Chapter 5 Topographical Map| Class 11 Geography

Topographical Map Notes: Topographical Map is an important topic in CBSE Class 11 Geography. Chapter 5 Geography covers mountains, valleys, and other land features. They use lines called contour lines to show how high or low the land is. Topographical maps also include human-made things like roads and buildings. We can use these maps to understand the land better, find our way around, and plan cities. They help us see how people and nature interact with each other on the Earth’s surface. These notes help us understand and use topographical maps effectively.

All the important topics have been compiled in CBSE Notes Class 11 Geography Chapter 5: Topographical Map.

Chapter 5 Topographical Map| Class 11 Geography

Topographic Map

Topographical maps, also known as general purpose maps, provide detailed representations of geographic features at relatively large scales. These maps showcase essential natural and cultural elements like terrain relief, vegetation, water bodies, cultivated land, settlements, and transportation networks. These maps are prepared and published by the National Mapping Organisation of each country. In India, topographical maps are available in two series: the India and Adjacent Countries Series and The International Map Series of the World.

India and Adjacent Countries Series: The Survey of India was responsible for preparing topographical maps under the India and Adjacent Countries Series until the Delhi Survey Conference in 1937. After this conference, the Survey of India ceased the preparation of maps for neighboring countries and focused solely on creating maps for India according to the specifications outlined for the International Map Series of the World. However, the Survey of India retained the numbering system and layout plan of the abandoned India and Adjacent Countries Series for the new series of topographical maps.

International Map Series of the World: The International Map Series of the World aims to produce standardized maps for the entire globe at scales of 1:10,00,000 and 1:250,000.

Methods Of Relief Representation

The surface of the Earth is diverse, ranging from mountains to hills, plateaus, and plains. These variations in elevation and depressions are known as physical or relief features of the Earth. A map that illustrates these features is called a relief map.

Contours

Contours are imaginary lines connecting points of equal elevation above mean sea level. A map displaying the landform of an area using contours is called a contour map. The contour method is highly versatile and provides valuable insight into the topography of an area.

Traditionally, ground surveys and leveling methods were used to draw contours on topographical maps. However, the advent of photography, particularly aerial photography, has replaced conventional surveying, leveling, and mapping methods. Nowadays, aerial photographs are widely used in topographical mapping.

Contours are drawn at different vertical intervals (VI), such as 20, 50, or 100 meters above mean sea level, known as the contour interval. This interval is typically constant on a given map and is expressed in meters. While the vertical interval between two successive contour lines remains constant, the horizontal distance varies depending on the slope gradient. This horizontal distance, also called the horizontal equivalent (HE), is larger on gentler slopes and decreases with steeper slopes.

Some fundamental characteristics of contour lines include:

1. Each contour line represents points of equal height.
2. The shape and spacing of contour lines indicate the height and slope of the landform.
3. Closely spaced contours signify steep slopes, while widely spaced contours indicate gentle slopes.
4. When two or more contour lines merge, they represent vertical features like cliffs or waterfalls.
5. Contours of different elevations typically do not intersect.

Drawing of Contours and Their Cross Sections

We know that all the different parts of the Earth’s surface have different kinds of slopes. For example, flat areas like plains have gentle slopes, while places like cliffs and gorges have very steep slopes. Valleys and mountain ranges also have slopes of varying degrees, ranging from gentle to steep. So, the spaces between contour lines on a map are really important because they show us how steep the slope is.

Types of slope

Slopes on maps can be sorted into several categories: gentle, steep, concave, convex, and irregular or undulating. Each type of slope has its own distinct pattern of contour lines.

