Setting up of a Theodolite (Centering, Levelling and Focusing)

Summary

This video demonstrates the proper procedure for setting up, leveling, centering, and focusing a theodolite, an essential tool in engineering surveying. The step-by-step guide begins with setting up a wooden tripod, ensuring its stability, followed by centering the theodolite over a peg and leveling it using bubble adjustments. Detailed instructions for avoiding common mistakes, such as improper leg adjustments, are provided. The video concludes with tips on how to correctly focus the instrument and eliminate parallax error, ensuring accurate measurements. Viewers are encouraged to subscribe for more tutorials.

Takeaways

• 🛠️ The process begins by setting up the tripod, ensuring its top surface is at chest level, and tightening the screws.
• ⚖️ Proper positioning of the tripod involves spreading the legs equally and making sure the tripod head is approximately horizontal.
• 📍 One leg of the tripod is firmly pushed into the ground to stabilize it before mounting the theodolite.
• 📦 Careful handling of the theodolite is necessary when taking it out of the box, ensuring foot screws are at the middle mark before placing it on the tripod.
• 🔄 Centering involves using two legs of the tripod to align the theodolite with the marked peg on the ground, adjusting with minimal movement.
• 🔧 Leveling is done by adjusting the tripod legs until the Bullseye bubble is centered and further refined using the longitudinal bubble.
• 👍 The left thumb rule is key to adjusting the bubble to the center, using both foot screws simultaneously and moving the instrument as needed.
• 🔍 Focusing involves adjusting the Crosshair focusing screw first and then the object focusing screw for clarity.
• 📏 Removing parallax is essential by moving the head side to side to ensure no movement of the crosshairs with eye movement.
• ✅ The video concludes by demonstrating how to complete centering, leveling, and focusing, with references to previous tutorials on measuring angles.

Q & A

What is the first step in setting up the tripod for the theodolite?

The first step is to extend one of the legs of the wooden tripod and tighten the screw to ensure stability. The top surface of the tripod should be adjusted to the level of your lower chest.

How do you ensure the tripod head is approximately horizontal?

You can visually check by positioning yourself behind the tripod and looking through the tripod head to see if it is approximately horizontal. Adjust the tripod legs as needed.

What should you do before placing the theodolite on the tripod?

Before placing the theodolite on the tripod, ensure that the foot screws are set to the midrange, as indicated by a horizontal mark on the screws.

How is the theodolite centered over the peg using the tripod legs?

First, firmly push one leg into the ground, and use the other two legs to adjust the position until the optical plummet shows that the theodolite is centered directly over the peg.

Why is it important not to lift the legs of the tripod once they are set in the ground?

Lifting the tripod legs after they are set can cause the theodolite to lose its centered position, requiring readjustment. Instead, adjust the alignment using fine movements of the legs.

How do you bring the Bullseye bubble to the center?

To center the Bullseye bubble, adjust the tripod legs by loosening the screws and extending the legs. The goal is to align the air bubble within the yellow circle of the Bullseye bubble.

What is the left thumb rule when adjusting the longitudinal bubble?

The left thumb rule states that if your left thumb moves in a certain direction while adjusting the screws, the bubble will move in the same direction.

How do you ensure that the theodolite is properly leveled?

After adjusting the Bullseye and longitudinal bubbles, recheck that both are centered. If they shift during the process, use the tripod legs and the left thumb rule to bring them back to the center.

What is parallax error, and how do you remove it during focusing?

Parallax error occurs when the crosshairs and the object are not in the same focal plane, causing movement between them as you shift your eyes. To remove it, adjust the focusing screw and move your head side by side until the crosshairs and the object stay aligned.

What are the main screws used for focusing the theodolite?

There are two main focusing screws: the Crosshair focusing screw, which sharpens the crosshairs, and the Object focusing screw, which brings the target into focus.