Determination of areas

UNIT – II

Chapter - 3 (D)

DETERMINATION OF AREAS

AREA OF LAND

One of the main purposes of land surveying is to determine the AREA of a tract (piece) of the land surveyed and also to determine the quantities of earthwork.

1. UNITS ADOPTED FOR THE MEASUREMENT OF AREAS

• The square meter (sq. m.)

• The are = 100 square meters

• The hectare = 100 ares = 10,000 square meters

The square kilometer = 100 hectares = 10,000 ares = 10,00,000 square meters

The areas of agricultural lands are measured in hectares. Areas of urban properties are measured in square meters. Very large areas of land are measured in square kilometers.

In practice, land owned by an individual or a concern exists with irregular boundaries with ups and downs. For calculation purposes, the land is assumed as plane surface.

2. METHODS OF DETERMINING AREAS

Areas may be computed by the direct use of field measurements made at the site and also from the previously plotted plan of the land. To calculate the area, offsets are measured from the boundaries to the survey line or base line at regular intervals. In the case of previously plotted plan, the offsets to a base line can be scaled off. :

Method of determination of areas based on Field Measurements Directly made at the Site is convenient for small areas of land. On the basis of this, the following two methods are used to determine the area of the land:

• By dividing the Area into a Number of Triangles

• By Offsets from Base Line, using the following four Rules:

1. RULE I: Mid-Ordinate Rule

2. RULE II: Mean Ordinate Rule or Average Ordinate Rule

3. RULE III: Trapezoidal Rule

4. RULE IV: Simpson's Rule