren't possible with printed maps, like:
  • Custom map printing -- Some programs let you build and print maps that cover the specific areas you're interested in, no matter what scale you're looking for.
  • Search-capability -- Looking for a specific lake or trail head? Some programs can take you right to it.
  • Topographic imaging -- Having a hard time visualizing what a set of topographic lines looks like in real-life? Some programs can convert them and show you how hard your hiking trail will be!
  • Route-specific information -- If you trace your route on a computer map in some programs, the program will tell you how long, how high and how steep the route is.
Negatives - You need a computer with CD-ROM technology to use these software packages. CD-ROMs cost more up front than regular paper maps (though over the long run, they can be far less costly). Map CD-ROM are currently only available for limited wilderness areas.