- Exploring land for a potential building requires marking wall and foundation boundaries using accurate angle calculations. Many surveyors use electronic theodolite devices for viewing or observing an area. These devices offer accurate angle measurements for determining structural dimensions and plot boundaries. However, the theodolite cannot provide accurate measurements unless it is periodically calibrated, especially if the workshop has excessive machine vibrations and wind.
- Place the theodolite on a roughly leveled tripod. Check that the legs of the tripod are firmly pressed into the ground for stability.
- Align the theodolite with its basic leveling screws by observing the level of the base. Make sure the bubble is perfectly centered in the visible part.
- Put a goal about 300 meters away. The target must resemble a plus sign or a visor.
- Look through the eyepiece of the theodolite. Align the internal crosshair of the theodolite with the crosshairs of the target. Note the vertical angle that appears on the front of the theodolite.
- Stay in the same position. Turn the theodolite around. Rotate the eyepiece until the user can see the target again without moving the position.
- Repeat step 4. The vertical corners must match exactly. If the vertical angles do not match, reset the electronic parameters of the theodolite with the reset button, and effectively calibrate the theodolite to new precise values.
- Repeat steps 4 and 6 for the calibration of the horizontal angle.
- Test the theodolite with a set of known angle values, such as at the baseline of an expert. The corners must match the known values.
Every theodolite manufacturer uses a different button or buttons to reset the calibration values. Refer to the user manual for specific model instructions. For some calibration resets, multiple buttons must be pressed in succession to prevent accidental calibration changes while working in the field.
Do not attempt to calibrate a damaged theodolite, especially if the outer casing is cracked or broken. A professional repairer must assess damaged instruments. Sensitive optics may require internal physical adjustments, rather than a simple electronic calibration adjustment.