Civil Drafting Technology

Civil Drafting Technology Chapter 9 Contour Lines

Figure 9–1: Contour lines formed by lapping water at different levels in a reservoir. (Reproduced by permission of City of Portland Oregon)

Figure 9–2: Uniform gentle slope.

Figure 9–3: Uniform steep slope.

Figure 9–4: Concave slope.

Figure 9–5: Convex slope.

Figure 9–6: Contours merge to form a cliff.

Figure 9–7: (a) Contours form a “V” pointing upstream. (b) Contours form an “M” above stream junctions. The tops of the M point upstream. (c) Contours form a “U” around ridges. The bottom of the U points downhill.

Figure 9–8: (a) Dome-shaped hill. (b) Saddle. (c) Depression. (d) Overhang.

Figure 9–9: Types of contour lines.

Figure 9–10: Every fifth line is an index contour, and the contour interval determines the value of the index.

Figure 9–11: Contour map plotted using control point survey.

Figure 9–12: Interpolating contour lines.

Figure 9–13: When interpolating contour lines using the uniform slope theory, always space contours evenly as in part c of the figure.

Figure 9–14: Mathematical interpolation of contour lines allows you to calculate the distance between two points.

Figure 9–15: The map distance between two points can be used to determine the percent of slope. The slope is converted to a distance between a given elevation and a contour line.

Figure 9–16: (a) For a grid survey, land is divided into a checkerboard and labeled. (b) All grid intersections are labeled. (c) Connect the elevations with courved lines or splines. (d) Completed contour map of grid survey.

Table 9–1: Grid survey field notes for the map in Figure 9–16

Figure 9–17a: The theory of uniform slopes is used to calculate contours in a grid survey.

Figure 9–17b: After elevation values are located on the grid, points of the same value are connected to form contour lines.

Figure 9–18: Field notes of a radial survey contain azimuths and distances, property corners, and additional control points.

Figure 9–19: A property plat can be constructed from the radial survey field notes.

Figure 9–20: Contour line labeling should be on index contours, placed at regular intervals, and should not appear upside down.

Figure 9–21: The Carlson SurvCom program transfers data from a survey instrument to an office computer. (Courtesy Carlson Software)

Figure 9–22: Options in the Triangulate tab control how the triangulated mesh is represented in the drawing as well as the naming and placement of the external TIN file. (Courtesy Carlson Software)

Figure 9–23: The Contour tab is where all aspects of the generated contours are controlled, including the interval and smoothing. (Courtesy Carlson Software)

Figure 9–24: In the Labels tab, the user specifies the details of the creation of contour labels. (Courtesy Carlson Software)

Figure 9–25: The Selection tab is where the user specifies what type(s) of data is to be used to generate the surface. (Courtesy Carlson Software)

Figure 9–26: An example of a contour map generated from a raw data file and displayed in the Carlson Survey program. (Courtesy Carlson Software)

Civil Drafting Technology