What is tachometer in surveying?

A tachometer is generally a transit theodolite having a telescope fitted with a stadia diaphragm i.e., a telescope equipped with two horizontal hairs called stadia hairs. The additional hairs are equipped from the central one and are also called stadia lines.

Characteristics of tachometer: –

• Value of the multiplying constant (f/i) should be 100.
• The magnification of the telescope is between 20 to 30.
• The eye-piece should be greater magnification.