A02 INTRODUCTION TO TOPOSHEETS -2

2. Toposheets 

 INTRODUCTION TO TOPOSHEETS -2

Hi, I'm Br. Hector. Sorry, I had not updated my geography blog for almost 10 years. Many students had been asking me to update my blog even though I don't teach the subject. Anyway, here I am. Do write your comments. I will be updating only if you find it useful. I hope you have gone through

INTRODUCTION TO TOPOSHEETS-1

I hope you have been able to understand. If not, go through that again and come back to this chapter. Let us continue.

Direction has been defined as an imaginary straight line on the map or the ground showing the angular position of various maps with respect to a common base direction. 

The line pointing to the north is regarded as the zero direction or base direction line. A map must have the base directions represented on it to enable the user to locate different features with respect to each other. North, south, east and west are the four major directions. These are also called cardinal points. In between cardinal points one may have several intermediate directions.A rough estimation of direction of the true north can be obtained by the Means of an ordinary watch. In the northern hemisphere if the watch is held in the horizontal position and turned until its hour hand points to the sun, the line that bisects the angle made by the hour hand with the line joining 12’O clock through the centre of the watch will point to the south. A similar exercise in the southern hemisphere will indicate the true north. This is also a crude method dependent upon the sun .

Question: What is the compass direction of Antroli (9576) from Sangla?
Check the map below.
See the arrow. Direction of  Santroli from Sangla is between North and East. So answer is North East. 
Remember the word "of" and " from". Don't get mixed up. "From" is the base. You are standing "from Sangla"  and  moving towards to Santroli.

Let's change the question.
Now you are in Santroli. You want to go back to Sangla. What is the direction?
Ofcourse, South West 

DISTANCE - TYPES

•Direct Distance

–Straight line (As the Crow Flies) distance

•Indirect Distance

–Along a path

•Road

•Cart Track

•River

•Canal

FINDING DIRECT DISTANCE

1.Measure the distance between the centre of the two places in cm

2.Convert distance in km (or meters)

  (Use the scale, i.e.; 2cm = 1 km)

3.  Round off to nearest 0.25 km (250 meters)

Calculation of Area

•Area= Length x Breadth
•In topo maps, each grid (square) 2cm X 2cm or 1 km to 1 km as per the scale 2 cm=1 km
•Therefore , area of each square is
4 sq cm (on the map)= 1 sq km (on the ground)
In metres, this can be expressed as
Area of each square (i.e. 4 sq cm) = 1000 X 1000
or 1,000,000 sq m.

To calculate the area by grid square method:

If there are some incomplete squares, area can be calculated as follows:
-Note the number of completed squares
-Squares covered half are taken as ½
-Squares covering less than half area are taken as 1/3
-Squares covering more than half of the area are taken as 2/3
-All these estimated squares are added together and the sum is multiplied by the scale of the area given out above to obtain the desired area.

Let's do it again! 

Representation of Relief on the Map and its Interpretation

•Earth’s surface – uneven – made up of hills, plains, plateaus, lowland which are varying in their elevation or heights from sea level.
•The total terrain is also called physical landscape.
•It can be represented on the maps through different methods, such as spot heights, contouring, etc.
•Surveying is considered a part of science of map making.
•Topographical maps are large-scale maps, they show a great deal of details about the relief.
•In Topographical survey, actual survey is carried out and different methods are used to represent relief on the map as follows.
i)  Hachuring
ii)  Hill shading
iii)  Form lines
iv)  Spot heights
v)   Triangulation points
vi)  Bench marks 

vii) contours
i)Hachuring: are short lines representing directions of a slope.
- For steep slopes , they are drawn closer together than for the gentle slopes.
- on flat grounds they can not be used at all.

DISADVANTAGE: it gives no indication of the actual height and that both high plateau region and low plain are unshaded
The close hachuring of the high mountain regions tends to obscure other details of the map.
II) HILL SHADING: A method of representing relief on a map by depicting the shadows that would be cast by high ground if light were shining from a certain direction.
It can be defined as the addition of shadows to give the optical illusion of a third dimension, making hills stand out in relief. The shadows can be regarded as those which would be cast on an imaginary relief model of the ground when illuminated by parallel rays of light from a selected direction or directions.
In this map, it is assumed to be from north west at an angle of 45 degree with the horizon.
This method too gives a general idea of relief of the country by it does not give the actual height and that it is difficult to know whether a piece of land is sloping uphill or downhill.

