What is the method for calculating the elevation difference between two points with the same instrument setup?

The method for calculating the elevation difference between two points with the same instrument setup involves subtracting the backsight from the foresight. This process is based on the principles of leveling in surveying, particularly in techniques such as differential leveling.

When a surveying instrument is set up, it allows for the measurement of the height of a staff (or rod) placed at different locations. The backsight reading is taken on a staff positioned at a known elevation point, while the foresight reading is taken on a staff positioned at the point where the elevation is unknown.

To find the elevation difference, you measure how much higher or lower the foresight reading is compared to the backsight reading. Thus, the calculation involves taking the foresight reading and subtracting the backsight reading. This gives a direct measurement of the change in elevation between the two points, which is essential for accurate leveling and topographical surveys.

Other methods presented in the options do not provide a straightforward calculation of the elevation difference as required in this scenario. For instance, using an average of two elevation readings might provide a rough estimate but does not specifically yield the elevation difference between two distinct points. Adding the foresight and backsight readings does not reflect the difference in elevation and instead combines the two