Pdf contours maps such as topographic maps compress the information. Also remember the closer contour lines are together, the steeper the slope. The chart facing page 22 shows the standard symbols used on the topographic maps of the survey. Topographic survey topographic survey topographic survey. In our apple example, you might add a little curve that indicates the indentation where the stem forms. Have them subtract the lowest number from the highest to figure out the height of that landform. Contour map a map showing contour lines is known as contour map. But before we are discussing about drawing contour lines in qgis, lets start talking a little bit about the concept of contour line, what contour line definition is, contour lines characteristics and and how the method in drawing contour line. 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. This tutorial will discuss how to create contour lines in qgis. In other words, contour is a line in which the ground surface is intersected by a level surface obtained by joining points of equal elevation. Use contour lines to determine elevations of mountains and. Contour drawing does not have to be that simplistic, however. Jan 18, 2015 the concept of contour lines eclassroom tour lines the concep t of con tour lines.
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. Display the usgs topographic map symbols pdf for students. Contour lines must close, not necessarily in the limits of the plan. A traverse station is each of the points of the traverse, while the traverse leg is the straight line between consecutive stations. Some thoughts on topographic habitat characteristics.
A contour line is an imaginary outline of the terrain obtained by joining its points of equal elevation. Features of contour lines are helpful in plotting and interpretation of several features in the map. It is, essentially, the outline or silhouette of a given object or figure. Contour lines allow you to infer general terrain characteristics from. Contour lines contour line interpolation free 30day. Contour lines software free download contour lines top 4. All points in a contour line have the same elevation. Langbein and others abstract river floods are the result of many causes, and one of the primary objectives of scientific hydrology is the segregation and evaluation of the causative factors. A series of vshape indicates a valley and the vs point to higher elevation. The objectives of contour analysis and visualization can be described in the following stages 1.
They never cross, split or intersect at a cliff they might merge. Maps are flat unlike some of the ground which they represent so we use contour lines on a map to show how high the ground is. The gradient of the function is always perpendicular to the contour lines. Depression contours should not cross singleline streams more than once. The software will generate contours at all intersection points of a fence selection and contour line. On a map the contour lines will be spaced closer with. Their contour line us point away from higher ground. Along plane surfaces, contour lines are straight and parallel. Contours are imaginary lines joining places having the same elevation above mean sea level. A line drawn on a map or plan connecting points of equal elevation. They, like valleys, have higher ground in three directions and lower ground in one direction. What do the contour lines on your map tell you about the topography or scenery of the area. This line on the map represents a contour and is called contour line. Two contour lines on the north side of the centre hill are touching or almost touching.
Contour lines can also be used to depict dramatic changes of the plane within the form. Flat ground is indicated where the contours are widely separated and. Contour map download free geography activity jumpstart. It is a plane section of the threedimensional graph of the function fx, y parallel to the x, yplane.
Introduction to contour maps national geographic society. Characteristics of contours i all points in a contour line have the same. Divide 300 feet by 3 to get one contour every 100 feet. Explorer website to find and display a contour map of your area. A contour map helps its users to identify altitudes, heights, density, and depth of an area.
The distance between contour lines indicates the steepness of the slope. Contour lines do not cross each other but there are 2 exceptions. 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. It is, however, unlike outline, which only states the outside edge of an object defining difference between positive and negative space. Imaginary lines joining all the points of equal elevation or altitude above mean sea. Contour lines types, characteristics and uses in surveying. Characteristics of contour lines a contour line is a line of equal elevation. These contour datasets were generated from the national elevation dataset ned and the national hydrography dataset nhd in a fully automated process. Representing heights on maps professor keith clarke contours on maps. The change in elevation between one contour line and the next. A contour line must never simply end, except at the edge of the map. Pdf contour lines generation in karstic plateaus for. Changing contours indicates a change of ground form.
Use symbols to identify other features on the contour map of your area. Characteristics of contours there are a few simple rules about contour lines to keep in mind as you analyze and interpret topographic maps. If text labels are overlapping on the contour line, then reading the contour lines becomes difficult after printing the. Smoothly join all the points marked on different lines at the crosssection base. Hachures are short lines perpendicular to the contour line. Data layers with gis software, you can digitally represent geographic objects with a variety of shapes and layer those shapes on top of one. Another way of thinking about contour lines is as a tide mark left by the sea as the tide goes out, leaving a line every 5 metres. Contour lines characteristics of contour lines are. Pdf contour lines are a key features of topographic maps as they make the comprehension of terrain more easy.
Using the basic principles of slope, shape and altitude, it is possible to identify a wide range of physical landforms on maps. Pu 09,10,14 contour interval ci it is the vertical distance between any two consecutive contours. Characteristics of contour lines, contouring, assignment help. The contour lines in an area are drawn keeping difference in elevation of between two consecutive lines constant. Evenly spaced contour lines indicate a uniform slope. The contour lines on a map provide a useful insight into the topography of an area. A 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.
