Tips on centering errors for dual-axis compensators and sun effects on tubular vials.
A: You are absolutely correct to be concerned. As long as the magnitude and impact of the error is unknown, you will not be confident that the work you do is of sufficient quality. First, you should evaluate the limits of the compensator's range. This will give you some idea of the maximum tilt you might possibly work under. Second, determine the maximum height of your instrument setup. The distance is determined from the survey point to the center of the horizontal circle of your instrument. Third, perform a simple calculation to determine the maximum centering error (see Figure 1). If the maximum tilt range of the compensator is 10 arc minutes and the maximum height is 4.5 feet, then the maximum error will be: