The basic principles of surveying have changed little over the centuries, but the instruments used by surveyors have evolved greatly. Engineering, especially civil engineering, relies heavily on quantity surveyors. There are always roads, dams, retaining walls, bridges or residential areas to be built, where surveyors are involved. They determine the limits of private property and the limits of the different political divisions. They also provide advice and data for geographic information systems (GIS), computerized databases that contain information about the characteristics and boundaries of the terrain.

Surveyors must have a thorough knowledge of physics, algebra, basic calculus, geometry and trigonometry. They must also know the laws that regulate cadastres, property and contracts. In addition, they must be able to use the delicate instruments with accuracy and precision, so that they can contribute good information for real estate and engineering records purposes applicable to structural and road construction.

Historically, distances were measured in multiple ways; such as joining the points with chains of a known length, for example, Gunter's chain") or steel tapes or invar. In order to measure horizontal distances, these chains or tapes were tensioned according to temperature, to reduce buckling and slack").

Horizontal angles were measured using a compass, which provided a magnetic declination that could be measured. This type of instrument was later improved, with inscribed discs with better angular resolution, as well as mounting telescopes with "Reticle (piece)" reticles to see more precisely above the disc. In addition, calibrated circles were added that allowed measuring vertical angles, along with vernier calipers "Caliber (instrument)") to measure fractions of a degree.

The simplest method of measuring heights is with an altimeter (basically a barometer); using air pressure as an indicator of heights. But for surveying, precision needed to be improved. For this purpose, a multitude of variants have been developed, such as exact levels. The levels are calibrated to give an exact plane of height differences between the instrument and the point in question which is measured, usually by use of a vertical measuring bar.

At the end of the 1990s, tape measures were used as basic tools in field surveying to measure the shortest distances or differences in elevation; and a theodolite fixed on a tripod to measure angles (horizontal and vertical), in combination with triangulation. Starting from a reference point, where its location and elevation are known, distances and angles of others whose location and elevation are to be known are measured. A more modern instrument is the total station, which is an electronic theodolite with a distance measuring device (EDM). Since the introduction of total stations, all optical and mechanical devices have been changed to electronic ones, with a laptop computer and software. Modern top-of-the-line stations no longer require a reflector or prism (used to return light pulses when measuring distances) to return distance measurements, they are completely automated, and can even send an email with the data to the office computer and connect to a global satellite navigation system, such as the well-known GPS. Although GPS systems have increased the speed of surveying data collection, they are still only accurate to about 20 mm. Furthermore, GPS systems do not work in areas with dense trees. This is why total stations have not completely eliminated previous instruments. Robotics allows surveyors to collect precise measurements without having to hire more workers, look through the telescope or record data. A faster way to measure (without obstacles) is to go in a helicopter with laser acoustic tracking, combined with GPS to determine the height of the helicopter. To increase accuracy, beacons" are placed on the ground (about 20 km away). This method achieves an accuracy of about 5 mm.

With the triangulation method, the first thing you have to know is the horizontal distance to the object. If it is not known or cannot be measured directly, it is calculated as explained in the triangulation article. The height of an object can then be obtained by measuring the angle between the horizontal and the line joining a point at a known distance and the top of the object. To determine the height of a mountain, sea level must be taken as a reference, but here the distances may be too great and the mountain may not be visible. So, first we must determine the position of a point, then we go to that point and make a relative measurement, and so on until the mountain top is reached.

The basic principles of surveying have changed little over the centuries, but the instruments used by surveyors have evolved greatly. Engineering, especially civil engineering, relies heavily on quantity surveyors. There are always roads, dams, retaining walls, bridges or residential areas to be built, where surveyors are involved. They determine the limits of private property and the limits of the different political divisions. They also provide advice and data for geographic information systems (GIS), computerized databases that contain information about the characteristics and boundaries of the terrain.

Surveyors must have a thorough knowledge of physics, algebra, basic calculus, geometry and trigonometry. They must also know the laws that regulate cadastres, property and contracts. In addition, they must be able to use the delicate instruments with accuracy and precision, so that they can contribute good information for real estate and engineering records purposes applicable to structural and road construction.