Such points mark the limits of the contour on the map, but the contour does not end at those points. Closely spaced contour lines represent steep slopes, conversely, contour lines that are spaced far apart represent gentle slopes. Contour measuring instruments explanation of surface characteristics. The principal characteristics of contour lines which help in plotting or reading a contour map are as follows. Contours contours have the following significant characteristics. If the line indicates a depression, this fact is sometimes shown by a succession of short hachure lines, drawn perpendicular to the inner side of the line. But by counting up from 700 we can see that it lies between the 760 and 780 contour lines. Contour crenulations should conform to reentrants fig. Topographic survey topographic survey the most common method of representing the topography of an area is to use contour lines contours a contour lineis an imaginary level line that connects points of equal elevation topographic survey there are several rules to note when viewing topographic maps.
A contour line must never simply end, except at the edge of the map. The change in elevation between one contour line and the next. Two contour lines on the north side of the centre hill are touching or almost touching. Contour contour is an imaginary line on ground joining points of equal or constant elevations. A contour is perpendicular to a line of the steepest slope.
Objective of lesson 1 is to explain contour, its characteristics and graphical representation. Imagine a land surface inundated by the sea to a depth of 100 feet 30. Contour interval is the difference in elevation between two adjacent contour lines. Contour elevation numbers indicate the direction of elevation by always reading pointing uphill. All points along the same contour line are at the same elevation.
A set of ring contours with higher values of contour inside and lower values outside represents a hill and if the higher values are outside and lower values inside then it represents a depression like a pond. When a contour line is drawn on a map it represents a given elevation. A contour or a contour line may be defined as the line of intersection of a level surface with the surface of ground. Evenly spaced contour lines indicate a uniform slope. The contour lines are interpolated on the assumption that there is uniform slope between two points on two adjacent contours.
On a map the contour lines will be spaced closer together with a decline in height above sealevel. The physical characteristics of line the physical characteristics of line are many. All points on the contour line are at the same elevation. Features of contour lines are helpful in plotting and interpretation of several features in the map. They may use the same sheet of paper to create these drawings. Concave slope a slope which becomes progressively steeper uphill. The elevation represented by contour lines is the vertical distance above or below sea level. In other words, contour is a line in which the ground surface is. They, like valleys, have higher ground in three directions and lower ground in one direction. Contour lines trend up valleys and form a v or a u where they cross a stream. The number of such lines should be equal or more than the total contour lines. The following are advantages and disadvantages of using contour as the method of representing relief on the mapped area, starting with advantages.
Characteristics of contour lines a contour line is a line of equal elevation. Characteristics of contours i all points in a contour line have the same elevation. It depends upon the scale of the map, nature of the ground and. On contour lines the level of lines is also written. Standards expanded surface texture parameters and curves filtering process of iso5651. Chapter 2 reading topographic maps and making calculations. Illuminated contour lines additionally vary color based on an angle of illumination.
A point on a map or chart that has the elevation noted. The closer together the lines are, the steeper the slope. Contour map download free geography activity jumpstart. A contour line must represent one and only one elevation. A contour map helps its users to identify altitudes, heights, density, and depth of an area. Point c 770 point c is not directly on a contour line. Characteristics of contour lines, contouring, assignment help. Zeroelevation contour lines near the oceans were deleted. Their contour line us point away from higher ground. On usgs maps, contour intervals are usually 1, 5, 10, 20, 40, and 80 feet. Generating contour lines using different elevation data. On a map the contour lines will be spaced closer with an increase in height above sealevel.
On some maps, numbers on the lines will let you know what the elevation is for that line. From above we know the contour interval is 20, so if we count up two contour lines i. A contour is a line drawn on a map that joins points of equal height above sea level. This was a practical way of dealing with imperfect ned data along the coastline, as well as eliminating. Ask the students to trace with their fin gers around the 40foot contour line on the map. Every point on the map touching the line should be the same elevation. A contour may be represented as an ordered list of edges or by a curve. Then ask them to look at the picture of the hill and draw their fingers around the 40foot contour line. It also helps the users to identify the type of soil and settlement found in that region. Contour lines mark points of equal elevation on a map and are critical to. It is, essentially, the outline or silhouette of a given object or figure.
This means every point on a contour line has the same altitude as that of the assumed intersecting surface. The contour lines in an area are drawn keeping difference in elevation of between two consecutive lines constant. A contour may close within a map, or it may be discontinued at any two points at the borders of the map. Look for the height and shape of the ground which is shown on 1. Pu 09,10,14 contour interval ci it is the vertical distance between any two consecutive contours. All points on a given contour have the same elevation. Contour lines characteristics of contour lines are. Contour are lines drawn in the map to show the areas with equal altitude from sea level. A detailed guide to contour lines, formations, drawings, hills and depressions.
