Land surveyors use surveying equipment and mathematics to take measurements of the earth’s surface. The surveying task can be executed for different types of purposes and depends on the nature of the project. For instance, it can be used for determining the location of the property lines, buildings, roads, and identifying the changes in the property lines. In the construction of a building, the data and measurement of a specific environment we obtained from the surveying equipment will be used for mapping and creating the floor plans for the building. It is required to do a construction survey before starting a construction project. There are few types of surveying equipment used around the world, such as measuring tape, theodolite, total station, GPS/GNSS, 3D scanners, level, and rod. Some of the surveying tools we used today were originated since hundred years ago. With the advancement of technology, new modern types of surveying equipment and techniques are developed for faster and more precise land surveying than conventional surveying tools. We will introduce a few common types of surveying equipment and techniques in this article.
Theodolite is the predecessor of modern survey equipment that has been used for centuries. It can provide very accurate measurement by measuring the angles in the horizontal and vertical planes. It rotates along the horizontal axis and vertical axis when taking the measurements. There are two types of theodolite which are transit and non-transit. Non-transit theodolite is rarely being used nowadays. While Transit theodolite is the most commonly used type of theodolite that is able to be revolved by 180 degrees in the vertical plane. The key advantages are, it does not require extra training for the surveyor to conduct the survey and is available at a more affordable price. However, it needs at least two persons to gather the surveying data and may not be suitable for surveying over a long distance.
Transit level is the simplest type of surveying instrument which is useful and versatile. It is mainly used for surveying and building as it can measure horizontal lines and relative levels. It is very useful for creating a reference line and also provides readings of angles in precise measurements. The parts of a transit level are similar to the theodolite, it has the spirit that levels the device and a telescope that pivots horizontally to take the measurement.
Theodolite vs Transit Level
As we know that both theodolite and transit levels can be used for similar projects, but theodolite has more advantages over the transit level. Firstly, theodolite uses enclosed graduated circles and an internal magnifying optical system to take the angular readings which tends to provide a more precise measurement in angle than transit level. Secondly, it takes fewer repeat readings that can create the measurement much more quickly. Besides, the weather factors such as wind will not affect the measurement taken by the theodolite and it can be used on both flat and sloped ground.
The total station actually has the combined function of a theodolite, auto level, and electronic distance meter (EDM). EDM is using radio signals and electromagnetic waves to measure the distance between two points. It works by recording the phase changes that happen when the light travels from one point to another. These added features allow the total station to provide more accurate measurements over extreme distances and eliminate the need for another person to operate the equipment. The total station is used to take measurements of horizontal angles, vertical angles, and slope distance. Most of the total station can also remotely measure to points, so it can measure the height and structure of the building without visiting the point. In addition, it has in-built internal storage that allows the measurement to be gathered and stored electronically, which then be imported into a computer for conducting further analysis. The price of a total station is relatively high when compared with other conventional types of surveying equipment and it requires skilled personnel to operate the equipment and conduct the survey.
Drone surveying is simply a survey done from overhead by using a drone. It is normally used for surveying a large area such as roof surveys or other areas which are inaccessible or known as difficult-to-reach locations. Depending on the selection of surveying software and date sensor, it can generate a variety of measurements and data to be used for many industries. For example, a 3D photogrammetric taken by drones during the building construction stage can be used to compare with the pre-planned Building Information Modeling (BIM) objects. This allows us to identify any discrepancies between the plans and reality, helps to avoid construction errors or omissions. Without the preparation and planning required by the traditional surveying method, the drone is able to capture comparable data in a dramatically shorter time. It is fast and safe.
Global Positioning System (GPS) is able to provide positions of longitude, latitude, and height measurement precisely without using the traditional methods of measuring the distance between points. It can be used almost everywhere with the data broadcasts from the satellites. There are three different methods of GPS measurement which are Static GPS Baseline, Real-Time Kinematic (RTK) Observations, and Continuously Operating Reference Stations (CORS). These methods are most commonly used by surveyors and each of them is used for a specific application and purpose.
GPS survey equipment offers a faster speed and highest accuracy than other conventional survey techniques. However, other building structures and dense foliage may interfere and limit the function or communication of the GPS equipment. It also requires a clear view of the sky to receive the signal from the satellite.
Tips for Maintaining the Surveying Equipment
It is important to handle the survey equipment with additional care even though the manufacturer may claim that the equipment is able to handle a drop from a certain distance. We must put the surveying instrument into a safe storage box or casing when we are not using it. And we shouldn’t leave the batteries inside the unit when it is not in use for a long period of time. We are also advised to check and clean the battery terminals regularly to make sure it is free from any corrosion.
Because they are high precision equipment, we should send the equipment to be serviced at least once a year even if there aren’t any issues with the equipment. A regular service can prevent the problem from developing over time. To ensure the accuracy of positioning, checking of calibration and control points should also be done regularly or at least every two weeks.
The industry of land surveying is keep changing as new technology emerges to replace those conventional methods and equipment. The way we survey and take the measurement will only become more accurate and faster with the development of technology.
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