WHAT ARE RELIEF FEATURES?

•Major

–Mountains

–Hills

–Ridges

–Rivers

–Plains

•Minor

–Broken Ground

–Sand Dunes

Rock Outcrops

Man-made and Natural Features

Toposheets shows various details of an area- natural and man made features by means of conventional signs(legends), contours and pictorial diagrams in conventional colours.

Natural features – rivers, streams, sand features, trees, broken grounds, natural ponds, unlined wells, jungles, depresions (Dep), islands (in the exposed river beds), physical features like hills, waterfalls, spurs, river valleys and cliffs, shown by contours and their heights.

MAN made features – surveyed trees, queries, permanent huts, causeways, mines, metalled and unmetalled roads, pack tracts, cart tracts, artificial lakes with embankments, boundaries (national and international), post offices, police chowkies and inspection bungalows.

THE DRAINAGE

 The term drainage basin describes an area drained collectively by the network of a river along with its tributaries and sub-tributaries of various dimensions.

An area drained by a single river is called its Catchment Area. 

A drainage system as seen in the topographical sheets usually develops a pattern which is related to the general structure of its basin.

The entire river system including

–Tributaries

–Main river

–Distributaries

•Has a specific spatial arrangement

What is drainage pattern?

•The pattern that emerges due to the spatial arrangement of different components of the river system

–Tributaries

–Main river

- Distributaries

In ICSE, you need to concentrate on 4 drainage patterns.

3 distinct patterns can be recognized

1)Dendritic:

Dendritic drainage patterns are most common. They develop on a land surface where the underlying rock is of uniform resistance to erosion.
•Dendritic drainage systems are the most common form of drainage system. The term dendritic comes from the Greek word "dendron", meaning tree, due to the resemblance of the system to a tree.
•In a dendritic system there is one main river (like the trunk of a tree), which was joined and formed by many smaller tributary rivers. They develop where the river channel follows the slope of the terrain.
•Dendritic systems form in V-shaped valleys; as a result, the rock types must be impervious and non-porous

2. TRELLIS

Rectangular drainage patterns develop where linear zones of weakness, such as joints or faults cause the streams to cut down along the weak areas in the rock.

Trellis systems form in areas of alternating geology, particularly chalk and clay. The main river (the consequent) flows straight down hill.
Subsequent streams develop perpendicular to the consequent along softer rock and erode it away, forming vales.•The consequent river then cuts through the escarpments of harder rock.•Obsequent streams flow down the dip slope of the escarpments to join the subsequent streams.

3. RADIAL

•Radial drainage patterns develop surrounding areas of high topography where elevation drops from a central high area to surrounding low areas.

DIRECTIONS

•Directions- important tool while reading topo map.

•Directions are important for physical as well as urban features.

•Physical features- directions of rivers, streams,

•Urban cities from one another

DIRECTION-TO RIVER AND RIVER BANKS

•Need to know which direction river flows.

•REMEMBER THESE STEPS:

1.First look at the spot heights to determine the slope of the land

2.To know which side/bank of the river a place is situated, one has to locate the source of the river. Having located the direction of the river, imagine yourself standing at the source of the river facing the main river facing the main river. Now to your right is right bank and to your left is the left bank.

SIGNIFICANCE OF COLOURS IN TOPOSHEETS

Topo maps are not in black and white.

Various colours are used to show certain features. Each colour used on a map has significance.

1. BLACK – All names, river banks, broken ground, dry streams, surveyed trees, heights and their numbering, railway lines, telephone and telegraph lines, lines of latitude and longitude.

2. BLUE – Water features or water bodies that contain water.

3. GREEN – All wooded and forested areas, orchards, scattered trees and scrubs.

Note:- Prominent surveyed trees are shown in black. Surveyed trees have numbers on their trunks. They serve as landmarks and are not allowed to be cut.

4. YELLOW – All cultivated areas are shown with a yellow wash.

5. WHITE PATCHES – Uncultivable land

6. BROWN – Contour lines, their numbering, form lines, and sand features such as sand hills and dunes.

7. RED – Grid lines (eastings and northhings) and their numbering, roads, cart tracks, settlements, huts and buildings.

LAND USE

It includes the use of land under different categories  like : ° Natural vegetation and forest (which part of the area is forested, whether it is dense forest or thin, and the categories of forest found there like Reserved, Protected, Classified / Unclassified).

