Fundamentals of Surveying (FS) Practice Exam

In differential leveling over long distances, which effect must be taken into consideration?

1. Focal length of the instrument

2. Curvature of the earth

3. Latitude of the observations

4. Atmospheric refractions

The correct answer is: Curvature of the earth

In differential leveling conducted over long distances, the curvature of the Earth is a significant factor that must be considered. As surveyors level between two points that are far apart, the Earth's surface curves away from a straight line connecting those points. This curvature can affect the accuracy of the height difference measurements. When working over large distances, the line of sight may not be horizontal due to this curvature, leading to potential errors in the determined elevations. To adjust for the curvature, surveyors must account for the Earth's shape and its effect on level lines, especially when the distance exceeds a certain limit, where the Earth's curvature becomes more pronounced. Considering the curvature helps ensure that the elevations obtained from differential leveling remain accurate and reliable, maintaining high standards in surveying practices. Other factors like focal length, latitude, and atmospheric refraction may influence readings but do not have the same direct impact on long-distance leveling as the curvature of the Earth does.