Introduction to Scales
The area that is surveyed is large and vast. So it is necessary to bring the plans to some scale. The scale can be defined as the fixed ratio that every distance on the plan bears with the corresponding distance on the ground.
Representation of Scales
The scales can be represented in the following ways:
- Engineer's Scale
- Representative Fraction ( R.F)
- Graphical Scale
What is Engineer's Scale??
When on a map, one centimeter represents a whole number of meters on the ground, we call such scale to be an engineer's scale.
For example : 1cm = 10m
What is R.F?
When one unit in the plan represents some number of same units of length on the ground ie say as 1/1000 ..etc, the scale is represented as R.f or representative fraction. This ratio of the map distance to the corresponding ground distance is independent of the measurement units.
For a given engineer's scale, the R.F can be found very easily. For example if the scale is 1cm = 50m;
R.F = 1 / (50 x 100 ) = 1/5000;
These are also called as numerical scales.
What is Graphical Scale??
A graphical scale is a line subdivided into plan distance corresponding to convenient units of length on the ground.
Why are Scales always drawn on survey maps??
After many years, the numerical scale won't give accurate results if the paper or map shrinks. Graphical scale, if shrinks, will shrink proportionately. This makes distance determination of accurate than in the case of numerical scales.
- Scales used in Surveying Click Here>>
- Rules in Choosing a Scale for a MapClick Here>>
- Types of Scales in SurveyingClick Here>>
- Error due to the wrong Scale in SurveyingClick Here>>