Friday, June 19, 2009

A3 TOPOGRAPHICAL SURVEY MAPS=part 1

A2

Fundamentals of Maps
THE SPHERICAL earth is best represented bya three-dimensional model of the earth, called a globe. All parts of the earth can be shown on it in their true shape, area and location along with correct cardinal directions and distances. But it cannot be made large enough to include detailed surface features. Hence, maps are much more useful tool than globes.
A map is a two-dimensional diagrammatic representation of the whole or part of the earth and its surface features both natural and cultural at a given scale on a flat surface. However, all that is shown on the map is not drawn to scale. Only distances and areas are drawn to scale. We are familiar with the maps of the earth surface. But it is possible to draw maps of other planets and even the sky when pertinent data becomes available to us. We already have crude maps of the Mars and the Moon. A map gives a picture of one or several of the elements of the earth’s surface and being creation of humans, it gives only those details, which its maker intends to give. Instead of showing the details in their true or visible shape and size, it uses symbols that may or may not have similarities with the shape and size of objects represented. Maps have unique advantage of showing objects or patterns that may be intangible or invisible.For example, it may show political boundaries or rainfall pattern or crop distribution, which may not be marked on the ground. Thus, maps are basically symbolic drawing of visible as well as conceived locational and distributional patterns of whole or a part of the earth, the sky or any other heavenly body.
There are various ways by which the earth can be mapped:
(a) by freehand sketches and diagrams;
(b) by actual survey with the help of instruments like chain and tape, plane table, prismatic compass and theodolite etc.;
(c) by photographs (ground photographs/aerial photographs);
(d) by satellite and radar charts.With the availability of high-speed computers and Global Positioning System(GPS), digital mapping has emerged as an important tool of mapping.

The amount of information given in a map depends on:
• Scale;
• Projection;
• Conventional signs and symbols;
• Skill of the cartographer;
• Method of map making; and
• Requirement of the user.


Types of Maps
Maps are of different types. Each map is unique in its design, content and construction and hence, a type by itself.
Maps are broadly classified on two bases: scale and purpose or content .
Based on the scale, there are two broad categories of maps:
i. Large Scale; and ii. Small Scale
i. Large Scale : These maps represent small area of the earth on a large size of paper/cloth/plastic sheet with greater details. Examples of some of the large scale maps are:
(i) Cadastral Maps: The term cadastral is derived from French word cadastre’ meaning register of territorial property.The Cadastral maps are drawn to register the ownership of landed property by demarcating the boundaries of fields, buildings, etc. They are especially prepared by governments to realise land revenue and property taxes. The village maps of our country may be cited as an example of large scale maps. These maps are drawn on a verylarge scale, varying from 16 cm to a km to 32 cm to a km so as to fill in all possible details. The city maps may also be included in this category.

