Setup the Vernier Theodolite for Angular Measurements
The Vernier theodolite is a versatile device used for angular measurements and can be used to replace a compass. To use the Vernier theodolite, it is necessary to understand how to set it up correctly. This involves making sure it is leveled, the telescope is properly aligned, and the vertical and horizontal axes are calibrated.
Leveling the Vernier Theodolite
The Vernier theodolite needs to be leveled in order to ensure an accurate reading. This can be done by adjusting the tripod legs so that the instrument is stable and the bubble level is in the center.
Aligning the Telescope
Once the Vernier theodolite is level, the telescope needs to be aligned. This is done by pointing the telescope at the target and making sure that the crosshairs are aligned with the target.
Calibrating the Axes
The next step is to calibrate the axes by adjusting the two knobs on the Vernier theodolite. The horizontal axis should be adjusted to match the direction of the target, while the vertical axis should be adjusted to match the angle of the target.
Measuring Horizontal and Vertical Angles with a Vernier Theodolite
Once the Vernier theodolite is set up, it is ready to use for measuring angles. To measure a horizontal angle, the telescope should be pointed at the target and the angle should be read off the scale. To measure a vertical angle, the vertical axis should be adjusted until the angle of the target is aligned with the horizontal axis, and then the angle should be read off the scale.
Working of Vernier Theodolite
Vernier Theodolite: Setting Up and Adjustment
When using a Vernier theodolite for measuring angles, the first step is to ensure that the instrument is properly set up and adjusted. This involves aligning the theodolite, adjusting the levels, and aligning the optical axis. Once these steps are completed, the theodolite is ready for angle measurements.
Aligning the Theodolite
The first step in setting up a Vernier theodolite is to align the instrument. This involves orienting the theodolite so that it is level and centered on the point to be measured. To ensure accuracy, a bubble level is used to make sure the instrument is properly aligned.
Adjusting the Levels
Once the theodolite is properly aligned, the next step is to adjust the levels. This is done by adjusting the two leveling screws located on the base of the theodolite. The adjustment should be made in small increments, until the bubble level is centered.
Aligning the Optical Axis
The final step in setting up a Vernier theodolite is to align the optical axis. This involves rotating the telescope until the crosshairs are centered on the point to be measured. Once the optical axis is properly aligned, the theodolite is ready to be used for angle measurements.
Temporary Adjustment of Theodolite
Following are the adjustment required for theodolite before using it:
- Setting
- Centering
- Leveling
- Focusing
Setting of Theodolite
Step 1: Setting the Tripod
Setting up the tripod is the first step in theodolite setup. Unfold the tripod and place it on the ground with all legs in the same level. Level the tripod by just eye estimation.
Step 2: Suspend a Plumb Bob
From the bottom of the theodolite, suspend a plumb bob to set the instrument over the station mark. This allows you to ensure that the theodolite is accurately aligned and ready for use.
Centering
Centering: A Step-by-Step Guide
Centering is the process of aligning the vertical axis of an instrument with a plumb line. To ensure accuracy in this process, the tripod stand should have legs of equal height and be placed on level ground. Additionally, each leg should be equipped with a cone-shaped metal shoe to prevent movement.
Leveling of Theodolite
How to Level a Theodolite
Theodolite leveling is a process used to make sure the vertical axis of the instrument is truly vertical. This is done by centering the bubble in the level tube by rotating the foot screws. It is important to check that the bubble is centered in all directions of the telescope, and that it does not move while taking readings.
Focusing
- Determination of Horizontal Angle ABC:
The horizontal angle ABC between three points A, B and C on the same ground level can be determined by using a theodolite. After temporarily adjusting the theodolite, the telescope is located at one point (A) from which the other two points (B and C) must be focused to measure the angle. The following steps explain the procedure for measuring the horizontal angle ABC:
- Step-by-Step Procedure for Measuring Horizontal Angle ABC:
Step 1 – Set up the theodolite at point A and focus it on point B.
Step 2 – Rotate the theodolite and measure the angle between A and B (angle AB).
Step 3 – Rotate the theodolite again and measure the angle between A and C (angle AC).
Step 4 – Calculate the angle ABC by subtracting angle AB from angle AC. - Benefits of Measuring Horizontal Angle ABC:
This procedure of measuring horizontal angle ABC is useful in many surveying applications, such as establishing the orientation of buildings, roads, and other structures. It can also be used to measure the angles of a triangle, helping to determine the area of the triangle.
Measurement of Horizontal Angle using Theodolite
Calculating Angle ABC using Theodolite
The process of finding the angle ABC using theodolite is relatively simple. First, the theodolite is adjusted so that the telescope is located at a point, A. Then, the telescope needs to be focused on the other point, B, so that the horizontal angle between A and B can be calculated. Once the angle is calculated, the telescope needs to be moved to point C, and the angle between B and C can be calculated. The angle ABC is then determined by adding the two angles together.
Procedure for Measurement of Horizontal Angle
Step 1: Set the Vernier Readings
To begin, the Vernier A reading must be set to zero and the Vernier B reading must be set to 180. This can be done by releasing the upper clamp screw and tightening the lower clamp screw. Once the readings have been set, the upper clamp screw should be tightened and the upper tangent screw should be used to check for any errors.
Step 2: Focus the Ranging Rod at Location A
Next, the ranging rod at location A should be focused and bisected. To do this, the lower clamp screw should be loosened so that the telescope can be rotated without changing the readings.
Step 3: Rotate the Telescope to Location C
Once the ranging rod at location A has been bisected, the upper clamp screw should be released and the telescope should be rotated in a clockwise direction towards the ranging rod at location C. The rod should then be bisected and the Vernier reading should be noted. This reading will be the horizontal angle between locations A and C, or angle ABC.
Step 4: Measure the Angle in Both Directions
If the vertical circle is on the left side of the telescope, the same procedure should be repeated with the vertical circle on the right side. The average value of the angles obtained in both directions will give a more accurate value of the horizontal angle.
Measurement of Vertical Angle using Theodolite
How to Measure Vertical Angle Using Theodolite:
- Adjust the Theodolite:
To begin the process, adjust the theodolite temporarily and set the Vernier reading of the vertical circle to 0, focusing it to point C. Ensure that the bubble is centered using the foot screws without any collimation error. - Bisect Point A and B:
Once the theodolite has been adjusted, slowly raise the telescope towards point A, bisecting the point A and noting down the Vernier reading angle AOC. Similarly, bisect the point B from C, obtaining the angle BOC. From these readings, we can calculate the vertical angle AOB. - Final Step:
Finally, conduct the procedure in both face left and face right conditions and take the average value as the accurate vertical angle.