Topographical Maps: Features and Use of Colors

Topographical Maps Introduction

• Topographical maps detail natural ground features like topography, drainage, and vegetation
• Urban settlements, roads, and railways are also shown based on the map scale
• These maps provide specific details, including the names of geographical features like hills, mountains, plateaus, villages, and towns
• Also includes ports, rivers, and forests, alongside symbols for official places, rest houses, and mines
• Topographical survey sheets are intended to vividly represent an area in miniature form
• The British established the Survey of India Department in 1767
• Major James Rennell was appointed as the first Surveyor General of India
• Maps of India and nearby countries were commonly prepared at a scale of 1:10,000,000
• These maps were known as 'one million maps', covering over 5 million square miles
• Mt. Everest is named after Sir George Everest, who conceived Trigonometrical Survey

Use of Colours on Topographical Sheets

• Topographical maps use different colors to portray natural, man-made, and cultural
• Symbols and their meanings are explained in the map's legend
• Green represents forests, grasslands, scattered trees, and orchards
• Yellow indicates cultivable land and plains
• Blue shows perennial wells, streams, tanks, lakes, ponds, and general water bodies
• Brown marks contour lines, heights, and relief features like mountains and hills
• White indicates rocky, bad, or uncultivated land
• Black signifies dry streams, surveyed tree heights, river banks, broken ground, railways, and telephone lines
• Red denotes permanent huts, settlements, cities, grid lines, and roads

Relevance of GPS and GIS

• Geographical Positioning System (GPS) and Geographical Information System (GIS) can locate any destination
• Topographical maps are invaluable as information storehouses

Map Scale and its uses

• A map scale uses a measuring line to show the relationship between distances on a map
• Scale shows actual distances on the ground
• Scale is the "ratio between a distance measured on a map
• Scale is a "corresponding distance on land, connecting the two points represented by the same unit"
• For example, 1 cm on the map equals 1 km on the ground

Types of Maps

• Maps are classified into large scale and small scale
• Large scale maps Detail the geographical features in a small area
• Small scale maps depict only larger-area, important features

Differences Between Large and Small Scale Maps

• Large scale maps show a smaller area in greater detail
• Small scale maps show a larger area with less detail
• Large scale maps include Details of towns, cities, and villages
• Small scale maps show relief features like mountains, plateaus, countries, and continents
• Guide maps or topographical maps are large scale
• Wall maps or atlas maps are small scale
• Large scale has a scale of 1 cm = 50 m or 1 km
• Small scale has a scale of 1 cm = 100 cm

Types of Scales and Measuring Distance

• Scales can be measured by Verbal Scale, Representative Fraction (R.F.), and Linear Scale
• Verbal Scale expresses the scale in words (e.g., 1 cm represents 50 km)
• Representative Fraction (R.F.) shows the ratio between distances on the map and ground
• Linear Scale is a graphic scale representing the relationship between map and ground distances
• Distance is the space between two points, either long or short
• Distances can be measured in metric (cm, m, km)
• Usually distances are measured in a straight line

Calculating Distance

• Map distance is found using a scale
• Placing a divider helps measure distances
• For curved distances (roads, rivers), thread or paper strips can be used along the curve, then measured against the scale

Calculating Area

• Area is calculated by multiplying Length (L) × Breadth (B)
• Each grid square on topographical maps measures 2 cm x 2 cm, representing 4 sq cm
• The equivalent measure is 1 km x 1 km translating to 4 sq km on the ground

Conventional Signs and Symbols

• Conventional signs represent relief and human activities, essential for map reading,
• Symbols overcome space limitations, using letters, colors, or pictures
• Conventional signs offer a lot of information in a limited space
• These signs allow for simplified map drawing and reading
• Standardization ensures global understanding
• Symbols represent man-made and natural features like mountains, rivers and trees

