Angular Measurement
 Field Use of the
    Theodolite
 Taking Measurements
 Errors of Construction and
    Adjustment
 Collimation Error
 Horizontal Collimation
 Vertical Circle Index
 Plate Level
 Optical Plummet
 Miscentring
 Parallax in Telescope

Field Use of the Theodolite

Theodolites are robust scientific instruments designed for use in the field. They are used primarily for the measurement of angular values in a traverse or network between survey marks, and are also used for defining directions of lines of sight.

Setting Up

Most theodolites are set up in a similar manner to a dumpy level except they are usually centred over a mark on the ground. Many surveyors have their secret method for performing this task rapidly, acquired over many years of practice.

To review how to set up a theodolite see Setting Up an Instrument

The Concept Of Bearings

Surveying and navigation uses the concept of a whole circle bearing, consisting of 360° subdivided into the sexagesimal system. The determination of position on a plane can be calculated through simple vector mathematics, breaking the vector into its two constituent components (displacement in X or East, displacement in Y or North).

How to describe bearings using vectors is explained in greater depth in Coordinate Systems should you wish to review it.