 In today's session we are going to discuss on a topic advance instrument in that we focus on Theodoroid, Myself, Bipin Patil, Assistant Professor, Department of Civil Engineering, Vulturen Institute of Technology, Sulapur. These are the learning outcomes for today's session. So at the end of this particular session, learners, students will be able to explain about Theodoroid, concept of Theodoroid, its working principle and function. First thing, what is Theodoroid? Observe these pictures, digital Theodoroid, one near Theodoroid, different front elevation is present here, captured view, side elevation, telescope is present here, vertical disk, horizontal disk, linear microscrews are present here, bubble tube. So what do you mean by Theodoroid? Basically these two instruments, first one instrument which is used in surveying to measure horizontal vertical angles with a small telescope, with a small telescope that can move in the horizontal and vertical planes. So you just observe this picture, it moves in a horizontal direction, it moves in a vertical direction. So easily you can identify the vertical angles, also horizontal angles. Similarly for this digital Theodoroid, this is nothing but your one near Theodoroid, this is digital Theodoroid. Theodoroids are electronic device regarding this instrument, are widely used for the measurement of vertical and horizontal angles. The purpose is same regarding these two instruments. Here we are identifying the angles, vertical, horizontal, here also same. Now here we are using the one near, one near readings and here we are using the digital. So these particular instruments are used in the construction industry to identify the angles. What do you mean by Theodoroid surveying? By using this instrument, whatever the surveying work is carried out, we called as Theodoroid surveying. A system of surveying in which the angles are measured with the help of Theodoroid. These particular angles are measured vertical angle, horizontal angle with the help of Theodoroid. It is called as Theodoroid surveying. Two pictures are continuously I am using for next slides also. Uses of Theodoroid, basically why you are using Theodoroid. First one, measuring horizontal and vertical angle. So for digital Theodoroid we require some input data including climates also. And here you have to fix the horizontal and vertical linear, one near readings. And according to that vertical distance and horizontal distance is used to identify the angles. Second one, locating points on a line. We are using Theodoroid. Third one, prolonging the survey lines for root survey work, for canal work, then for a railway track preparing to identify the survey line, to prolong the survey lines we are using Theodoroids. Finding the difference of the levels we are using such types of Theodoroids. In curves, Theodoroid plays a vital role. Ranging curves, to prepare a curves, different types of curves are present. So in such cases we are using Theodoroid very widely. And each and all tachymetric survey work based on this Theodoroid. In tachymetric survey work we are considering the constants. So here basically to identify the angles, to identify the distances, to prolonging the survey work, to identify the straight line path, to identify the bearings with respect to non-direction we are using this particular Theodoroid. Next one, classification of Theodoroid. Theodoroid may be classified as basically two parts are present. One is your transit Theodoroid and non-transit Theodoroid. We will discuss in detail. And second one, varnier Theodoroid and micrometer Theodoroids are there. What do you mean by transit Theodoroid? See here. A Theodoroid is called transit Theodoroid. When, so same Theodoroid is present here. When its telescope can be transited. A telescope can be transited. That is revolved through a complete revolution. Through a complete, it may be vertical, it may be horizontal. Revolved through a complete revolution about its horizontal axis. Horizontal, fundamental axis are present in the vertical plane we called as transit Theodoroid. And similarly, non-transit Theodoroid means the telescope cannot be transited. Here the telescope is transited and revolved through a complete revolution about the horizontal axis in the vertical plane. And here it cannot transit it. So transit Theodoroid, non-transit Theodoroid. Varnier Theodoroid. We are using varnier in that. For adding the graduated circle, if varniers are used in a Theodoroid, we called as varnier Theodoroid. And instead of that, if I put micrometer to identify these particular readings, we called as micrometer Theodoroid. If a micrometer is provided to read the graduated circle, the same we called as micrometer Theodoroid is there. Nowadays basically, varnier type of Theodoroids are commonly used to identify the angles, to identify the distances and remaining some survivors. Basically, the adjustment of Theodoroid is done by two ways. First one, permanent adjustment. Second one, temporary adjustment. We will discuss in detail permanent adjustments. The permanent adjustments are made to establish the relationship between the fundamental lines of the Theodoroid. Now as I mentioned here, this is your tripod. Horizontal disc is present here on horizontal plane, vertical plane, vertical disc, telescope, eyepiece, object glass, varnier adjustable screws. This is your tri-batch. Bubble tubes are present here. So now, these are the axis are present. These axis, then the vertical axis, horizontal plane, some relationships are present. Adjustment of horizontal plate levels. First one, that is the horizontal plate level you have to adjust it. The axis of the plate levels, so it may be horizontal axis, vertical axis, must be perpendicular to the vertical axis. Or the axis of the plate. Suppose if I consider horizontal plane, so the axis of this particular plate must be perpendicular to the vertical axis. Means vertical axis. Collimation adjustment. The line of collimation should coincide with the axis of the telescope. So line of collimation it is present here, should coincide with the axis of telescope, axis of telescope now present here. So axis of telescope should coincide with line of collimation. And the axis of the object or object to slide should be right angle to the horizontal axis. Next one, horizontal axis adjustment. Your horizontal axis must be perpendicular to the vertical axis. So what is the vertical axis is present here, perpendicular to the horizontal axis and vice versa. Next one, the adjustment of telescope level or we called as altitude level plate levels. Adjustment of the altitude level plate level. So the axis of telescope, so observe here the axis of the telescope levels or the altitude level must be parallel to the line of collimation. The axis of the telescope level or altitude level must be parallel to the line of collimation. And last one that is the vertical circle index adjustment. The vertical circle Vernier in this particular vertical circle, whatever the Vernier is present that Vernier must read 0 when the line of collimation is horizontal. When the line of collimation is horizontal, so in that case the vertical circle Vernier must read 0. These are nothing but your permanent adjustment of theodolite. Now the temporary adjustment of your theodolite. Basically for any type of work, this temporary adjustment is essential. So the temporary adjustment are made at each setup of the instrument before we start taking observations with the instrument. So primary three points are present here. One is your centering, next one the leveling and last one the focusing. First tripod you have to set it. Then mount this particular instrument over the tripod and carry out the centering process. So in your centering process you just observe, you just use the plumb ball and try to identify the centering. Otherwise use this particular object glass is present here and observe your centering point that is on the present on the ground level. After the centering process is over, you move towards leveling. Plate level is present here, foot screws are present. Slightly use two foot screws and try to bring this plate level over to exactly at a central position. Or easily you can carry out the leveling process. After that use eyepiece, object glass and try to adjust the parallax. So this process is nothing but the focusing. So my now dear friends you just try to pause the video, try to give the answer of this particular question. And the answer of this particular question. To prepare this particular session I refer these were the references. Thank you.