° Agricultural, orchard, wasteland, industrial, etc. ° Facilities and Services such as schools, colleges, hospitals, parks, airports, electric substations, etc.

In topo map location of vegetation is closely related to relief.

•In the highlands, vegetation is shown –green colour along with contours in brown showing elevation.

•To show density of wooded area, different terms used:

•Dense forest, open-mixed forest, open jungle, fairly-mixed jungle, dense-mixed jungle, mixed jungle, Reserved Forest (RF), Protected Forest (PF), fairly mixed jungle with bamboo, dense mixed jungle with bamboo.

•The exterior boundaries of areas of Reserved or Protected forest are shown by green ribands .

THE PLAINS:-

•Plains-mainly agriculture- cultivable land is shown in yellow colour

•White patch in plain shows bad land or rocky, uncultivable land.

•In such land, following features are found

Open scrub – scrub land where mostly sheep and goat rearing is practiced

•Stony waste – the land which is mostly covered with rock boulders and stones and cultivation is not possible.

SHEET ROCKS:-

•Sheet rocks – a region mostly covered with a sheet of rock.

•Rock outcrop – In such region subsoil is exposed and cultivation is not possible.

•Broken ground – developed because of absence of natural vegetation on both the banks of the river. It is common in the desert area and in the areas of gully erosion.This is formed due to floods which occur during rainy season. Because of floods, the top soil is washed away developing into bad land which has loose soil and is uncultivable.

LOW LANDS:-

•Plains which are situated at lower level are mostly characterized by a meandering river.

•A disappearing stream shows a desert or limestone area

•Presence of canal, wells, tube wells and tanks indicate use of land for agriculture by means of irrigation

•A meandering river shows a flat area

•Perennial lined wells indicate a higher water table and are shown by blue dots.

•Presence of dry streams, dry ponds, exposed river beds and broken land shown in black indicate an area with scanty rainfall or seasonal rainfall or a desert region.

•Settlements are generally found on either side of river-wherever irrigation by canals or perennial lined wells is available

SETTLEMENTS

 Settlements are studied under the following heads : 

° Rural Settlements: The types and patterns of rural settlements, i.e. compact, semi-compact, dispersed, linear, etc. 

° Urban Settlements: Type of urban settlements  and their functions, i.e. capital cities, administrative towns, religious towns, port towns, hill stations, etc

1. On a Topo map, all settlements are shown by symbols in RED colour.

2. The size of the symbol and size and style of letters used give an idea of the size of the settlement.

3. In the case of large cities, major roads are marked and named.

4. Deserted village cities, temporarily occupied huts are also shown.

5. Places of worship, forts, water towers, burial grounds, police stations, post office, dak bungalow, circuit houses, etc. are indicated by suitable symbols.

NOTE – Site is the land on which the settlement (village or town) is built.

Dense settlements : Fertile plains and wide river valleys.

· Sparse Settlements : forests, deserts, mountain slopes, plateaus and hill tops with poor vegetation·

Absence of Settlements: Swamps, marsh land, sandy deserts, thick impenetrable forests, flood-prone areas, steep mountain slopes.

OCCUPATION AND MAP FEATURES

The general occupation of the people of the area may be identified with the help of land use and the type of settlement. For example, in rural areas the main occupation of majority of the people is agriculture; in tribal regions, lumbering and primitive agriculture dominates and in coastal areas, fishing is practised. Similarly, in cities and towns, services and business appear to be the major occupations of the people.

AGRICULTURE – Level land with yellow wash; many wells

LUMBERING: Forests

CATTLE REARING – Pastures, meadows, grasslands, presence of road in highland region (sheep)

FISHING – Plenty of rivers

MINING –Stony wastes, quaries, limestone beds

TRADE – Dense settlements near road

INDUSTRY – Large settlements near roads and railways, presence of raw materials, (like making, cement industry near limestone beds)

TOURISM – hotels and inns

For ICSE students, you are to study the occupations in 45D/7 and 45D/10. Please study the symbols to interpret the occupation of the people.

Occupations have to be inferred from toposheets as there are no symbols to show the occupations of people.
•Sometimes, certain names like ‘farms’, ‘orchards’ provide some evidence of these occupations.

•The following list gives you some information about occupation of the people from a topo-sheet.

