Transit Theodolite: Lower Scale Plate and Upper Scale Plate

Introduction:
A transit theodolite is a surveying instrument used for measuring horizontal and vertical angles. It consists of two circular plates, the lower scale plate and the upper scale plate. In this article, we will discuss the movement of both the plates in detail.

Both the Plates Can Move Independently:
The transit theodolite consists of a lower scale plate and an upper scale plate. Both plates can move independently of each other. This feature allows the surveyor to measure both horizontal and vertical angles. The lower scale plate is rotated horizontally, while the upper scale plate is rotated vertically. The surveyor can measure the angle between two points by rotating the plates and observing the readings on the scales.

Lower Scale Plate is Fixed:
In some theodolites, the lower scale plate is fixed. This means that it cannot be rotated independently of the upper scale plate. The lower scale plate is used to provide a reference point for the upper scale plate. The surveyor can rotate the upper scale plate and observe the readings on the lower scale plate to measure the angle between two points.

Upper Scale Plate is Fixed:
In some theodolites, the upper scale plate is fixed. This means that it cannot be rotated independently of the lower scale plate. The upper scale plate is used to provide a reference point for the lower scale plate. The surveyor can rotate the lower scale plate and observe the readings on the upper scale plate to measure the angle between two points.

Both the Plates Move Together:
In most modern theodolites, both the lower scale plate and the upper scale plate can move together. This feature makes it easier for the surveyor to measure angles between two points. The surveyor can rotate both plates simultaneously and observe the readings on both scales to measure the angle accurately.

Conclusion:
In conclusion, the transit theodolite consists of two circular plates, the lower scale plate and the upper scale plate. Both plates can move independently, or one plate can be fixed while the other moves. In most modern theodolites, both plates can move together, making it easier for the surveyor to measure angles accurately.