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PART A: SCALE CONVERSION:
Before we begin conversion of scale you have to acquire the basic knowledge of scale.
Scale is the ratio between map distance and the ground distance.
Scales are of the three types as indicated below:
(i) Small Scale e.g.: 1:1000000
(ii) Medium Scale e.g.: 1:50000
(iii) Large scale e.g. 1:200
Maps of regions, countries, world, continents are drawn using small scale, so the larger the area the smaller the scale and vice versa.
WAYS OF EXPRESSING A SCALE
(I) Representative fraction scale
(ii) Statement scale
(iii) Linear scale
(i) Representative Fraction scale (RF Scale)
This way is expressed in form of ratio or fraction such as 1:40000 or 2/100000
The numerator expresses map distance while the denominator expresses Ground distance.
That means that 1 unit on a map represents 50000 units on the grounds. Such a unit can be anything such as Centimetres, Metres, Feet etc.
(ii) Statement Scale or Verbal scale
This is given in form of a statement like 1cm represents 2 km, or 1 cm on a map represents 9 km on the ground or in short like 1cm to 11km
iii) Linear Scale or Graphic scale or bar scale
This is the way of presenting a scale in form of bar or graphics as shown below:
Convert 1:50000 into statement scale
(i) 1:50000 means 1cm to 50000cm
(ii) Convert 50000 cm into Kilometres
(iii) Simply divide 50000 by 100000 because 1km = 100000cm
Therefore 50000/100000 = 1/2
1 cm represents 1/2 Km
Convert 2:400000 into statement scale
(i) 2:400000 means 2cm to 400000cm
(ii) Convert 400000cm into Kilometres
(iii) Simply divide 400000 by 100000 because 1km = 100000 cm
Therefore 400000/ 100000 = 4
2 cm represents 4 Km
By dividing both sides by 2:
1cm to 2 km
The map has been drawn to a scale of 1cm to 3km, what is the scale in Representative Fraction (RF Scale)?
Given statement scale 1cm to 3km, this means that 1cm on a map represents 3km on the ground.
Convert 3km into cm as shown below:
Therefore: x = 300000cm
The distance from one town to another is 12cm on a map, if its actual distance is 6km, what is the RF scale of a map?
Given 12 cm and 6km
Converting 6km into cm we get 600000cm
Now we have 12cm and 600000cm
Put as ratio, 12:600000
Divide both sides by 12 in order to get 1 in the numerator.
Therefore the scale is 1:50000
*********** END OF PART ONE ************
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