How Does a Transit Level Work?

When you need to find out if something is level in your home, a hand held level can be the answer. However, if you need to make a level measurement outside and it involves making multiple readings over 100 feet from each other, that hand level is useless. You need a device that can provide you with uniformity and accuracy of multiple readings. The instrument you need is a transit level, which is a precision telescope used for land measurements.

Mounted on a tripod, a transit level is both portable and weather resistant. Neither heat nor cold affects the transit level because of its built-in durability. It even has sunshade incorporated into the lenses for optimal viewing outdoors. Damage occurs only if dropped, which will cause its reflective lenses to come out of alignment, rendering the instrument useless. Only a professional can restore the precise angles necessary to produce accurate levels that you can trust.

What you need to level determines where you should place the transit. If you are measuring a line of things all in a row such as fence posts, then place the transit at the beginning of the line. Adjust the tripod legs until the transit is stable.

The next step is to adjust the bubble in the glass vial. Turn the A and B screws until the bubble aligns with the A/B axis. Then turn the transit a quarter turn to the C/D axis and level the instrument again. Recheck each position several times to make sure that it is level. Once leveled, you can turn the transit on the tripod 360-degrees and the entire circle it points at will be level as well.

A transit normally comes with a measuring stick that is marked in 1-inch increments. The helper or spotter stands by the desired location holding the measuring stick plumb or vertical and the transit user looks through the transit eyepiece. Crosshairs similar to a submarine periscope enable the operator to make the alignment. When the measuring stick's predetermined benchmark height is directly in the crosshairs, then the height of that location is noted. The helper then moves the measuring stick to the next location and the operator makes another location reading.

You can also use a transit level to determine if something is plumb or straight up and down. Making sure that a building structure is still sound and that the forms are true and checking pole alignments for vertical straightness are two uses requiring the plumb feature.