Orders of Magnitude and Scale
Map Scale
Chapter 2
Map Scale
You have read in Chapter 1 that the scale is an essential element of all types of maps. It is so important that if a network of lines and polygons does not carry a scale, we call it a “sketch”. Why is the scale so important ? What does it mean ? What are the different methods of showing the scale on a map? How useful is the scale in measuring the distances and the area? These are some of the questions which will be taken up in the present chapter. Glossary
Denominator: The number below the line in a fraction. For example, in a fraction of 1 : 50,000, 50,000 is the denominator. Numerator: The number above the line in a fraction. For example, in a fraction of 1 : 50,000, 1 is the numerator. Representative Fraction: A method of scale of a map or plan expressed as a fraction showing the ratio between a unit distance on the map or plan, and the distance measured in the same units on the ground.
What is Scale ?
You must have seen maps with a scale bar indicating equal divisions, each marked with readings in kilometres or miles. These divisions are used to find out the ground distance on the map. In other words, a map scale provides the relationship between the map and the whole or a part of the earth’s surface shown on it. We can also express this relationship as a ratio of distances between two points on the map and the corresponding distance between the same two points on the ground.
17
Practical Work in Geography
There are at least three ways in which this relationship can be expressed. These are: 1. Statement of Scale 2. Representative Fraction (R. F.) 3. Graphical Scale Each of these methods of scale has advantages and limitations. But before taking up these issues, let us understand that the scale is normally expressed in one or the other system of measurement. You must have read and/or used kilometre, metre, centimetre etc. to measure the linear distances between two points on the ground. You might have also
Chapter 2
Map Scale
You have read in Chapter 1 that the scale is an essential element of all types of maps. It is so important that if a network of lines and polygons does not carry a scale, we call it a “sketch”. Why is the scale so important ? What does it mean ? What are the different methods of showing the scale on a map? How useful is the scale in measuring the distances and the area? These are some of the questions which will be taken up in the present chapter. Glossary
Denominator: The number below the line in a fraction. For example, in a fraction of 1 : 50,000, 50,000 is the denominator. Numerator: The number above the line in a fraction. For example, in a fraction of 1 : 50,000, 1 is the numerator. Representative Fraction: A method of scale of a map or plan expressed as a fraction showing the ratio between a unit distance on the map or plan, and the distance measured in the same units on the ground.
What is Scale ?
You must have seen maps with a scale bar indicating equal divisions, each marked with readings in kilometres or miles. These divisions are used to find out the ground distance on the map. In other words, a map scale provides the relationship between the map and the whole or a part of the earth’s surface shown on it. We can also express this relationship as a ratio of distances between two points on the map and the corresponding distance between the same two points on the ground.
17
Practical Work in Geography
There are at least three ways in which this relationship can be expressed. These are: 1. Statement of Scale 2. Representative Fraction (R. F.) 3. Graphical Scale Each of these methods of scale has advantages and limitations. But before taking up these issues, let us understand that the scale is normally expressed in one or the other system of measurement. You must have read and/or used kilometre, metre, centimetre etc. to measure the linear distances between two points on the ground. You might have also