7/21/2019 Area by Triangles

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 Elementary Surveying Notes of AM. Fillone

METHODS OF DETERMINING AREAS

  Areas of land come in different shapes

  Some areas may be in the shape of a regular geometric figure, such as square, triangle, or

 parallelogram.

  Others may be quite irregular and may be bounded entirely by curved boundaries

 

The hectare (Ha) is the most commonly used SI unit of area1 hectare = 10,000 sq.m.

Methods used in determining areas

1.  use of triangles

2. 

the trapezoidal rule

3.  Simpson’s one-third rule

4.  The coordinate method

5.  The Double Meridian Distance (DMD) or Double Parallel Distance (DPD) method

6.  Coordinate squares

7.  Planimeter

AREA BY TRIANGLE

1.  Known base and altitude

2.  Two sides and included angle known/measured

3.  Three sides known/measured

B

h

A=(1/2)bh

AC

 b

 

a

 b

B

C A

c

A = (1/2) a b sin  

A

B

C

c

a

 b

A =  s (s-a)(s-b)(s-c)

s = (1/2)(a + b + c)