Plot the following cross-staff survey of a field and calculate its area in hectares. All distances noted in the field book are in metres
solution :
shows the plotting of field notes of the given area not to scale. The area Can be Found out in the Following manner.
1. Area of triangle AHB
= 1/2 x bx h
= 1/2 x (45-0)×35
=787.50m²
2. Area of trapezium HB CJ
= ( a+ b / 2 ) x d
= ( 35+25 / 2 ) x ( 70-45)
=750m²
3. Area of triangle JDC
= 1/2xbxh
= 1/2(80-70)x 25
= 125m²
4. Area of triangle IDE
= 1/2X bxh
= 1/2(80-60)×40
=400 m²
5. Area of trapezium IEFG
= ( a+ b / 2 ) x d
=( 40+30/2 )x (60-25 )
= 1225m²
6. Area of triangle AGF
= 1/2 bxh
= 1/2(25-0)×30
=375m²
Total area = 3662.50 m² ( or )
3662.50/10, 000= 0.36625 hectares