1. Area Measurements

2. Area from a map

3. 1- Dividing the Area Into Regular and Irregular Shapes

4. Measure the dimension of each area
Calculate the area of each part
Calculate the sum of the regular and irregular areas
Convert the map area to a ground area
Example
Total map area= ….=1500 cm2
Scale=1/2000
Ground area= (1500x2000x2000)/ 100x100
= m2

5. 2- Graph Paper Method Plot the area on a graph paper
Count the number of sq cm and sq mm
Convert the map area to a ground area using the known scale

6. 3- The Planimeter Method
Mechanical planimeter
Digital planimeter

7. tracing needle
fixed block

8. Calibrate the planimeter before using it
Make reading around a known area
Example:
reading around a 10x10 cm square area = rev
Reading around the required area = rev
Scale of the map =1/5000
Calculate the ground area

9. Area from ground measurements

10. 1- Use the field measurements

11. Area A1
S= half the circumference of the triangle
S=( )/2 = 85
A1=
A1= m2
Total area= A1+A2+ irregular area

12. Area is produced directly in m2

13. Irregular Area Trapezoidal rule
Each area is assumed as a small trapezoid
Simpson’s rule for curved boundaries
The line joining three offsets is assumed as a parabola
parabola
h h h3
d d

14. 2- Area from corner coordinates
2 (x2,y2)
1(x1,y1) (x3,y3)

15. Notes
Points should be numbered in clockwise direction
Divide the result by 2 to obtain the area