(ii) Topographical Maps: These maps are also prepared on a fairly large scale. They are based on precise surveys conducted by the Survey of India, Dehradun. They show general surface features in detail both natural and cultural. Principal topographic features depicted on these maps are relief, drainage, swamps and lakes, forests, villages, towns, means of transport and communication like roads and railways, and canals. Indian toposheets are generally prepared on the scale of 1:50,000.
Small Scale : These maps represent large areas on a small sheet of paper. They have fewer details. Examples of small scale maps are Atlas and Wall maps. The maps included in this book are also small scale maps. They give only a general picture of the area represented.
(i) Wall Maps: These maps are generally drawn boldly so that they can be seen from a distance. They are used in classrooms and cater to a larger audience. These maps broadly show very large areas like world as a whole, hemispheres, continents, and countries, states and districts. The scale is smaller than that of topographical maps but larger than atlas maps.
(ii) Chorographical or Atlas Maps: The Atlas maps are drawn on a very small scale and give a highly generalised picture of the natural and cultural aspects such as the physical, climatic and economic conditions of different regions of the earth. Only a few atlases are prepared on a 1:1,000,000 scale like the ‘Times Atlas of the World’. The Registrar General of India brings out Census Atlas from time to time. National Atlas and Thematic Mapping Organisation (NATMO) is a well-known important organisation in our country that publishes all kinds of maps for various purposes depicting different parts of the country. Thematic maps are usually prepared on small scale highlighting specific themes such as relief, temperature, and political divisions.
According to purpose or theme, maps could be broadly categorised as follow :
(a) Physical or Natural Maps:-
(i) Orographic or relief maps represent features like mountains, plains, plateaus, drainage patterns, etc.
(ii) Bathymetric maps show the depth of the oceans and seas. They are also known as charts.
(iii) Geological maps represent rocks that form the crust of the earth, and their mode of occurrence and disposition.
(iv) Climate maps show average condition of temperature, pressure wind andprecipitation of the world or part of it over a long period of time.
(v) Natural vegetation maps show natural flora of an area or region.
(vi) Soil map exhibits various types of soils covering the area.
(vii) Weather maps denote the average condition of temperature, pressure, wind and precipitation over a short period, which may range from a day to a season.
(viii) Astronomical maps show the position of stars and planets in the sky.
(b) Cultural Maps:-These maps show the man-made features or human aspects.
(i) Economic maps show distribution of important minerals, agricultural andindustrial products, and lines of transport and communication. They help inassessing economic development and potential of the area covered by the map.
(ii) Political maps show boundaries between different countries and states within countries.
(iii) Historical maps show the past events and facts.
(iv) Social maps depict elements like language, caste, ethnic groups and religion.
(v) Land utilisation maps exhibit the character of land use.
(c) Military Maps: Maps used by Defence Services are called Military maps.
(i) General maps on a scale of 1:1,000,000 or more depict only the broad topographical features. They are used by the Defence Services for general planning purposes.
(ii) Maps having scales ranging from 1:1,000,000 to 1:500,000 are oftenclassified as strategic maps. These maps are used for planning concentratedmilitary action.
(iii) Maps with a scale of 1:500,000 or less are called tactical maps. They serve as guides to small units like battalions and patrol units prior to and during movements anywhere near the front line.
(iv) Photomap is an air photograph with strategic and tactical data superimposed on it.All maps have some common elements. Location and distribution of various features and phenomena are depicted using distance, direction, and conventional signs and symbols.
SCALE
Scale is the relationship between the distance on a map and the real distance on the earth’s surface.
It may be expressed as a representative fraction (ratio), a line scale or a statement scale. It is an important element of a map because it gives relative picture of the ground reality. As you have read earlier, maps are generally classified into large scale and small scale. However, there is no universally accepted standard for classifying maps according to scale. What one considers to be large, may appear to be small or medium for others. The same person may consider a map to be of large scale for one purpose but of small scale for another purpose. As a result of this each specialised group of map users sets up its own standards for classification.As a matter of convention, maps having a scale 1:50,000 upto are classified as large scale maps, those falling between 1:50,000 and 1:1,000,000 as medium scale maps and those having scales above 1:1,000,000 are treated as small scale maps. The million sheets of the Survey of India and the National Atlas of India are considered to be medium scale maps.
Methods of Expressing Scales


The scales can be expressed in three ways:
1. Statement: The scale may be indicated in the form of a written statement. For example 1cm on the map represents 1 km on the ground. The scale is written as 1 cm to 1 km. This means that 1 cm on the map corresponds to 1 km on the ground. Although it is simple to express in words, it is difficult for those who are not familiar with the unit of measurement used. Besides, the scale will not be the same when the original map is reduced or enlarged. As such, this method is not very useful.
2. Representative Fraction (R.F.): It is also called as numerical scale. It is expressed as a ratio of map distance and ground distance. For example 1:1,000,000 means one unit of distance on the map corresponds to 1,000,000 units of distance on the ground. The advantage of R.F. is that it can be used universally irrespective of the local unit of measurement of distance. The mapcan be reduced or enlarged without changing the R.F.
3. Linear Scale or Graphical Scale: This scale is expressed as a horizontal or straight line. The base is calibrated to express visual equivalents of representative fraction or verbal scale. The bases are divided into a number of equal parts and are marked to show what these divisions represent on actual ground. The scale has the advantage that it remains true even after reduction or enlargement of the map. However, it is useful only to those who are familiar with the particular unit of measurement.
Distances on the map are smaller than the corresponding distances on actual ground. Scale is the means which enables us to reduce the whole or a part of the earth to a size which is not only convenient and handy but also logical and scientific. A general definition of scale is that it is a ratio between the distance on a map and the corresponding distance on the earth. For example if two points located 10 km apart are shown 1 cm apart on a map, then the scale of the map would be 1 cm to 10 km. It may also be converted into R.F as given below.Suppose, 1 cm = 10 KM.

MAP DISTANCE
_______________
GROUND DISTANCE
=
1 cm
_____
10 km
=
1 cm
____________
10 X 10,000 cm
= 1: 1,000,000
(Note: 1 km has 100,000 cm.)

