Three angular measurements taken at different times with differentinstruments close the horizon plane. Each setup involved different instruments, different crews, using different measurement techniques. The measurements span a period of over 25 years. Obviously the measurements are independent of each other. The chief surveyor has sat down and estimated the precision of each measurement based on his experience. The office needs the least squares estimate of each angle. Data 1 8317' 35" 19.9" 2 134 38' 56" 16.7" 3 142 03' 14" 14.3