Chapter 2 reading topographic maps and making calculations. Colors and symbols are used to represent other features on the land. In this video, you are going to learn how to read and to use the contour lines on a map. The way in which contour lines are arranged, allows us to identify certain landforms and features in the terrain. Laser levels can help find the contour lines of a property, and major league digging equipment can be brought in to quickly, painlessly at least from the human side of things excavate.
A topographic mapis a representation of a threedimensional surface on a flat piece of paper. Understanding contour lines topo maps just look like a childrens drawing if you dont know what contour lines are. They never cross, split or intersect at a cliff they might merge. Contour patterns the relationship between higher and lower contours and the distance between them can give you valuable clues about what the real surface of the ground is like. Contour lines identify all of the areas on the site that are at a certain elevation and how.
Many maps have either a 40 or 80foot contour interval. If you trace the length of a line with your finger, each point. Each drawing below violates a rule of contour lines. They run perpendicular to the direction of the slope. Use contour lines to determine elevations of mountains and. Every point on a particular contour line is at the same elevation. Contour lines fit together in many different ways, and they form shapes. Other than the obvious trails and rivers, these squiggly lines are contour lines. Now, contours apply lines along the contours of an objectand can be used in many situations. Theyre useful because they illustrate the shape of the land surface its topography on the map. Contour lines are con nuous lines used on a topo map in order to show points of. The last special sketch and toon line type well coveris contour lines. To fully understand what each type of marking, boundary, and symbol represents refer to the official usgs topographic map symbols hadbook pdf.
A contour plot is a graphical technique for representing a 3dimensional surface by plotting constant z slices, called contours, on a 2dimensional format. The closer together the contour lines appear on a topographic map, the. An introduction to the shapes of landforms as shown on maps by contour lines. Even though all the lines look similar at first, they are describing very different landscape features. By understanding the contour of the land, scientists can determine how water and wind may cause erosion. Understanding the shape of the land by looking at a map is a very useful skill and can be essential if youre going to be walking in mountainous terrain. These skills will significantly help you draw natural forms from life and. In our apple example, you might add a little curve that indicates the indentation where the stem forms. Before getting into the technical knowledge of how to read a topographic map, heres a little history. This guide will help the user understand the basics of topographic maps.
In order to complete an earthwork analysis, the existing conditions need to be compared with the proposed conditions. Learn the use and meaning of contour lines on maps and understand how to use them on your map when youre planning routes or out and about. The height and shape of the land is shown on a map using contour lines. By following a contour line on the ground, you would travel neither uphill nor downhill, eventually ending up back at your starting point. Download understanding contour lines in pdf format download the free pdf resource. Pdf contours maps such as topographic maps compress the. To read the contour lines on a map, first note the direction your map faces. Mark four points two on the endpoints, and two between and draw the contours. On topographic maps, contours represent the shape of the land. Maps in mountainous areas may have contour intervals of 100 feet or more. They can help to establish conservation areas such as watersheds and wind blocks. For any given map, the contour interval is always the same within that map. Weather the topography of the land can have an impact on weather patterns. So lets go ahead and apply a sketch style tagto our landscape object right hereand well go and enable contours.
Ever noticed those squiggly lines all over your hiking map. The diagram illustrates how contour lines show relief by joining points of equal elevation. Can your students identify a plateau from a saddle or a steep slope from a spur. Topographic maps were invented by a man named john wesley powell, a union army veteran and geologist who in 1884 convinced congress to authorize a painstaking cartography project in which powells team would systematically create topographic maps to better understand the resource. The thin brown lines snaking around a topographic map are called contour lines. A line drawn on a map or plan connecting points of equal elevation. The change in elevation from one contour line to the next is always the same within the same map. Contour line contour is a slow, intense inspection of parts.
Look for students grasp of contour lines, and of how the lines represent real landform features. Put simply, contour lines mark points of equal elevation on a map. All contour lines eventually connect with themselves. It is meant for those who have had a problem comprehending exactly what they show and how they actually depict the topography. Rule 5 contour lines are closer together in steep terrain and farther apart in flat. A point on a map or chart that has the elevation noted. Find a hill top, a steep slope, and a gentle slope on the crosssection. Lines spaced further apart indicate flatter and gentler terrain. A perfect bullseye shape is created, indicating a circular mountain. Understanding contour line formations and how to read topographic maps. Advanced guide to reading contours and relief os getoutside. These lines are generally relative to mean sea level. This line types really versatileand a lot of fun to experiment with. The numbers on contour lines are always displayed in ascending height, so if the numbers increase it denotes an uphill slope, and if they decrease its a downhill slope.
