After reading this article you will learn about:- 1. Description of a Transit Vernier Theodolite 2. Terms Used While Manipulating a Transit Theodolite 3. Fundamental Lines of a Transit Theodolite 4. Adjustments of a Theodolite. Description of a Transit Vernier Theodolite: [Figs. 9.1. a&b]: A transit vernier theodolite essentially consists of the following parts: 1. Levelling Head: This supports the [...]
The theodolite is most accurate instrument used mainly for measuring horizontal and vertical angles. It can also be used for locating points on a line, prolonging survey lines, finding difference in elevations, setting out grades, ranging curves etc. Theodolites are primarily classified as: (1) Transit, and (2) Non transit. A theodolite is called to be transit when its telescope can [...]
There are three methods of measuring horizontal angles: 1. Ordinary Method. 2. Repetition Method. 3. Reiteration Method. 1. Ordinary Method (Fig. 9.6.): To measure horizontal angle AOB: (i) Set up the theodolite at station-point O and level it accurately. (ii) Set the vernier A to the zero or 360° of the horizontal circle so do this, loosen the upper clamp [...]
After reading this article you will learn about the direct vernier and retrograde vernier . 1. Direct Vernier: Principle: If it is required to read 1/nth part of the smallest division on the main scale, (n-1) main divisions are taken and divided into n equal divisions on the vernier scale as shown in Fig. 9.2. Here 9 divisions on the [...]
Sources of error in theodolite work are classified into three groups: 1. Instrumental Errors 2. Observational Errors 3. Natural Errors. Source # 1. Instrumental Errors: (i) Non-adjustment of plate levels: If the plate levels which are not perpendicular to the vertical axis, are centered, the vertical axis of the instrument is not made truly vertical. As a result, the horizontal [...]
There may be two cases to find height of an object using a theodolite: 1. When he base of the object is accessible. 2. When the base of the object is inaccessible. 1. Base of the Object being Accessible (Fig. 9.13): To find the height of the object above a Bench Mark (or above the instrument-station): Let H = the [...]
The chief methods by which the relative directions of lines may be determined are: 1. Theodolite Traversing by Directs Observation of Angles 2. Theodolite Traversing by Direct Observation of Bearings. Method # 1. Theodolite Traversing by Directs Observation of Angles: In this method, the angles between the successive lines are measured, and the bearing of the starting line is observed. [...]
The permanent adjustment in case of a transit theodolites are: 1. Adjustment of the Horizontal Plate Levels: The axis of the horizontal plate levels must be perpendicular to the vertical axis. 2. Collimation Adjustment: The line of collimation should coincide with the axis of the telescope and axis of the objective slide and should be at right angles to the [...]
Adjustment of a closed traverse includes: 1. Adjustment of Angular Error. 2. Adjustment of Bearings. 3. Adjustment of Closing Error. 1. Adjustment of Angular Error: (a) Angular Error: The theoretic sum of the interior angles of a traverse should equal (2N-4) right angles, and that of the exterior angles should equal (2N+4) right angles, where N is the number of [...]