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Area Measurements

Area Measurements. Area from a map. 1- Dividing t he Area Into Regular and Irregular Shapes. 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

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Area Measurements

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  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= 70+30+100+….=1500 cm2 • Scale=1/2000 • Ground area= (1500x2000x2000)/ 100x100 • = 600000 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 = 0.995 rev • Reading around the required area = 5.765 rev • Scale of the map =1/5000 • Calculate the ground area

  9. Area from ground measurements

  10. 1- Use the field measurements 40m 50m A1 80m A2

  11. Area A1 • S= half the circumference of the triangle • S=(50+40+80)/2 = 85 • A1= • A1= • A1= 818.15 m2 • Total area= A1+A2+ irregular area

  12. Area is produced directly in m2

  13. Irregular Area

  14. Irregular Area • Simpson’s rule for curved boundaries • The line joining three offsets is assumed as a parabola • parabola • h1 h2 h3 • d d

  15. 2- Area from corner coordinates • 2 (x2,y2) • 1(x1,y1) 3(x3,y3)

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

  17. Area of circular segment

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