The line of sight is kept as high above ground surface as possible to minimise the error in the
observed angles due to
(A) Shimmering
(B) Horizontal refraction
(C) Vertical refraction
(D) Both shimmering and horizontal refraction
observed angles due to
(A) Shimmering
(B) Horizontal refraction
(C) Vertical refraction
(D) Both shimmering and horizontal refraction