M3_C_L8: Permanent Adjustments of Vernier Theodolite

A Theodolite is very versatile equipment and can be used for many applications in land surveying. A theodolite is said to be in permanent adjustments if it satisfies all the relations among its fundamental lines. The permanent adjustment of an instrument usually gets disturbed due to its mishandling or after its prolonged use or its wear and tear. So, the state of relationship among different fundamental lines should be checked periodically and be reestablished, if necessary. In a perfectly conditioned instrument, the fundamental lines should bear following relationship: 1. The vertical cross hair should lie in a plane perpendicular to the horizontal axis. 2. The axis of each plate level should lie in a plane perpendicular to the vertical axis. 3. The horizontal axis should be perpendicular to the vertical axis. 4. The axis of the telescope level should be parallel to the line of sight. – or – when axis of altitude level tube is horizontal, vertical circle should read zero and line of sight should be horizontal 5. The line of sight should be perpendicular to the horizontal axis at its intersection with the vertical axis. Also, the axis of the telescope, and the line of sight should coincide. The permanent adjustments operations are based on the geometry of the fundamental line and thus, may disturb one relation while rectifying other. In order to avoid such possibility, the permanent adjustment should be done in the definite order. This video is an educational resource and is focused on introduction to fundamental axis & their relationship, Condition; test to assess adjustments and procedure for adjustment. Here as one learns the content he/she will be able to Demonstrate the fundamental relationship among axes of theodolite; Check the fundamental relationship among axes of theodolite and State the procedure to establish the fundamental relationship among axes of theodolite.