What is the most important surveying instrument?

Regardless of the type of surveying you are involved with, there are specific instruments that you may consider essential for the job. These instruments include a solar compass, an object vane, a total station, a cross-staff, and an Altazimuth theodolite.

Object vane

Object vane is one of the most important surveying instruments. It is used for observing luminous objects. It also helps the operator to determine the line of sight. It consists of a metal frame hinged on a box and carries a thin wire at the centre.

It is a simple instrument mainly used in mine surveying. It has a magnetic needle with a graduation circle attached to the magnetic needle. The magnetic needle can be positioned on the compass pivot or the top box. 

An object vane is used for observing luminous objects. It has a fine silt-like part at the centre and a thin black wire at the edge. The object vane can be mounted in front of the eye obliquely. It can be used in conjunction with the prism. The object vane can also be used to measure the angle of a distant object.

Solar compass

Initially, the solar compass surveyed areas with iron-bearing mineral deposits. Iron in the ground disturbed the magnetic compass and made the readings inaccurate. Then, in the 1850s, the General Land Office adopted the solar compass as a standard instrument. The Solar Compass became a favourite for land surveying throughout the twentieth century.

As a surveyor, William Austin Burt used his knowledge of astronomy to design a compass that could be used to find the true north. His invention was called the solar compass, and Burt patented it in 1836. He received several awards from the exhibition holders for his achievement in science.

The surveyor would set up the instrument and rotate it until the lens bar pointed at the sun. The sun’s rays would pass through the lens and focus on the crosshatched lines on the target area.

In the 1840s, Burt presented his new devices to the Franklin Institute in Philadelphia. He was awarded the Scott’s Medal for an “ingenious instrument” by the institution.

He then petitioned the United States Congress to renew the patent for his solar compass. The United States government adopted his invention as a standard instrument for surveying land. The solar compass proved to be more accurate than the magnetic compass. The United States government also required surveyors to use the solar compass to find the true north.

Altazimuth theodolite

Theodolites have existed in different forms since the sixteenth century. They can be divided into three major categories. The first is the transit theodolite, which reads angles directly to 30 arc seconds. Another type is Everest’s Tribrach, which has a lower center of gravity and is therefore suited to forested terrain. Finally, there is the non-transiting type, which is less common.

A common theodolite is generally made of brass and has a larger graduated ring. A surveyor’s compass is usually mounted in the center. Three screws allow the theodolite to be adjusted. The tripod should be extended to a comfortable level for the user.

Another method for measuring distances is with verniers. Verniers measure centigrade minutes of *01 grade. The instrument can be read with computer circuitry. The readings can be used to position objects in accordance with existing plans.

Theodolites have also been manufactured to track the horizontal angles of special weather balloons. These instruments have been designed to balance the trunnion and read in seconds.

Cross-staff

Throughout the history of surveying, the cross-staff was a vital instrument to help set out right angles and to measure distances. Surveyors and astronomers used it to make accurate measurements.

Several different models of cross-staff exist. These include the open cross-staff, French cross-staff, and octagonal cross-staff.

Open cross-staff is the simplest form. It consists of an octagonal brass tube and two pairs of vertical slits. This instrument can be used for measuring angles of up to 60 degrees.

French cross-staff is a more advanced version, consisting of a hollow octagonal box atop a pole. The box has an alternate vertical sighting slit.The octagonal cross-staff helps set 45-degree angles. The instrument also features additional sighting slits at a right angle.

Another type of cross-staff is the metal arm cross-staff. This instrument is a modified version of the open cross-staff. It has four metal arms with vertical slits in the center.

This instrument can be used to sight horizons. It also features a magnetic compass at the top.

Depending on the model of cross-staff, there are several different methods of sighting. Some cross-staff feature filters can help improve accuracy. 

Total station

Total stations are designed to measure horizontal and vertical angles between points. They also calculate distances and coordinates between points. Today’s total stations are equipped with sensor technology and electronic data collectors.

To get accurate measurements, the total station needs to be level. The instrument can either be motorized or robotic.In addition to being easy to use, total stations are convenient to carry around. The instrument is lightweight, allowing for ease of movement in the field.

Total stations measure distances, angles and slopes with high accuracy. Modern total stations can also process and transfer data to computers.

Total stations from bench-mark.ca/seco/ have increased productivity in the surveying profession.