The closer together the lines are, the steeper the slope. The concept of contour lines models and landscape maps with landscape features. Mark four points two on the endpoints, and two between and draw the contours. More generally, a contour line for a function of two variables is a curve connecting points where the function has the same particular value. Following are the characteristics of contour lines in surveying for reading contour maps. Now use the contour line drawing method to create an outline drawing of the stilllife on another sheet of 18x 24 paper. Isolines, also referred to as contour lines, can be used to represent elevation on a map by connecting points of equal elevation, for instance. Compared with straight line planting, the practice reduces fertilizer loss and increases crop yields on uneven terrain. But the second route has widelyspaced spaced contour lines. A contour line is a single, clean, incisive line, which defines edges. Continuous dont split or cross indicate infinite number of points of equal elevation. The contour interval for a quad is the larger of the. 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.
Their contour line us and vs point toward the higher ground. Contouring the process of tracing contour lines on the surface of the earth is. These imaginary lines provide a good visual representation of the terrain. Drawing art, learning drawing techniques block museum. On a map the contour lines will be spaced closer together with a decline in height above sealevel. The greater the distance between two contours the less the slope. If youre looking for topographic maps for the united states, the first place to look is the usgs topo maps series. They can be smooth or flowing, short or choppy, dark or light, broad or narrow. A contour line must represent one and only one elevation. Explain to students that these are imaginary lines that join points of equal elevation, and.
A topographic map bingham canyon area in utah with contour lines spaced in a contour interval of 50 feet apart. Concave slope a slope which becomes progressively steeper uphill. The way in which contour lines are arranged, allows us to identify certain landforms and features in the terrain. The elicited contour semantics comprises four key concepts contour regions, contour lines, contour values, and. Imagine a land surface inundated by the sea to a depth of 100 feet 30. But if you picked the first route, youre the type of free climber who scales mountains with just a pick axe. Visualize the contour lines in 3 dimensional view application. How to download usgs topo maps for free gis geography. Contour crenulations should conform to reentrants fig. 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. Draw perpendiculars from ab line, intersecting contour lines, to the corresponding line at the crosssection base.
A beginners guide to understanding map contour lines os. The diagram illustrates how contour lines show relief by joining points of equal elevation. Remember contour numbering reads up hill in other words the top of the number is uphill and the bottom is downhill. On a map the contour lines will be spaced closer with an increase in height above sealevel. 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. Characteristics of contours there are a few simple rules.
Pdf automated placement of supplementary contour lines. Contour elevation numbers indicate the direction of elevation by always reading pointing uphill. 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. 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 function of scale and units. 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. In cartography, a contour line often just called a contour joins points of equal elevation. By following a contour line on the ground, you would travel neither uphill nor downhill, eventually ending up back at your starting point. Have students read the contour lines at the bottom and top of the highest place in your area.
Contour lines can indicate the outer borders of the foot and suggest a threedimensional form. In the world of art, a contour line is a line which defines a form or an edge. A line marked 6500, for example, means that point on the map is 6,500 feet above sea level. On contour lines the level of lines is also written. Draw an imaginary line on the contour map in a way it intersects contour lines where you wish to annotate contours. As with all isolines, when contour lines lie close together, they represent a steep slope. Based on spatial relation theory and geometric characteristics of contours, qiao et al. Suppose a map includes contour lines of 100m, 98m,96 m and so on. Characteristics of contour contours of different elevations cannot cross each other caves and overhanging cliffs are the exceptions. For instance, is there a river valley, cliff, or desert plain. Consider the characteristics of contour lines discussed in lab.
This includes hydrography, place names, contour lines and cultural features of the nation. Contour lines mark points of equal elevation on a map and are critical to understand the elevation profile of your terrain. The ned data were modified by the nhd flow lines, areas, and water bodies to facilitate improved integration between the hypsography and hydrography. Joining two while bearing and distance is known as traverse. 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. Which hiking trail would you take for the slowandsteady climber, youd pick the second route because widelyspaced contour lines mean the slope is gradual. The column and row indices of z are the x and y coordinates in the plane, respectively. Matlab automatically selects the contour lines to display. The method of showing relief features through contour is very useful and versatile. Steepest slope is shortest distance between contours. They may use the same sheet of paper to create these drawings. Contour lines software free download contour lines top 4 download offers free software downloads for windows, mac, ios and android computers and mobile devices. These contour lines are an important way of showing the rise and fall of the land on a map. A contour map gives an idea of the altitudes of the surface features as well as their relative positions in plan serves the purpose of both, a plan and a section.
This feature class was derived from the cartographic feature file cff. Since 1884, the purpose of these general use maps has been to display the complex, changing geography of the united states. The contour interval of a contour map is the difference in elevation between successive contour lines. Topographic characteristics of drainage basins by walter b. How to read and understand topographical maps for trails and hiking while backpacking or in a survival situation. Contour lines show all the places that are the same height above sea level. A point on a map or chart that has the elevation noted. Depression contours should not cross single line streams more than once. Interpolation of contours usually 110th of the contour interval are drawn. Every point on a contour line is of the exact same elevation. The contour interval is 20 meters figure 102, thus each one of the intermediate contour lines crossed to get to point a adds 20 meters to the 500meter index contour line. There are many fields of interest in which contour analysis and visualization can be applied.
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