What is the purpose of leveling a transit using the bubble vial?

Leveling a transit using the bubble vial is primarily aimed at ensuring proper alignment with the horizon. The bubble vial is a pivotal component in achieving a horizontal plane, which is essential in surveying tasks. When the transit is level, it guarantees that all measurements taken will be accurate and reliable, as it maintains a consistent reference to the earth's surface.

This correct alignment helps reduce errors in elevation readings, which is critical for construction projects where precise leveling is necessary. While improving sighting accuracy is a related benefit, the main purpose of leveling is to ensure that the instrument is properly aligned with the true horizontal plane. Consequently, if the transit is not leveled correctly, it can lead to significant inaccuracies in measurements and calculations, affecting the overall quality and integrity of the project being undertaken.