What is a correct check work formula for level readings?

Answer: C — ΣBS - ΣFS = ΣLast RL - ΣFirst RL

The formula involving level readings is essential for ensuring accurate surveying and leveling in construction projects. The correct choice indicates the proper relationship between the backsights (BS), foresights (FS), and the benchmark elevations (RL). In this context, the total backsights measured during the survey are added up, and the total foresights are subtracted. This calculation relates the final reduced level (Last RL) and the initial benchmark level (First RL). The equation suggests that the net difference in height observed from the backsights to the foresights should equal the elevation change from the starting reference (First RL) to the ending observation point (Last RL). Thus, the core idea is that the sum of the backsights minus the sum of the foresights gives the overall vertical distance change represented by the difference in reduced levels—showing the relationship of the survey points in the field. This formula effectively helps verify accuracy in leveling and ensures that no errors occurred during the measurement process.