![]() When the lines are close together the magnitude of the gradient is large: the variation is steep. The gradient of the function is always perpendicular to the contour lines. The contour interval of a contour map is the difference in elevation between successive contour lines. A contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes. In cartography, a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level. More generally, a contour line for a function of two variables is a curve connecting points where the function has the same particular value. It is a plane section of the three-dimensional graph of the function f ( x, y ) -plane. Line 1 starts with the contour interval, not the projection point.A two-dimensional contour graph of the three-dimensional surface in the above picture.Ī contour line (also isoline, isopleth, or isarithm) of a function of two variables is a curve along which the function has a constant value, so that the curve joins points of equal value. ![]() Slope Worksheet - Use the information from the example above and complete the slope worksheet. The run is 1000 feet and the rise in elevation is 120 feet. Step 4. Use the slope percent equation and solve. Set up the cancellation table so all units will cancel, except the desired unit, feet. Step 2. Use the appropriate conversion factor to convert the horizontal map distance to horizontal ground distance. The horizontal map distance measures 0.5 inches. Step 1. Measure the horizontal map distance between points A and B to get the vertical ground distance. The horizontal distance between points A and B can be measured with a scaled ruler and used to determine the slope percent.Įxample 4 - What is the slope percent in Exercise 2 above?įor this computation, the rise, or vertical ground distance, and run, or horizontal ground distance, are needed. Notice the tick marks pointing toward lower elevation. The figure above illustrates a depression and its representation using contour lines. (b) Notice how a mountain saddle, a ridge, a stream, a steep area, and a flat area are shown with contour lines. The figure above illustrates various topographic features. Contour lines that are very close together indicate a steep slope. Widely separated contour lines indicate a gentle slope. ![]() The peak is normally considered to be located at half the interval distance. Note: The intervals are increasing, therefore, the contours indicate a hill. From the contour map, a profile can be drawn of the terrain.Įxample 2 - Draw a profile showing the elevations of the contours. ![]() The even spacing indicates the hill has a uniform slope. The contour lines in this figure are equally spaced. Pick two contour lines that are next to each other and find the difference in associated numbers. Sharp contour points indicate pointed ridges.Įxample 1 - In the graphic below, what is the vertical distance between the contour lines? Contour lines tend to enclose the smallest areas on ridge tops, which are often narrow or very limited in spatial extent. A rounded contour indicates a flatter or wider drainage or spur. They then cross the stream and turn back along the opposite bank of the stream forming a "v". As a contour approaches a stream, canyon, or drainage area, the contour lines turn upstream. If the numbers associated with the contour lines are decreasing, there is a decrease in elevation. If the numbers associated with specific contour lines are increasing, the elevation of the terrain is also increasing. Index contours are bold or thicker lines that appear at every fifth contour line. ![]() A contour interval is the vertical distance or difference in elevation between contour lines. A contour line is a line drawn on a topographic map to indicate ground elevation or depression. ![]()
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