This means that if you were to walk along the ground represented by a contour line, you wouldnt go up hill or down hill. Heres a cool way to understand how to interpret contour lines. If the contour lines are thicker and form a circle, this means there is a summit or peak. 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 above sea level. Understanding contour lines on a map learn about hiking. To better understand contour lines of equal sensitivity it is helpful to. If the contour lines are not thick and they form a circle, this means there is a hill. Understanding contour lines an introduction to the shapes of landforms as shown on maps by contour lines. The cartographer gets to play a giant game of connect the dots. The graphical depiction of the proposed conditions and. For me, however, the world of swales is a bit more rudimentary. The contour lines are very close together, indicating an extremely steep slope that rises from 4500 feet to 5100 feet that is about 2 football fields standing on end. The digital elevation model on the poster is helpful in understanding topographic maps. As a consequence of varying degrees of frustration mine as well as theirs, approximately three years ago, after teaching the standard approach to understanding topographic maps for nearly 20 years, i tried to put myself. Contour lines show elevation and the shape of the terrain.
The distance between contour lines indicates the steepness of a slope. This has the effect of dividing areas into shallower and deeper waters. A beginners guide to understanding map contour lines national map reading week. These lines appear as thin orange or brown lines with numbers on them. There are to be three contour lines on this interval. We walk through creating latitude and longitude lines and how cross contour lines change directions on a curved object. Contour lines contour lines connect places of equal altitude contour lines depict various landforms on a map by reading the contour lines we can determine what the terrain in an area looks like. Knowing these features and how they are typically depicted by contour lines is the key to extracting the most information from a topo map. All points along the same contour line are at the same elevation. Topographic maps identify terrain and elevation with the use of contour lines. Contour lines represent the shape and elevation of the land, such as ridges, valleys, and hills. Joe explains that contour lines connect points of equal height and that each is marked on a map by a number denoting height above sea level in. Changing contours indicates a change of ground form. Environment data from topography can help to conserve the environment.
A contour is a line that connects points of equal elevation. When contour lines are close together, the terrain is steeper. Earthwork basics and a traditional calculation method. Divide 300 feet by 3 to get one contour every 100 feet. Contour lines, sometimes called level lines, join points of equal elevation. For a massive swale, something more riverlike than what most of us will attempt, this makes sense. If you trace the length of a line with your finger, each point you touch is the same height above sea level. A beginners guide to understanding map contour lines os. At some point along that line, its exact elevation is listed. In the most basic form, an outline drawing is also called a pure contour. It is, however, unlike outline, which only states the outside edge of an object defining difference between positive and negative space. Being able to interpret how topographic features fit together in the landscape gives the user a much deeper understanding of the lay of the land and how to identify where they are and how to move through it.
They allow a person viewing the plan which is 2 dimensional to form an impression of its 3 dimensional shape. How to read and interpret topographic maps sole adventure. If you were to walk the path of a contour line in real life, you would remain at the same elevation the whole hike. If a hill is very steep the contour lines might even merge into each other. Join ej hassenfratz for an indepth discussion in this video, understanding the contour line options, part of creating motion graphics with sketch and toon in cinema 4d. Contour lines that form a series of circles on the map, where the circles get smaller and smaller, indicate a raised land mass. How to read and understand topographic maps scwibles.
Hills, slopes and mountains are represented on a map using contour lines. Contour lines that are far apart indicate there is a small change in vertical elevation given the horizontal distance. This is a short video explaining contour lines on a map. Earthwork analysis basics and a traditional calculation method. The change in elevation between one contour line and the next.
Readingunderstanding topographic maps school of forest. This picture shows how contour lines can be used on maps to describe different landscapes. In order for an engineer to grade the site, they must have an understanding of slope. The closer together the lines are, the steeper the slope. Illuminated and shadowed contour lines date back to the mid nineteenth. A contour is a line drawn on a map that joins points of equal height above sea level. The first step in understanding contour lines is to check out your maps legend to see what your contour interval is. Contour lines can also be used to depict dramatic changes of the plane within the form.
Use questions on the playdough topo student page to assess students ability to apply the concept of contours to a physical model. Understanding contour lines this is what the cartographer starts with. An 80foot interval simply means that each contour line is 80 vertical feet away from. That is, given a value for z, lines are drawn for connecting the x,y coordinates where that z value occurs.
Successful comprehension requires understanding that continuous elevation information is categorically encoded using contour lines, as well. A contour interval is the vertical distance in elevation between two contour lines. Using the basic principles of slope, shape and altitude, it is possible to identify a wide range of physical landforms on maps. Its very likely that youve been drawing contour lines all along because it is the simplest form of art. Its also important to note the contour interval, or distance in vertical feet, between contour lines. Illuminated contour lines additionally vary color based on an angle of illumination. Contour lines are there to give you an idea of what is happening beneath the waters surface. The spacing between the lines denotes the topography.
Contour lines will form shapes which define terrain features. Contour lines, often red, connect similar water depth listings. Most maps are oriented with north at the top of the map. A topographic map will tell you whether an area is steep or level. A contour line is a single, clean, incisive line, which defines edges. Put simply, for the entire area of the map they allow you to the answer the question. A contour line represents points of similar elevation height measured in metres. The contour interval is printed in the margin of each u. Understanding the contour line options linkedin learning. The closer together the contour lines, the steeper the slope of the hill.
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