1. Gentle Slope: When a feature has a very slight angle of slope, it’s considered a gentle slope. On maps, you’ll notice that the contour lines representing this kind of slope are spaced far apart.
2. Steep Slope: Features with a high angle of slope are termed steep slopes. On maps, these slopes are shown with closely spaced contour lines.
3. Concave Slope: This type of slope has a gentle gradient in its lower parts and becomes steeper towards the top. On maps, the contour lines are spaced widely in the lower sections and closely spaced in the upper sections.
4. Convex Slope: Unlike concave slopes, convex slopes are gentler at the top and steeper at the bottom. Consequently, on maps, you’ll observe widely spaced contour lines in the upper parts and closely spaced lines in the lower parts.

Types of Landform

1. Conical Hill: A conical hill rises uniformly from the surrounding land. It typically has a narrow top and a slope that remains consistent. On maps, you’ll see concentric contours spaced almost regularly to represent this type of hill.
2. Plateau: A plateau is a vast, flat-topped highland with relatively steep slopes, towering above the adjacent plain or sea. The contour lines outlining a plateau are usually closely spaced at the edges, while the innermost contour may show a wide gap between its two sides.

Valley

Valley: A valley is a geological feature situated between two hills or ridges, formed due to lateral erosion by rivers or glaciers.

‘V’-shaped Valley: Resembling the letter V, this type of valley is commonly found in mountainous regions. The innermost contour line represents the lowest part of the V-shaped valley, with a very small gap between its two sides. Contour lines increase uniformly in value outward from this point.

‘U’-shaped Valley: Formed by intense lateral erosion from glaciers at high altitudes, a U-shaped valley has a wide, flat bottom and steep sides, resembling the letter U. The innermost contour line shows a wide gap between its two sides, with contour values increasing uniformly outward.

Gorge: Gorges are deep and narrow river valleys with steep sides, formed in high-altitude areas where vertical erosion by rivers is dominant. On maps, gorges are represented by closely-spaced contour lines, with the innermost contour showing a small gap between its two sides.

Spur: A spur is a protrusion of land extending from higher ground into lower areas. On maps, spurs are represented by V-shaped contours, with the apex of the V pointing towards the lower ground.

Cliff: Cliffs are steep or nearly perpendicular landforms. On maps, cliffs are identified by closely-spaced contour lines that merge into one another.

Waterfall and Rapids: A waterfall is a sudden descent of water from a considerable height in a riverbed, often accompanied by rapids upstream or downstream. On maps, waterfalls are depicted by contour lines that merge into one another, while rapids are shown by relatively distant contour lines.

Steps for Drawing a Cross-section

Here are the steps to draw cross-sections of various relief features from their contours:

1. Draw a straight line cutting across the contours on the map and label it as AB.
2. Place a strip of white paper or graph along the AB line.
3. Mark the position and value of every contour that intersects the line AB.
4. Choose a suitable vertical scale, like ½ cm = 100 meters, to draw horizontal lines parallel to each other and equal to the length of AB. Ensure that there are enough lines to accommodate all contour lines.
5. Mark the appropriate values corresponding to the contour values along the vertical scale of the cross-section, starting with the lowest value represented by the contours.
6. Align the edge of the marked paper with the horizontal line at the bottom of the cross-section so that AB of the paper corresponds to AB of the map, and mark the contour points.
7. Draw perpendicular lines from the AB line, intersecting contour lines, to the corresponding line at the base of the cross-section.
8. Connect all the marked points on different lines at the base of the cross-section smoothly to complete the drawing.

Identification Of Cultural Features From Topographic Sheets

Settlements, buildings, roads, and railways are vital cultural features depicted on topographical sheets using conventional signs, symbols, and colors. The location and distribution pattern of these features help in understanding the mapped area.

Distribution Of Settlements:

The map displays settlements through their site, location pattern, alignment, and density. Comparing the settlement map with the contour map aids in understanding various settlement patterns.

