IMPORTANT INFO TO HELP IN TOPO INTERPRETATION
SCALES
On 45D/10 and 45D/7 the RF scale is expressed as 1:50,000, meaning 1cm on
the map represents 50,000 cms on the ground.
EASTINGS
Are vertical lines with values increasing West to East.
NORTHINGS
Are horizontal lines with values increasing from South to North.
POINT OF ORIGIN
It is the South-Western most point of the grid network at the intersection of
one Easting and one Norhting.
Eastings are always mentioned before the Northings.
AREA
Area of one grid square is one square kilometre, since 2 cms on the map is
equivalent to 1 km on the ground. The area of any surface on the map is
calculated by counting the number of grids in a given area.
Count the number of complete squares contained within the area.
Squares including more than half of the area concerned are taken as 2/3
squares.
Squares including half of the area are taken as ½ square.
Squares with less than half the area of the grid are taken as 1/3 squares.
Add all the squares to get the total area of the concerned portion.
FORMLINES
Are brown lines in dashes – indicate uneven topography.
TRANSPORT AND COMMUNICATION
In 45D/7 and 45D/10 have the major means of transport as cart tracks,
metalled and unmetalled roads, railway lines.
Modes of transport – carts, trains, buses, etc.
Dominant means of transport is the one which is most widespread all over
the map extract and connects the maximum number of settlements.
Hilly areas show pack tracks and footpaths.
Large nucleated settlements may have metalled roads, railways, post-office,
telephone lines, etc.
DISTANCE
Use twine /thread to measure the distance in cms and convert it to kms and
metres with the aid of the map scale. In case of 45D/10 and 45D/7, the
statement scale is 2cm=1km.
REPRESENTATION OF DRAINAGE
A blue line given in a river stream indicates the river to be perennial. Black
dots given in the river indicate it is a dry river.
A perennial water body has a permanent supply of water throughout the
year. On the other hand, a seasonal or non-perennial water body dries up at
certain times of the year. Presence of seasonal rivers indicates the
occurrence of seasonal rainfall in that region.
DIRECTION OF FLOW OF A RIVER
Arrow is marked on the river bed.
If the arrow is not marked the decreasing value of the contours and spot
heights and pattern of crossing of contours on the river / stream , indicate
the general slope of land.
REPRESENTATION OF MEANS OF TRANSPORT AND COMMUNICATION
Cart tracks, metalled and unmetalled roads, railway lines, footpaths are the
major means of transport observed in 45D/7 and 45D/10.
Modes of transport are the vehicles which ply along different means of
transport, example carts, trains, buses, cars, etc.
Dominant means of transport is the one which is most widespread all over
the map extract and connects the maximum number of settlements.
All means of transport are means of communication too/ though all means of
communication may not be means of transport.
Means of transport and communication are interrelated to relief, landuse,
drainage and settlement of an area. For instance
Hilly areas show pack tracks and footpaths.
Large nucleated settlements may have metalled roads, railways, post office,
telephone lines, etc.
Presence of telephone lines indicates development.
Availability of transport and communication lines help in the coming up of
large settlements along the metalled roads and railways encouraging trade
and development.
Lack of transport and communication facilities indicates a poor stage of
development of the concerned area.
Level land will have roads and uneven land will have pack tracks and
footpaths.
Undulating land may have cart tracks commonly.
REPRESENTATION OF SETTLEMENTS
The importance of a settlement can be gauged from its size and the number
of civic facilities and amenities it offers.
The connectivity of the settlement to other settlements by transport and
communication also determines its significance.
The availability of water or a perennial source has always played an
important role in coming up of settlements.
Fertile land, scope of earning a livelihood, scope for trading, are other factors
that lead to settlements.
Representation of landuse / occupations
Cultivation – yellow wash indicates presence of cultivated land, fertile soil
and availability of water supply.
Forestry – Green wash indicates presence of natural vegetation. Phrases like
mixed jungle, fairly mixed jungle, dense jungle, open scrub and fairly dense
jungle with bamboo indicate the specific type of vegetation found in the
area.
Animal rearing – Presence of open scrub in an area with low shrubs and
bushes with grass is found where rainfall is scanty. This type of vegetation
can support the grazing of animals as an important land use.
Fishing – The presence of a large perennial water body like a tank which is
natural, a man-made reservoir or a perennial river encourages fishing.
Rock cutting / Quarrying – The presence of rock outcrop, a sheet rock, stony
wasteland printed on the map extract encourages rock-cutting/ quarrying.
Trading – Annual fair which is printed alongside certain settlements well
connected by transport lines like cart tracks and roads indicate the practise
of trading .
LANDUSE
Making of lime – where a lime quarry is located / lime kiln is located [ check
the symbol]
Making of bricks – where brick kiln is located [ check the symbol]
Making of salt – where there are perennial lined well with brackish water
INTERPRETATION OF CLIMATE
Areas covered by 45D/10 and 45D/7 belong to arid and semi-arid areas of
Gujarat and Rajasthan, so they have tropical, monsoonal climate.
High temperatures and low seasonal rainfall below 60cm, so the rivers and
tanks are non- perennial and most of the areas thus under scrub vegetation.
Wind erosion is more active , so sand dunes and depressions formed by
action of wind are commonly found.
Presence of sandy features and porous soil leads to the development of a
disappearing drainage pattern.
Tropical Monsoon climate is characterised by alternating wet and dry climatic
conditions with a distinctive dry period.
Presence of the following indicate seasonal rainfall –
A narrow perennial channel in a dry bed.
Seasonal streams
Seasonal canals/ natural and man-made tanks.
Cart tracks crossing streams
Transport lines indicated with ‘ MOTORABLE IN DRY SEASON ONLY’ printed
on the map.
Presence of broken ground along river banks – shown by irregular black lines
. The gully erosion of the river banks takes place due to flowing of water in
rainy season and lack of vegetation along the banks to hold the water.
Presence of causeways which are cemented paths or raised roads across a
seasonal stream bed which is used for crossing a stream. It saves the cost of
constructing a bridge.