Methods of Measuring Linear Distance
Linear distance on maps are of two types:
(i) Straight lines like roads, railway line, and canals;
(ii) Curved or Zigzag lines, showing streams, coastline etc.
(a) When the line is straight, the distance can be measured with the help of a divider.Open a pair of dividers and place one of its legs at one end of the straight distance and the other leg on the other end on the map. Then lift the divider and place it on the calibrated bar scale to get the distance on the ground.
(b) When the route is zigzag, place one end of a thread at the starting point and carry the thread along the line. After completing the distance stretch the thread and measure the length. It will give approximate distance.It can also be measured with the help of a plain divider, as explained earlier, but the measurement will be less accurate. It can also be done with the help of a strip of paper.
(c) Rotameter is an instrument having a route measuring wheel. Distance between two points is measured by allowing the wheel of the rotameter to move along the route.
Direction
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 similarexercise in the southern hemisphere will indicate the true north. This is also a crude method dependent upon the sun .
Legends
Every map contains a legend or a key. It lists the features and the signs or symbols used in the map for showing these features. As you know various types of features or phenomena are represented on maps. They relate to both land and sea and are shown with the help of conventional signs and symbols. The signs and symbols include lines, icons, alphabets, shadings and colours. As a convention, specific colours show certain area features.
Review Questions
1. Answer the following questions:
(i) What is a map? What are its advantages?
(ii) What is a scale? What purpose does it serve on a map?
(iii) What are the small scale maps? Give two examples of small scale maps.
(iv) What is a cadastral map?
(v) What are cardinal points?
2. Write short notes on:(i) Wall maps (ii) Linear Scale (iii) Base direction line.
3. In how many ways the earth can be mapped and what factors determine the amount of information given in a map? Discuss.
4. Describe various types of maps and their uses.
5. What are the different ways of expressing scale? Explain the merits and limitations of each method giving suitable examples.
6. What is R.F.?
REMEMEBR 7 STAGES


Stage 1: introduction to types of maps;
• Stage 2: interpreting the shape of the ground from a map;
• Stage 3: plotting grid references;
Stage 4: measuring distances
•Stage 5: orienting the map to the ground;
•Stage 6: using the Silva compass; and
•Stage 7: conventional symbols.
INTERPRETING SHAPE OF THE GROUND FROM A MAP

When planning a route or looking for good positions for observation or fire, you must be able to look at the map and get a good mental picture of the ground.

STAGE 1 – TYPES OF MAPS
There are different types of maps. We will focus now on Topographical Maps.
1. Topographical maps
In order to do this, you must be able to:a.Interpret the shape of the ground from a map;
b.Definition of relief; and
c.Representation of height.


CONTOURS

A contour is a line on a map joining two points of equal height, and is the standard method of showing relief on a topographical map.
Contours are shown at regular vertical intervals.
  • On a 1:50,000 map the interval is 10 m.

INTERPRETATION OF CONTOURS

The shape of the contours indicates the shape of the ground.
When contours are further apart, the slope is gentle and when contours are close together the greater the drop.
When contours are equal distance apart the slope is uniform:
a.Contours are continuous. No matter how far they travel, they always return to where they started. Except for a cliff.
b.When spacing of contours down a slope gets close together at the bottom, the slope is convex.

c. When spacing is further apart, the slope is concave.


STAGE 3 – PLOTTING GRID REFERENCES

•A grid is a rectangular square system of lines superimposed on a map, within which any point can be located.
Maps are normally printed so that north is on top.
•North / South lines are called Eastings because the numbers increase as they go East.

•East / West lines are called Northings because the numbers increase as they go North.

What are the 3 points in determining height?
1.bench marks;
2.trig points; and
3.spot height.


What are Eastings and Northings?

1.Eastings run – move left to right; and
2.Northings run – bottom to top.

What are the two most important things to remember when giving a grid?
1.Easting value first; and
2.never round up.

What is the purpose of a contour line?

Joins points of equal heights.

A topographic map is a type of map characterized by large-scale detail and quantitative representation of relief, usually using contour lines in modern mapping, but historically using a variety of methods. Traditional definitions require a topographic map to show both natural and man-made features .

The Centre for Topographic Information provides this definition of a topographic map:"A topographic map is a detailed and accurate graphic representation of cultural and natural features on the ground."
According to Cartographer's Kraak and Ormeling,"Traditionally, the main division of maps is into topographic and thematic maps. Topographic maps supply a general image of the earth's surface: roads, rivers, buildings, often the nature of the vegetation, the relief and the names of the various mapped objects."
•The study or discipline of topography, while interested in relief, is actually a much broader field of study which takes into account all natural and man made features of terrain.

Uses

•Topographic maps have multiple uses in the present day: any type of geographic planning or large-scale architecture; earth sciences and many other geographic disciplines; mining and other earth-based endeavours; and recreational uses such as hiking or, in particular, orienteering, which uses highly detailed maps in its standard requirements.


