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Q: An angle of 45⁰ with a chain line may be set out with .................
  • A. Optical square
  • B. Open cross staff
  • C. French cross staff
  • D. Prismatic square
Correct Answer: Option C - French cross staff – It is simplest types of cross staff which is commonly used. • It consist of octagonal brass box with slits cut in each face so that the opposite pairs from a sight line. By French staff angle measured 45⁰ and 90⁰. Optical square – A right angle is inserted on the survey line more precisely than the optical square. • It is works on the principle of double reflection of light Open cross staff = 90⁰ Prismatic square = 90⁰
C. French cross staff – It is simplest types of cross staff which is commonly used. • It consist of octagonal brass box with slits cut in each face so that the opposite pairs from a sight line. By French staff angle measured 45⁰ and 90⁰. Optical square – A right angle is inserted on the survey line more precisely than the optical square. • It is works on the principle of double reflection of light Open cross staff = 90⁰ Prismatic square = 90⁰

Explanations:

French cross staff – It is simplest types of cross staff which is commonly used. • It consist of octagonal brass box with slits cut in each face so that the opposite pairs from a sight line. By French staff angle measured 45⁰ and 90⁰. Optical square – A right angle is inserted on the survey line more precisely than the optical square. • It is works on the principle of double reflection of light Open cross staff = 90⁰ Prismatic square = 90⁰