Drainage, River and Irrigation Symbols

• A stream is represented by (nallah/nadi)
• Rivers are speckled if dry or arid, blue if perennial
• Canals are represented by a defined symbol
• Symbols represent dry rivers, rivers with islands/rocks, and disappearing streams in arid areas
• Seasonal streams appear only in rainy seasons
• Confluence is where the tributary meets the main river
• Meander indicates a bend in a river flowing through flat land
• Falls are marked with heights in hilly areas
• Broken ground indicates eroded land, often uncultivable
• Dendritic drainage patterns resemble leaf veins on flat lands
• Rectangular/Trellised patterns show streams joining at right angles, in areas of alternating rocks
• Radial patterns show streams flowing outward from a central point
• Disappearing streams, indicated by broken lines, dry up into the sand
• Symbols represent canals connected to rivers for irrigation or navigation
• Tanks are key for irrigation, storing water in rocky regions, embankments prevent flood
• Dry tanks are speckled, indicating seasonal rainfall

Wells, Water Bodies and Man-Made Features

• Tanks shown symbolises man-made bodies of water with an embankment
• Perennial lined wells, are symbolized as bores in the ground and lined with bricks and cement, they are shown as blue dots
• Unlined wells, which are kuchcha, show a blue circle if it contains water
• Depth is indicated in blue alongside
• Brackish lined wells, the water is too salty, and unfit for cultivation
• Tube wells are deeper bores which uses pumped water
• Springs are places where water surfaces
• Shoals are submerged rock areas
• Swamps are perennially flooded areas along coastal regions
• Dams control river overflow
• Weirs represents smaller dams
• Causeways are raised platforms or roads (not a bridge) where water is passable during dry seasons
• Islands are land surrounded by water
• Aqueducts are artificial channels conveying water
• Reservoirs are man-made tanks with an embankment

Transport, Communication and Road Symbols

• Metal roads are shown in red double lines and is a tarred road
• Milestone or kilometre stone numbers will indicate trade development
• Unmetalled roads are untarred roads indicating a village or an undeveloped region
• Pack-track (pagdandi) are broken lines made by animals or men
• Cart-tracks are paths made by bullock carts, it's slightly broader
• Footpath with a bridge, has a line of red dots where men temporarily cross a region

Railway and Settlement Symbols

• Broad gauge represents the distance between two train rails, measuring 1.69 m
• Metre gauge has a distance of 1 m between the rails
• Narrow gauge measures 0.7 m between the rails
• Permanent and temporary huts are represented
• A Deserted town is marked as deserted
• Nucleated settlements cluster together
• Linear settlements develop is a line of houses

Symbols for vegetation as well as natural and man-made structures

• Fort are displayed on the map
• Tower or Antiquities are displayed
• These include religious places like Mandir (Temple) and Church
• Vine, and Grass
• Open Scrub are marked
• Plantain for vegetation
• Conifers serve the cooler regions
• Bamboos found in a scanty rainfall
• Deciduous
• Surveyed tree are observed to represent a serve point in a certain black area
• Dense forest
• Open mixed juncle are both displayed and labelled
• Protected Forest is set as a shelter

Symbols for Height, Elevation and Relief

• Spot height measures the specific land height above sea level
• Triangulated height determines the height point
• Bench Mark serves as elevation marker engraved on ground
• Relative height measures the relative height or elevation
• Also included is the depth of water
• Contours are brown lines indicating positions Form lines display heights areas in broken contours
• Stony waste indicates rocky area
• Sheet rock indicates a presence

Quarry and Kiln Symbols

• Sand dunes: sand features shown in brown from desert region wind
• Stone quarry, indicating people and trade in the region
• Kiln (lime), showing the working people and trade

Place Symbols for understanding Maps

• Naka serves as outpost
• A Piao (drinking water access point)
• Viaduct displays roads and railways
• Shelving represents the slope reference to a river bank
• Dungar or hillock, embankment-A bank or round.
• Khera is a village
• Forest and rest stops
• Reserved Forests-Forests