Map conventions
The various features shown on the map are represented by conventional signs or symbols. For example, colors can be used to indicate a classification of roads. These signs are usually explained in the margin of the map, or on a separately published characteristic sheet]
•Topographic maps are also commonly called contour maps or topo maps. In the United States, where the primary national series is organized by a strict 7.5 minute grid, they are often called topo quads or quadrangles.
•Topographic maps conventionally show
topography, or land contours, by means of contour lines. Contour lines are curves that connect contiguous points of the same altitude (isohypse). In other words, every point on the marked line of 100 m elevation is 100 m above mean sea level.

There are several rules to note when viewing topographic maps:
The rule of V's: sharp-pointed vees usually are in stream valleys, with the drainage channel passing through the point of the vee, with the vee pointing upstream. This is a consequence of
erosion.

The rule of O's: closed loops are normally uphill on the inside and downhill on the outside, and the innermost loop is the highest area. If a loop instead represents a depression, some maps note this by short lines radiating from the inside of the loop, called "hachures".
Spacing of contours: close contours indicate a steep slope; distant contours a shallow slope. Two or more contour lines merging indicates a cliff.
•Of course, to determine differences in elevation between two points, the contour interval, or distance in altitude between two adjacent contour lines, must be known, and this is given at the bottom of the map.
•These maps usually show not only the contours, but also any significant
streams or other bodies of water, forest cover, built-up areas or individual buildings (depending on scale), and other features and points of interest.
•Today, topographic maps are prepared using
photogrammetric interpretation of aerial photography. Older topographic maps were prepared using traditional surveying instruments.
•In most cases, contour intervals are consistent throughout a map. Sometimes dashed contour lines are present; these represent half the noted contour interval.

Understanding Topographical Maps

Understanding of surface depends on the ability to interpret topo maps. They-
Are based on accurate surveys.
•Show a variety of landforms with carefully chosen symbols & signs.
•Shows natural features like hills, valleys, waterfalls,
•Also show man made features like roads, railways, buildings, bridges and canals.
TOPOSHEETS ARE:-
Are prepared on a number of sheets since they are large scale maps.
•Each sheet gives the details of a part of the whole area.
•When these joined together, they form a map of the whole area.
INTERPRETATION OF TOPO MAPS AND SURVEY MAPS

IT involves ability to follow the symbols portrayed in the map.
•Understand the information given in pictorial and written form
•Visualize the topography of the original area by interpreting the contour
•Spot heights skillfully
•Map reading is a practical skill.
•Can be developed only by reading topo map very minutely and mentally analyzing the details with the help of conventional signs & symbols given in their conventional colours'
•As the conventional symbols cannot cover all the graphical details, each topographical map sheet provides the necessary information in the margin for the users.
1.Identification of topographical maps
2.Reading the Grid reference
3.Scale (R.F.)
4.Representation of Relief by contours
5.Directions
6.Measuring distances and calculating distances
7.Drainage
8.Man-made and natural features
9.Means of transport in relation to relief
10.Land use and irrigation
11.Settlements
12. Inferring occupations
13. Importance of colours and tints in topographical survey sheets
14. Legend
15. Glossary of conventional signs and symbols used in survey maps

INFORMATION IN THE MARGINS
i)The number of the topo sheets: Topo sheets numbers can give an idea as to which part of India is shown on the map. For example, topo sheet numbers 45D/7, 45D/10 and 45 F/3 show parts of Gujarat and Rajashthan.





Knowing the number of toposheet can give us a clue about the general physical relief of the region and its climate which can be confirmed by other information given in the map.

•Eg- since all toposheets are from India, it may be inferred that all the reigons represented by those topo sheets would have a tropical monsoon climate, with seasonal rainfall.
•Western Rajasthan – u may expect scanty rainfall- a fact which could be verified by the presence of dry river beds and disappearing streams.










•45D/7 shows a region of northern Guj, closer to the border of Rajasthan
•45D/10 lies in the southern part of Rajasthan close to the border of Gujarat region
•45F/3 lies in the western Rajasthan, near Jodhpur
•53B/7 shows a region in Punjab, close to the border of Haryana.
•56D/11 shows a region in north-east Karnataka.
•64P/13 shows a region in north-east Orissa.
ii) Latitudinal and Longitudinal extent: These indicate in whichpart of the Earth the area is located.
•On a 4 degree topographical map, at least 4 lines of latitude and longitude can be seen. But as the scale of the topo map increases, the number of latitudes seen on the map decreases.



