of Geography

When considering ‘Cartography’ art and science of map-making, the Science bit is the skill and art is the craft. So it becomes quite important to learn the basics of map making i.e. the ‘science bit’.

Scale and projections are the two very basics to start with, both are discussed in conventional map making. The scale is the first step up the ladder but here we will discuss projections first as today we deal with projection much more but scales are equally important.

Projections

What are projections?

Why are they important?

Since map making is about the representation of what we see, we need a surface that is producible on a flat surface. To make it more clear geometrically it is impossible to represent a sphere on a flat surface without distortions.

When that shape is a 'Geoid' (that's what we call our Earth) with three-dimensional features the process becomes even more complicated and the only option we have is to make a compromise.

Therefore it becomes important to choose our compromises rightly. We should know the purpose of the map construction to preserve the right attributes and let go of others.

Scale

The scale is where the art and science combine as a map without a scale is just a sketch.

A Scale can be defined as the ratio between a distance on the drawn map to the actual distance on the ground.

If a simple ratio of 1:1000 is taken this would mean 1 unit on map will represent 1000 unit on the ground. This simple relationship between distances on the ground and on map is known as a scale.

This relationship can be expressed in three ways

(a) Statement of Scale (Verbal Scale)

(b) Representative Fraction (RF)

(c) Graphical Scale

Each of these methods has its benefits and drawbacks over others but usually, you will find more than one represented in combination on a map.


While interpreting these relationships we require a system of measurement. Its to be noted that RF (Representative Fraction) are just units and can be interpreted in any system of measurement.

Two system of measurements are

(a) English System of Measurement (i.e. Mile, Furlong, Yard, Foot, Inch)

(b) Metric System of Measurement ( i.e. Kilometre, Hectometre, Decametre, etc.)