Contours
Contour lines are the faint red-brown lines drawn on a map
connecting points of equal elevation above sea level, meaning if
you physically followed a contour line, the elevation (height of the
land) would remain the same.
Contour lines show elevation and the shape of the terrain. They're
useful because they illustrate the shape of the land surface on the
map. In other words, contour lines show the topography of the
land.
Understanding contours is a skill that will allow you to look at a
map and picture the hill, with depressions for streams, hills and
thin mountain ridges, etc
Contours
Contour lines are pictorial, meaning they do not exist on the ground.
Contour lines are critical to understanding the elevation profile of your terrain or a
particular land formation. This information can be helpful when selecting a hiking route.
In addition to backpacking and hiking, countless other professions use them - land
surveyors, architects foresters, engineers, miners, geologists, hunters and more.
A map with contour lines on it is called a Topographic Map.
Topography is the study of the geographical features of a landscape.
Contours
Topographic maps use a combination of colors, shading and contour lines to represent
changes in elevation and terrain shape. Specifically, a topographic map represents the
three-dimensional landscape of the Earth within the two-dimensional space of a map.
When checking quickly a topographic map you can immediately know if a landscape is
mountainous or flat.
If each line represents an equal point of elevation, then any change in elevation would
lead to inconsistent line spacing. For example, several contour lines spaced close
together would indicate steep terrain, while lines spaced far apart would indicate a
gentler slope.
Shallow slope (the contours are spaced apart)
Steep slope (the contours are close together)
There are 3 kinds of contour lines you’ll see on a map: intermediate, index, and
supplementary.
Index lines are the thickest contour lines and are usually labeled with a number at one
point along the line. This tells you the elevation above sea level.
Intermediate lines are the thinner, more common, lines between the index lines. They
usually don't have a number label. Typically one index line occurs for every five
intermediate lines.
Supplementary lines appear as dotted lines, indicating flatter terrain.