Devices to Measure Angles

Protractor

• A protractor is shaped like a half-circle with a straight base and is commonly made of clear plastic or thin metal. The center of the straight-edge base is marked and is used to line up the meeting point of the two lines that comprise the angle. The half-circle shape has numbers that range from 0 to 180 degrees. The center line on the half-circle is 90 degrees, and the small indicator numbers all along the half-circle are degrees of measurement. The protractor is used to measure angles on drawings or blueprints.

Taper

• A taper is a device used to measure the angle of a tapered hole. For example, if you drill a cone-shaped hole in a piece of plywood and need to know the angle of the cone, you would use a taper. There are two long measuring rods connected at one end and a measuring pin with an angular scale on the other end to indicate the angle.

Theodolite and Transits

• Theodolites and transits are pieces of equipment used by surveyors to measure large construction angles. They are used to determine the slope of a piece of land prior to construction or to make sure that a structure is level during construction. Theodolites and transits serve the same purpose, but a theodolite is considered to be more accurate, according to the Purdue School of Engineering website. Transits use metal circles as angular scales, while theodolites use glass circles. These are the rings built into the devices that are used to gauge the angle against the horizon.

Clinometer

• A clinometer is used to determine ground elevation in relation to where you are standing. It helps to determine the slope of the ground by measuring the angle of an incline versus a horizontal line of sight in the device. Clinometers can come with a digital display that makes it easier to determine the accurate slope of a terrain.