Point 1 having an elevation of 120 m above datum, and 2 is point of unknown elevation. By means of an instrument set 1.20 m above 2, vertical angle is observed that point 1 being 14° 45'. Point 2 is higher than point 1. The horizontal distance between point 1 and 2 is 547.20 m. Making due allowance for earth's curvature and atmospheric refraction. Compute the difference in elevation between point 1 and 2.

Problem 4. Point A is in between points B and C, the distances of B and C from B and C from point A are 1000m and 2000m respectively measured from point A. The angle of elevation of point B is 18°13' while that of C as Ø. The difference in the elevation of B and C is 44.4m. Considering the effects of curvature and refraction, what is the value of Ø? (Note: Assume that point C is higher) where: Earth's Curvature and Atmospheric Refraction Correction (Her): Her(m) = 0.067 K² K (km) = level distance Her K Vertical line Horizontal line Level line