How do you read the vernier in theodolite?

To read the vernier on a theodolite, first ensure that the instrument is level and stable. Locate the main scale and the vernier scale; the reading is determined by finding the line on the vernier that aligns best with a line on the main scale. Count the number of whole divisions on the main scale up to this point and add the value of the aligned vernier division to get the final reading. This process allows for precise angular measurements, typically in degrees or minutes.