Contour Mapping With Contour Lines
A contour line can also be called an isoline, isopleth, or isarithm. The lines are the function of two variables, a curve. Here the function has a constant value, here the curve joins the points of an equal value. Contour lines are plane sections of the dimensional graph.
In cartography, a contour line is normally called a ‘contour’. These lines join points having equal elevated heights, above a predetermined level, normally the sea level.
These contour lines often illustrate a contour map, which is the main topic of discussion in this specific content. For example, a topographic map, showing valleys and hills, its steepness or gentleness of the slopes is represented by the contour lines. We will vividly discuss Contour Mapping in our subsequent sections.
Contour Mapping
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First and foremost, we will answer ‘what is a contour map?’
A contour map is a type of map where the shape of the land surface is shown by the contour lines, the relative spacing done between these lines indicates the relative slope of the particular surface.
Contour map meaning is quite clear to us, if we further deduce this definition it means – this is the delineation of any property in the map which is formed by constructing lines. The lines are carved based on the equal values of that property which is available as data points.
In the contour map meaning, it can be said that contour mapping is a type of topography mapping, but to distinctly study the concept we will find there is an acute difference between the two, so we cannot use each other as synonyms. A topographic map is an accurate map that displays natural terrain and also man-made objects like buildings, roads, or bridges. While Contour maps represent changes in the elevation with the help of contour lines.
Each of the contour lines being marked on a map joins the points having an equal height. The method of contouring cannot be totally relied on because two investigators can produce different types of maps whenever interpolation between two data takes place.
Contour Mapping According to the Crustal Thickness
A contour map of global having the crustal thickness represents the bimodal division of the earth's crustal thickness. The ocean basins have 6 to 7 km thick crust (excluding 4 to 5 km of water). The continents have an average thickness measuring 39.7 km. The crust is generally 30 km measured for thickness in the ocean-continent margin and this gradually increases towards the continental interior towards 40 to 45 km. The crust which is thicker than 50 km is only to few regions, which includes the Tibetan Plateau located in western China, the Andes in western South America. The contour map shows merely the large-scale crustal features, hence the regions with locally thick crust are not visible in this map. The crust does not display the pattern of increased thickness with the increase in age, as this would be the case if the same were to be repeatedly subjected to the igneous intrusions which are from the underlying mantle. For example, the crust located in western Australia is older compared to that in central Australia, yet the crust is a minimum of 10 km thinner in western Australia. This crust has a thickness which is in excess of 50 km, this is almost a young and active mountain belt. These regions consist of high topography and are vulnerable to rapid erosion.
Contours Geography
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What is a Contour?
Contours are imaginary lines. These lines connect points of the same value. A contour map generally shows different contours such as the elevation or even the temperature contours.
Contours are the lines on a map that join the same height. The Contour interval refers to the variation in height, example the contours are drawn at every meter.
Contour lines on a map basically illustrate the height of a distinct place. This also helps us to obtain information regarding the steepness of the slopes, which is along the direction of the land that is sloping.
The contours here form patterns representing how steep the slopes actually are. The closer the contour lines are stuck together; the steeper is the slope.
With this result, we can study the relief of the land; whether this is a valley, a mountain, a valley which has a flat floor, also we can study if the valley has a stream, or not, or is it around the cone-shaped hill or a hilltop.
Uses of Contour Mapping
The Contours provide important information which can help us to study the nature of the terrain. This proves to be useful for the selection of sites, to determine the catchment area of a drainage basin, or to find intervisibility between two or more stations, etc. Some of the uses of contours are described below.
Nature of Ground
To study the nature of the ground which catches interest.
To Locate Route
To identify the route, a contour map provides worthy information on how to locate a route.
Intervisibility Between Stations
When the intervisibility between the two points cannot be easily ascertained by inspecting the area, then the contour map comes to the rescue.
To Determine Catchment Area or Drainage Area
The catchment area of a particular river can be well determined by using the contour map. The watershed line very well indicates the drainage basin of the river which passes through the ridges and then saddles of the terrain that turns around the river. It is always perpendicular to the contour lines. The catchment area which is contained between this watershed line and the river outlet is measured with a planimeter.
FAQs on Contour Mapping
1. What exactly is contour mapping in geography?
Contour mapping is a method used on maps to show the shape and elevation of the land. It uses special lines, called contour lines, to connect points of equal height. This helps us visualise a three-dimensional landscape, like hills and valleys, on a flat, two-dimensional map.
2. What do the lines on a contour map represent?
Each line on a contour map, known as a contour line, represents a specific height above sea level. Every single point along one line is at the exact same elevation. By reading these lines, you can understand the topography or the 'lay of the land'.
3. How can you tell if a slope is steep or gentle just by looking at a contour map?
You can understand the steepness of a slope by looking at the spacing of the contour lines.
- When lines are drawn very close together, it indicates a steep slope.
- When the lines are far apart, it shows that the slope is gentle and gradual.
4. What is the importance of the 'contour interval' on a map?
The contour interval is the constant difference in elevation between two consecutive contour lines. It is important because it tells you how much height you are gaining or losing as you move from one line to the next. For example, a contour interval of 20 metres means each line is 20 metres higher or lower than the one next to it.
5. Why can contour lines never cross or touch each other?
Contour lines can never cross because one point on the ground cannot have two different elevations at the same time. Crossing lines would imply an impossible physical feature. The only rare case where they might appear to merge is at a vertical cliff, where the slope is nearly 90 degrees.
6. How do contour maps show common landforms like a hill or a valley?
Contour maps use distinct patterns to represent different landforms:
- A hill is shown by a series of closed circular lines with the elevation increasing towards the centre.
- A valley is typically shown by V-shaped contour lines. The point of the 'V' always points upstream, towards higher ground, indicating the path where water would flow down.
7. What are some real-world examples of how contour mapping is used?
Contour maps have many practical applications in the real world. For instance:
- Engineers use them to plan routes for roads and railways, avoiding areas that are too steep.
- City planners use them to select suitable sites for building dams and reservoirs.
- Hikers and military personnel use them for navigation to understand the terrain ahead.
