Tribrachs & Adapters

A tribrach is an attachment plate that can be used with a variety of survey instruments. Some of them include but may not be limited to: Theodolites Total Stations GNSS antennae Targets By using a tribrach with a laser plummet, you can be sure the instrument you use will be placed in the same position over a specific marker point and with a much greater level of precision.

If you want to get the most accurate measurements possible, your tribach will need to be adjusted so it’s perfectly level or plumb over a survey reference point. It uses an optical plumb sight that can be used as a vertical reference, but rough field conditions can move it out of alignment. This can lead to inaccurate measurements from your survey instruments. That’s why periodic readjustment is necessary to get the best results, which isn’t hard to do.

Most tribrachs have two small screws on the optical plumb arm under the instrument, which can be adjusted according to your needs. One of them adjusts the crosshair holder from left to right, while the other one moves it up and down. If you turn them simultaneously in opposite directions, you can move it diagonally. Use the tiny screwdrivers to move the crosshair holder until the hairs are centered on the mark at the center of the triangle. You have the right adjustment if all three sights hit the same plumb spot.

A laser plummet is an optical device that projects a consistent beam of light or infrared radiation in a vertical direction, which can be helpful if you need to get an accurate plumb line.