Define edge line and contour interval.Describe the rule of contour lines.Overview of edge Lines

Watch this video which explains plenty of of the principles of edge lines. We will certainly use plenty of of these concepts in this module.

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Contour Lines and also Contour Interval

Figure 6 mirrors a section of a contemporary topographic map. The brown lines are contour lines.

Figure 6. A section of a topographic map, consisting of the contour interval label.

On topographic maps, every contour line connects points in ~ the very same elevation. The contour interval is the distinction in elevation between surrounding contour lines.

The elevation for each contour line is sometimes marked on the line. To avoid clutter, not every edge is labeled. The key of an unlabeled contour line have the right to be identified by learning the edge interval and also looking at adjacent contour lines. The key of a point located in between two contour lines deserve to be estimated by interpolating in between the lines. If a allude is halfway in between two contour lines, it will be about halfway between the elevations the those 2 contour lines.

In the US, standard topographic maps have elevation marked in feet above mean (average) sea level. However, global maps and also maps of elevation of the s floor (bathymetry) are often significant in meters.

There room a pair of clues that will help you identify the elevation units on a map. First, the legend or information around the in salt of the map might say something choose “contour expression = 20 feet” or “contour expression = 20 meters.” Maps the use systems of feet because that elevation may note contour lines through units such as 400′. The ‘ shows units that feet.

Rules of contour LinesEvery allude on a contour line is that the specific same elevation. In various other words, edge lines attach points of same elevation.By definition, contour lines different points of higher elevation native points of reduced elevation. This way it is always possible to define an “uphill” direction top top one side of a contour and also a “downhill” direction ~ above the various other side.Contour lines never ever cross.  They may come an extremely close come each other (e.g. Along a cliff), but by an interpretation they might never cross every other.* This is because one place on the surface ar of planet cannot be in ~ two different elevations!Contour lines never ever split. Instead, contours type closed loops. These loops follow the form of the land, and also may prolong past the leaf of the map.Closely spaced contours indicate a steep slope, whereas border that are spaced far apart show a gentle slope or almost flat surface.

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Figure 7. An untrue topographic map.