Such lines are called index contour lines. In most topographic maps every 5th contour line is drawn in bold print or wider than other contours.
Usually the contour interval is noted on the map legend. The elevation difference between two adjacent contour lines is called the contour interval (CI). In the above topo map, the summit of the hill is marked with a 192m spot elevation.Ĭontour Interval - Types of Contour Lines: Index, Intermediate, Supplementary Spot elevations are less accurate and precise than benchmarks, however they are more accurate than contour elevations. In USGS topo maps bechmarks are indicatd with letters BM and black cross.Ī spot elevation is usually indicated on topo maps by a cross, a dot or an X. Benchmarks are used as reference points in surveying. On the ground a benchmark is usually marked with an engraved brass plate indicating the height above mean sea level of that location. Benchmarks are established using ground based surveying. summit, ridge line, right of way, lake surface, depression, etc.) on topo maps may be indicated by benchmarks or spot elevations. Specific elevation of certain points (e.g. Evenly spaced contours represent a uniform slope. irregular circles) are used to represent hills, mountain summits, knolls, horns, etc.Ĭontour lines with wider spacing represent gentle slope, while the closer spaced contours indicate steeper terrain.
#Contour map series
In this image, a hill (three-dimensional feature) is represented by a two-dimensional contour map.Ī series of concentric closed contours (i.e. You can find more examples of isolines in this website. Isohyet connects points that have an equal amount of precipitation during a certain period. Examples include: an isobath connects points of equal depth under water an isobar connects points that have equal amount of pressure an isotherm connects points of equal temperature an
#Contour map how to
You will learn how to read and interpret topographic maps through examples.Ĭontour lines, isolines, or isograms are used widely in different fields such as meteorology, geology, oceanography, and other sciences to represent lines with equal Representation of landforms and terrain features by contour lines is covered in depth in the next two sections. Looking at a flat two-dimensional map with contour lines you can get a sense of the shape of the three-dimensional land surface ( topography) such as mountains and vallyes. Never cross each other (with the exception of representing overhanging cliffs or caves). Each contour line corresponds to a specific elevation, therefore contour lines UTM, latitude - longitude, Universal Polar Stereographic (UPS), or Military Grid Reference System (MGRS) coordinate systems).Ĭontour lines in topographic maps ( topographic contours) are imaginery lines that connect points of equal elevation above a reference level (usually mean sea level). Toponomy or feature and place names are added to provide textual information about features.Īpart from the location map with symbols and contours, topo maps may also include map scale, legend, declination diagram, datum, projection, UTM zone, north arrow, production info, date of revision, and grid lines (e.g. Natural features may include water (rivers, streams, lakes, wetlands and swamps, rapids), relief (mountains, valleys, canyons, and other landforms.), vegetation (forested areas, cleared areas, orchards. For example cultural features can be roads, trails, buildings, boundaries, railways, power transmission lines, pipeline, campgrounds, mines, dams, recreation areas.
Symbols and colors are used in topographic maps to identify cultural and natural features. Topographic maps are a form of contour maps and the terms are used interchangeably. Of such maps is the representation of the three-dimensional terrain or relief of the surface of the earth by the use of contour lines. Topographic maps provide a detailed represention of the natural and man-made features of the earth's surface. Home > Education > Topographic Maps - Contour Lines Topographic Maps (Topo Maps) and Contour Lines
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