GRID REFERENCE


•A Grid is a set of lines used to find the exact location of places on a map.
•The National Grid Reference is a system of rectangular co-ordinate.
•The origin of the grid reference lies at a point in the south-west corner of the map.
•Thus any place on the map can be located by starting its distance east or north of the origin of the grid reference.
•Topo maps bear the national grid of squares drawn to the scale of 2 cm=1km with each square having a side measuring 1 km.
•These are sheets most commonly used for various purposes and are of vital practical importance.
•Vertical lines=Eastings since they are numbered from west to East
•Horizontal lines = Northings - they are numbered from South to North
•Net work of horizontal and vertical lines or the Eastings and Northings , is called the Grid.
READING THE GRID REFERENCE


i)Origin is the South –West (SW) corner of the map. The reading on the map is always taken with reference to this origin.
ii)Eastings are always read to the East of the origin.
iii)Northings are always read to the North of the origin.
•It is also identified as the Grid Reference















i)The readings are always taken to the right of the Eastings and to the North of the Northings.
ii)While giving a grid reference, Eastings are always stated first, followed by Northings


Grid Reference of this picture is 2676










Four Figure Grid Reference:-•In four-figure grid reference, the first two figures are the eastings and the last two are the northings.

Six Figure Grid Reference:•For greater accuracy, a third figure may be added to two-figure eastings and northings.
i) Obtain the four figure reference by using first two digits of eastings and northings.
ii)Then divide each kilometre into ten parts visually, both vertically & horizontally.
iii) Mark the division of eastings and the division of the northing corresponding to the location.
iv) The crossing point is the location of the reference point.
SCALE
•Refer to Survey Map No. 45D/7
•In the map, 1:50,000 is the R.F. of the map, which means that one unit on the map represents 50,000 units on the ground.
•For example, 1 cm on the map represents 50,000 cm on the ground.

(Scale of this toposheet is)
Scale-2cm:1 km or1:50,000


R.F. or Representative Fraction is the ratio between the distance on the map and the corresponding distance on the ground in the same unit.•Therefore, R.F.
Distance on the map
____________________________
Distance on the ground

In the above map, R.F. = 1:50,000
This map is referred to as 1:50,000map and its scale is 2 cm=1km.
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 markscontours

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.

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.

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.




SIGNIFICANCE OF COLOURS IN TOPOSHEETS
On toposheets 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.
SETTLEMENTS
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
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
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.

















15 comments:

Unknown said...

this online tutorial has helped me a lot in understanding the particular lesson well...thanksss a lot for ur help !!!

Unknown said...

Dear sir

The content is very usefull, it is not serving my Daughters Purpose Because she is studying in VIIIth Stantard in Bishop Cotton Girls School in Bangalore

Any how I thank for your effort in helping the student community

Regards

N.A.VENKATESH GUPTA

Unknown said...

this online revision has helped me a lot especially for last min revision.
i dont take geogo tuts & i had many doubts but all were cleared when i saw this.........
thanxxxxxxxx a lot........... may your tribe increase.

rohan.

Michael Butters said...

While most people think of land surveys in the most basic sense, the drawing of the boundaries of a property, in actuality there are many varied and different ways of surveying that service many different industries.

Topographic Surveys

Michael Butters said...

Topography is generally known as the study of earths surface, and its features and shape. It also gives the description of the features (such as surface, shapes, vegetation cover & elevations), depicted in maps which are called "TOPO.

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Sweta said...

Thank you sir!!
Helped a lot during revision!!
Sweta, Shillong

victor deepak said...

Great Effort!!
Anyone knows where to buy survey maps in mumbai? I did them during my ICSE almost 20 years ago. Always loved them.
Thanks.

Unknown said...

Sir I have a doubt.
If in BOARD exam they ask to find the 6 figure grid reference of a settlement so we take the centre point or the starting point of the settlements ?
My teachers have all given different answers for the same.
Kindly give your advice.
Regards,

Unknown said...

Respected sir this content is very precise and conceptual. I find it to be extreamly useful to all those who have some work with toposheet maps and basic understanding of maps. I thank you for your help.







shanti prasad

Unknown said...

The total information is so understandable way for all, but one thing that add some more information about how the SOI giving the numbers to toposheet ( like 45O/4..) with explonation...

Unknown said...

Awsome sir hats off to u very easy to understand :)

GPSURYA said...

Nice work sir....

genesislandsurevy said...

Thanks for sharing such a useful information with us. We have also crafted some information on the topographic survey.

Priya anto said...

Thanku so much sir

Unknown said...

can we consider Surveyed tree as a man made feature?