 The general occupation of the people of the area may be identified with the help of land use and the type of settlement. For example, in rural areas the main occupation of majority of the people is agriculture; in tribal regions, lumbering and primitive agriculture dominates and in coastal areas, fishing is practised. Similarly, in cities and towns, services and business appear to be the major occupations of the people.

OCCUPATIONS EVIDENCES
Forestry- lumbering, Forest or Green Patch
Agriculture- Yellow Patch or orchards with many wells
Cattle-grazing or sheep rearing, Meadows or Scrub, grasslands, meadows, pastures
Quarrying and mining -Mines and Quarries, lime stone beds
Trade Settlement near main roads, ports, rivers, etc – dense settlement

Entertainment & Cultural development -Golf Courses, Parks, Rifle Ranges, etc
Industry -Factory, mines, large settlements near roads and

railways, presence of raw materials (lime making and

cement industry near limestone beds)
Fishery- Coast,lakes, rivers, etc
Tourism- Hotels and Inns

•Thus, the occupation of the people of an area can be inferred from the following :
•Topography of land
•Size of settlement
•Presence of quarry and mines
•Communication network indicating trade

CLIMATE AND VEGITATION

MEANS OF IRRIGATION

 Irrigation largely depends on relief and land use pattern of area (blue)

•Hilly region- no cultivation is possible, hence there is no need for irrigation
•On the flat lands which are coloured yellow, one can see blue, round spots which represent perennial lined wells. – therefore one can say that the main source of irrigation in such areas are wells and the occupation of people is farming.
•Other means of irrigation are canals, ponds, artifical lakes with embankments and river in case it is perennial.
•Presence of dry streams and dry ponds with uncultivable lands shown in white indicates that the rainfall in the area is scanty.
•Presence of artificial man-made lake with embankment shows that water is being stored in off season and is used for irrigation through canals.

Means of Transport in Relation to Relief

•Transport always depend on the type of relief and drainage

Eg. Very high altitudes, mountaineous areas-only roads 

and no railway tracks- difficult to build at such heights

•On the map-roads are shown by means of symbols of cart tracks, pack tracts, metalled roads, unmetalled roads, footpaths with a bridge.

•Main towns- well connected by metalled roads show economic devp of the area-is the indication of trade being carried on.

•Hence town shows well developed.

•Causeways are raised platforms across a dry stream.

•During dry season when the stream dries up, people make a habit of crossing it.

•Thus, a footway is formed.

•Presence of many causeways shows that the area gets seasonal or scanty rainfall.

MODES OF TRANSPORT

HEIGHTS

APPROXIMATE OR RELATIVE HEIGHT-is height is not taken from sea level but with respect to the surrounding area. It may be the height of a dam, bridge, sand dune or it can be the depth of a well, tank, hill or river canal, for example , 3r, 5r, 8r, etc.

EXAMPLE: 3r - the relative depth of perennial lined well in 3 metres

●5r – the relative height of dry tank is 5 metres

NOTE: CHECK THE SYMBOL – if it is tank, dam, bridge, embankment, etc then write the answer this way - the relative height of .............................. is ................meters.

Let's do the conventional signs again

HOME WORK 

Identify the symbol!

A2 TOPOGRAPHICAL SURVEY MAPS=part 1

A4 INTERPRETING TOPOSHEETS PART 2

A3 SIGNIFICANCE OF COLORS IN TOPOSHEETS

A3A-IMPORTANT DEFINITIONS ON TOPOSHEETS

A1INTRODUCTION TO TOPOSHEETS-45D/7 AND 45D/10

A7 TOPOSHEET - EXERCISE 1

A5 TOPOSHEET - EXERCISE 2

A8 TOPOSHEETS - EXERCISE 3

A9 TOPOSHEETS - EXERCISE 4

ANSWERS FOR THE TOPOSHEET TEST

A6 SOME COMMON QUESTIONSON TOPOSHEETS. 

A6A-more explanation on toposheet

A6B-TOPOSHEET EXPLAINED

ATTENTION - SHALL WE REVISE TOPOSHEETS?

B1 Tired of practising toposheets???? No????? try this one -EXERCISE 5

B2 EXERCISE 6- toposheet for practice- have fun

B3 PRACTICE TOPOSHEET -1

B4-Why dont you try to answer these ?

B5-LET US SEE THE ANSWERS

B6-CHECK THIS TOPOSHEET