How to Use a Transit Level Instrument

A transit level is a device that is used to measure the relative horizontal and vertical angles from one object or place to another object or place. Used primarily during land surveying, these devices come in many different sizes and configurations depending on the device manufacturer and the specific job or task being measured. The basic method of using a transit remains constant regardless of the make or model of the transit being used. By following a few basic guidelines, a beginner can easily learn to use a transit accurately, and will feel comfortable using a base model instrument from almost any manufacturer.

Things You'll Need

• 300-foot tape measure
• Measurement rods (if not included with transit)

Instructions

1. Setup the tripod that holds the transit instrument by placing it in an approximately level position in the area where you require measurements. It should be placed on stable ground, so that the tripod legs will not gradually sink into mud or any other soft surfaces. Adjust the legs of the tripod as necessary to get the top mounting base of the tripod level. The transit will sit on the mounting base once it has been prepared.

2. Drive the tripod legs into the ground by stepping on the protruding leverage prongs. Make sure the tripod is secure before placing the transit level on top of it to reduce risk of damage if it were to slip off. Measurement accuracy is best when the tripod is on a hard firm surface.

3. Mount the transit level on top of tripod. Screw the transit to the tripod by using mounting screws or clips as provided by the manufacturer. Check that it is secure. Release the horizontal clamp screws. Turn the transit level around until the telescope bubble is directly over the pair of leveling screws. This will allow the unit to be properly calibrated prior to use.

4. Calibrate the transit so that it is completely level by turning the thumbs screws (calibration screws) away or towards one another; this will cause one of the screws to become tighter while the other becomes looser. Watch the calibration bubble visible in the top of the transit.

5. Slowly repeat this adjustment procedure until the telescopic bubble located on the top of the transits level is exactly centered. When the bubble is exactly centered between the two hash marks seen in the alignment window, that means the transit is calibrated to a perfectly level configuration along one plane of reference (axis).

6. Turn the telescope portion of the transit exactly 90 degrees until it is located over the other set of leveling screws. Repeat the leveling sequence using this third adjustment screw to level your transit along its second axis. Keep repeating this procedure until transit is completely level on both axis.

7. Check the accuracy of the transit adjustment by positioning a measurement rod (included with the transit) 110 feet away from the transit. Push it into the dirt vertically so that it is stable. Place an additional measurement rod in position on the other side of the device, also 110 feet away. The transit device should be centered midway between the two points.

8. Take a reading from the transit of each rod, and note the exact reading given by the transit. Move the transit level to another area along the same 220-foot line, either forward or backwards, then measure both rods again. Make sure transit and tripod are firmly set up and are level before taking your measurement.

9. Calibration is perfect when each measurement taken results in the same reading. If the instrument cannot be calibrated accurately, it should be taken to a professional technician to repair the problem. Once calibration is complete, you may now use the transit to take accurate measurements of your project.

10. Measure your actual project or test by peering through the eyepiece of the telescope and line up a measurement stick or rod with the cross hairs seen within. Use the focal screw to help bring your viewing into focus by turning it clockwise or counterclockwise as necessary. When measuring your project or test, be sure you place your rods accordingly. Read the measurements given by the transit for those locations.

References

• New England Laser: How to use a transit