Topography accurately represents the contours of a surface.
Topographic surface maps, also called topo or contour maps, provide a point of reference, accurately depicting features of a surface through contour lines, colors and symbols. Typically, topographic surface maps refer to the accurate representations of hills, valleys, rivers, lakes, streams, trails and wooded areas as well as man-made features, including dams and roads; however, topography also refers to planetary features, such as the moon's craters or the human body. Today's topographic maps utilize advanced sensing equipment to interpret aerial photographs of a region, creating extremely accurate topographic surface maps.
Contour Lines
The imaginary line on a topographic map, called a contour line, represents features the earth's surface. Every part along the contour line is at the same elevation (altitude) above some datum (reference plane); therefore, contour lines never cross. For most topographic maps, the datum is sea level.
Contour lines represent the elevation of the terrain. Lines close together represent steep terrain, while widely spaced or absent contour lines means flatter ground. The elevation difference between contours, called the contour level, shows the general shape of the terrain. A relatively flat expanse may have a contour interval up to 10 feet. Mountainous areas may require contour intervals of 100 feet or more. This information is especially useful when traversing unfamiliar territory.
Colors
Topographic maps not only reveal the contours of the earth's surface, but significant streams, forests, buildings and other points of interest. USGA topographic maps use colors to identify the different features. Brown represents surface contours (elevation). Black symbols represent man-made features, such as roads, buildings and boundaries. The color blue indicates bodies of water, such as lakes, rivers and streams. The color green indicates a region with substantial vegetation, where white represents sparsely vegetated areas. Red indicates the principal highways and boundaries between the public land areas. White with blue indicates permanent snowfields and glaciers. Purple represents the features added to the map since the original survey.
Symbols
A topographical surface map includes symbols representing features, such as streets, buildings, vegetation and rivers. The symbols are continually being refined to improve readability of the map or reduce the cost of production.
Topographic Profile
A topographic profile is a cross section view of an area. If you slice the Earth in half, and view the surface area from the side (profile), you have created a topographical profile. This form of surface map not only helps you understand topographic maps, geologists find it useful in analyzing various geological problems, such as volcanoes.
3-D Surface Topography
Unlike traditional 2-D topography surface maps, 3-D maps realistically represent the natural characteristics of a surface, such as whether deep valleys derive from pits or troughs. 3-D surface topography also provides additional parameters, such as oil volume, debris volume and contact areas---allowing engineers to analyze the functional properties of surfaces.
Tags: surface maps, topographic maps, features such, blue indicates, called contour, contour line