Readingunderstanding topographic maps school of forest. Closed contours with arrow in the centre represent depressions. A line drawn on a map or plan connecting points of equal elevation. A map where contour lines, along with other topographical features, are drawn to depict a certain terrain or area is called a topographical or contour map. Contour lines are the most common method of showing relief and elevation on a standard topographic map.
All points on a contour line are of the same elevation. Then ask the students to draw their fingers along the 20foot contour line on. Compared with straight line planting, the practice reduces fertilizer loss and increases crop yields on uneven terrain. Contour lines isolinesand imaginary line in the map. Their contour line us and vs point toward the higher ground. Imaginary line joining points of equal elevation above or below a datum contour lines have a specific contour interval interval is the vertical distance between contours ci is a. A contour line is an imaginary outline of the terrain obtained by joining its points of equal elevation. Visual characteristics of tanakas relief representation method through observa. The column and row indices of z are the x and y coordinates in the plane, respectively. Representing heights on maps professor keith clarke contours on maps. All contour lines eventually connect with themselves. Heres a list of contour lines types of imaginary line in the map you might discover as you explore geography. In cartography, contour lines are an imaginary line of a terrain that joins the point of equal elevation above a given level, such as mean sea level or benchmark. So two different contour lines cannot intersect or otherwise contact each other except at a point where a vertical or overhanging surface, such as a vertical or overhanging face of a cliff, exists on the ground figure 818 shows an overhanging cliff.
The chart facing page 22 shows the standard symbols used on the topographic maps of the survey. Open contours also occur when line fragments are linked togetherfor example, when line fragments are linked along a stroke in a drawing or sample of handwriting. Changing contours indicates a change of ground form. Contour line, a line on a map representing an imaginary line on the land surface, all points of which are at the same elevation above a datum plane, usually mean sea level. Use contour lines to determine elevations of mountains and. Mark the position and value of every contour that cuts the line ab. A contour is defined as an imaginary line of constant. Drawing art, learning drawing techniques block museum. If the contour interval is not printed on the map, it can be calculated which is discussed later in this chapter.
Each drawing below violates a rule of contour lines. Suppose a map includes contour lines of 100m, 98m,96 m and so on. Examples of curves include line segments and cubic splines. A map showing contour lines is known as contour map. A beginners guide to understanding map contour lines os. This line on the map represents a contour and is called contour line. In the world of art, a contour line is a line which defines a form or an edge. Contour map a map showing contour lines is known as contour. Draw a line between the two points bounding the desired profile area. Contour lines must close, not necessarily in the limits of the plan. Mark four points two on the endpoints, and two between and draw the contours. Now use the contour line drawing method to create an outline drawing of the stilllife on another sheet of 18x 24 paper. A contour line represents an imaginary line on the ground, above or below sea level. Contour lines can also be used to depict dramatic changes of the plane within the form.
A contour must close itself in the map or must go out of the boundaries of the map. From each mark, indicate the vertical height with a dot on a scale. They never cross, split or intersect at a cliff they might merge. How to read and understand topographical maps for trails and hiking while backpacking or in a survival situation. Lines may be short or long, thin or thick, straight or curved, direct or meandering, zigzag or serpentine, distinct or blurred. So two different contour lines cannot intersect or otherwise contact each other except at a point where a vertical or overhanging surface, such as a vertical or overhanging face of a cliff, exists on the.
A single contour line can not lie between two lines of higher or lower elevation. Creation of digital contours that approach the characteristics of. Vertical distance between any two consecutive contours is known as the contour interval. In cartography, contour lines are an imaginary line of a terrain that joints the point of equal elevation above a given level, such as mean sea level or benchmark. An imaginary line on the ground surface joining the points of equal elevation is known as contour. Other features are shown by a variety of conventional signs, symbols, lines, and patterns, which are printed in appropriate colors and identified by names, labels, and numbers. Divide 300 feet by 3 to get one contour every 100 feet. Contour farming, the practice of tilling sloped land along lines of consistent elevation in order to conserve rainwater and to reduce soil losses from surface erosion. Depression contours should not cross single line streams more than once. Contour drawing does not have to be that simplistic, however. Contour measuring instruments explanation of surface. No two lines meet on intersect each other in any case. Contour lines types, characteristics and uses in surveying. The horizontal distance between any two contour lines indicates the amount of slope and varies inversely on the amount of slope.
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