These lines are drawn at all one elevation, but they differ from the previous two types of lines in that their spacing or change in elevation that they represent is different. Supplemental Contours Supplementary contours are drawn as dashed lines or lines of dots. They are used to represent a smaller change in elevation than the intermediate contour. SUPPLEMENTAL CONTOURS A supplementary contour is used when the elevation change is minimal, like in flat floodplains. This technique is called feathering (see Fig. Intermediate Contours Intermediate contours are so closely spaced as to nearly unite or merge into a single line, it is standard practice for readability not to portray the lines for short distances. Intermediate Contours These lines are not usually labelled except where the terrain is relatively flat and elevations are not readily obvious They are numbered on the upper side of each line, which indicates at first sight uphill and downhill directions, placing the figures in a row above one another.ĬONTOURS 2.INTERMEDIATE CONTOURS The four lighter weight contours found between the index contours. The index contour is broken along portions of the line and the contour number indicated accordingly. They are usually drawn every fifth contour and carry the contour number or the elevation designation. These heavier lines which are normally twice the gauge of the standard contours. Approximate Contours Intermediate Contour LinesĬONTOURS 1.INDEX CONTOURS Index contour is shown by a heavier line at regular intervals on a topographic map.
Contour line – a line on the map representing a contour. Contour line – a line on the."- Presentation transcript:ĭefinitions: Contour – an imaginary line of constant elevation on the ground surface. Definitions: Contour – an imaginary line of constant elevation on the ground surface. Line 1 starts with the contour interval, not the projection point.Presentation on theme: "CONTOURS Engr. 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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