Types of Rural Settlements:

1. Compact
2. Scattered
3. Linear
4. Circular

Types of Urban Centres:

1. Cross-road town
2. Nodal point
3. Market centre
4. Hill station
5. Coastal resort centre
6. Port
7. Manufacturing centre with suburban villages or satellite towns
8. Capital town
9. Religious centre

Factors Determining Settlement Sites:

1. Source of water
2. Provision of food
3. Nature of relief
4. Nature and character of occupation
5. Defense

Site Examination: The contour and drainage map are essential for closely examining settlement sites. Settlement density is linked to food supply. Linear settlements, spread along features like river valleys, roads, embankments, and coastlines, are common.

Urban Settlement Patterns: In a cross-road town, houses align along roads, with the town center and main market at the crossing.

Interpretation Of Topographical Maps

Understanding map language and having a sense of direction are crucial for interpreting topographical sheets. Begin by locating the northline and scale to orient yourself. Familiarize yourself with the legends/key depicting various features, as all topo-sheets contain a table showing conventional signs and symbols.

Interpreting a Topographic Sheet:

(a) Marginal Information:

Includes sheet number, location, grid references, extent, scale, and covered districts.

(b) Relief and Drainage:

Hills: Identify concave, convex, steep, or gentle slopes and shapes.

Plateaus: Note if they are broad, narrow, flat, undulating, or dissected.

Plains: Recognize types like alluvial, glacial, karst, coastal, or marshy.

Mountains: Assess general elevation, peaks, passes, etc.

(c) Drainage:

Identify important rivers, tributaries, valleys formed, and drainage patterns like dendritic, radial, ring, trellis, or internal.

(d) Land Use:

Natural Vegetation and Forest: Determine density and categories like Reserved, Protected, Classified/Unclassified.

Agricultural, Orchard, Wasteland, Industrial: Identify land use categories.

Facilities and Services: Locate schools, colleges, hospitals, parks, airports, electric substations, etc.

(e) Transport and Communication:

Identify means of transportation such as highways, district roads, railways, waterways, and major communication lines.

(f) Settlement:

Rural Settlements: Recognize types and patterns like compact, semi-compact, dispersed, or linear.

Urban Settlements: Identify types and functions like capital cities, administrative towns, religious towns, port towns, or hill stations.

(g) Occupation:

Understand the general occupation of the area’s people based on land use and settlement types. For example, agriculture predominates in rural areas, while services and business dominate in cities and towns.

Map Interpretation Procedure

Map interpretation involves understanding the causal relationship among various features shown on the map. For instance, the distribution of natural vegetation and cultivated land can be better understood considering the landform and drainage. Similarly, settlements distribution can be examined in relation to the transport network system and topography.

Steps for Map Interpretation: –

Identify Location and Scale:

Determine the area’s location in India using the topographical sheet’s index number.

Note the map’s scale and contour interval to understand the extent and general landform.

Trace Out Features:

Use tracing sheets to identify major landforms, drainage features, land use areas (like forest, agriculture, sanctuary), settlements, and transportation patterns.

Describe Distribution Patterns:

Analyze the distribution pattern of each feature separately, focusing on key aspects.

Superimpose Maps:

Overlay pairs of maps to observe relationships between different patterns. For example, overlaying a contour map over a land use map reveals the relationship between slope and land use type.

Related Links

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4. CBSE Notes Class 10 Geography Chapter 1- Resources and Development

Topographical Map- FAQs

What is a topographical map?

A topographical map is a detailed representation of the Earth’s surface, showing various natural and cultural features such as relief, vegetation, water bodies, settlements, and transportation networks.

Who prepares topographical maps in India?

Topographical maps in India are prepared by the Survey of India, the national mapping organization.

What are the different series of topographical maps in India?

Topographical maps in India are prepared in two series: India and Adjacent Countries Series and The International Map Series of the World.

What features are depicted on topographical maps?

Topographical maps depict a range of features including relief (elevation), vegetation, water bodies, cultivated land, settlements, transportation networks, etc.

How are relief features represented on topographical maps?

Relief features such as mountains, hills, plateaus, and plains are represented using contour lines, which connect points of equal elevation above sea level.