Surveying – A Technology Overview

Table of Contents

Surveying is used in a wide variety of areas and industries. Without surveying and the precise alignment of construction sites and buildings, no projects can be started. At the same time, surveying accompanies every phase of a construction project, which makes surveying particularly important for any project. Surveying also plays a major role with regard to the growing digitization of buildings. The following text gives you an overview of current technologies and their special fields of application.

Tachymeter (Total Station) – Surveying Target Points

The electronic total station is still one of the current surveying technologies. This is equipped with an electro-optical range finder and an angle measuring system that makes it possible to use a polar, spatial point survey. Polar means that a distance and direction can be measured simultaneously. A microprocessor calculates the horizontal distance and the height difference between the current position and the target point. Via the display, the recorded data can be saved in an internal memory. Three-dimensional coordinates can be taken from this measurement. The result consists of individual points that roughly represent the measured object. A representation by means of a detailed point cloud is too time-consuming, as each individual point would have to be measured. Therefore, only points that are important for the intended purpose are displayed. Well-known manufacturers, such as Leica, use a total station mainly in the field of industry and construction. A simple example of using a total station is the measurement of a floor plan when a new building is to be constructed. At DiConneX, we use the total station to record the control points and slam anchors, with the help of which we reference the point clouds and digital twins with millimeter precision.

Terrestrial Laser Scanners (TLS) – Stationary Distance and Direction Measurement on the Ground

Terrestrial laser scanning is a stationary 3D measurement method. With the automatic measurement technology, a laser beam is released from the scanner position in all surrounding spatial directions, which measures angles and distances. In detail, the laser source sends a laser beam onto a built-in mirror. The mirror rotates at high speed, directing the beam onto the object to be measured. The laser beam is then guided back from the object to the laser source. In this way, the measurement path can be calculated. The entire laser scanner also rotates 180° in order to be able to completely capture an area. Measurements are often taken from several points of view in order to be able to depict the building or object more precisely. The object is later reproduced in detail in a 3D point cloud due to the large number of measurement points. At the same time, a panoramic photo is taken of the object, which makes it possible to color the point cloud and create a color digitization. After surveying, the data is evaluated with the help of software and converted into a 3D model. From this, information about volume, mass and distance calculations can be read. Due to the high measuring speed, a high point density and thus a detailed,  area-wide recording is possible.

A terrestrial laser scan is used in numerous areas. Among others, in the areas of mechanical and plant engineering, architecture and land surveying. Among these, the objects to be measured can be individual components, but also complete buildings or facades. The results of such a measurement are usually sections, views, surface reliefs and BIM models. Well-known manufacturers of laser scanners are Faro, Leica Trimble or Riegl. At DiConneX, the TLS scanners are mainly used for capturing narrow areas, e.g. in the technical areas of a building or for capturing industrial facilities with millimeter precision.

Photogrammetrie – Vermessung von Objekten mithilfe von Bildern

Photogrammetry is a method used to measure objects. The measurement is not carried out directly on the object, but indirectly via images. From these images, information can be extracted that makes it possible to determine the spatial position or the three-dimensional shape of the object. As a rule, special measuring cameras are used for this purpose, which enable a non-contact reconstruction of the objects. Numerous images are taken during a recording. Based on the intersection points of these images, data of the object can be calculated. It is also possible to carry out the measurement using a mobile phone camera, but the quality of the later model will be correspondingly poorer. A measurement in the field of photogrammetry is the work of a surveyor.

Aero-photogrammetry is a sub-area of photogrammetry in which measurement images are taken from the air. An aerial survey is carried out with airplanes, helicopters or drones, among others. Surveying with drones is for us the most important procedure from photogrammetry. During this survey, the terrain is flown over in strips. In the process, images are created that are later merged into a model. Flying and measuring several times makes it possible to document and display changes to the target object, such as the progress of a building. Mobile carriers can be used to survey roads, among other things, without stopping or disturbing traffic. It is also possible to survey places that are difficult to access and later display them virtually. For example, bridges, buildings or wind turbines can be depicted in this way.

Airborne Laser Scanning (ALS)

In airborne laser scanning, technology is attached to a flying object in order to scan the surface of the object using a laser beam. This process is also called “Light Detection and Ranging”, or LiDAR for short. With this method, the terrain is also flown over in strips and with deliberate overlaps so that the entire terrain can be measured. During a measurement process, the distance between the detected point on the earth’s surface and the sensor is determined. The laser scanner generates millions of measurement points while it is still flying.

Digitale Vermessung von Gebäuden

Digital Surveying of Buildings

Drones are an important technology for us to survey buildings and construction sites. This makes it possible to survey areas that are otherwise difficult to access. Entire projects can be surveyed where a terrestrial laser scanner reaches its limits.

Mobile Mapping – Mobile 3D Data Acquisition on the Ground

Mobile Mapping – Mobile 3D data acquisition on the ground

With mobile mapping, recordings of the objects are implemented using mobile carrier platforms on the ground. Cars are usually used to measure the outside area. In addition, special rucksacks or trolleys, for example, are used indoors. A mobile mapping system is mostly used in planning and documentation, measurement and in connection with the BIM method.

An example of a mobile mapping system is the NavVis Trolley M6. With the trolley it is possible to capture interiors in 3D and thus also carry out large-scale scan projects. The survey is carried out with a 3D laser scanner and six high-resolution cameras. This makes it possible to record 360 degree images and sensor data. The head can be adjusted infinitely so that recordings in flat areas are possible. This data can be retrieved directly on the trolley tablet to see whether the surroundings have been optimally captured. A scan can be completed quickly with a quick scan process and image processing.

Another application example is the Leica Pegasus Backpack. With the help of five cameras, a fully calibrated 360° view and two LiDAR precision measuring instruments, the backpack records data from the environment. Not only is it suitable for indoor and outdoor use, it is also useful for underground surveys. The backpack synchronizes image and point cloud data, which means that comprehensive documentation of the environment can be created. The size of the backpack allows it to be checked in as luggage at the airport. This has created an advanced, mobile BIM documentation.

Hand-held Scanner

With a hand-held 3D scanner, scans of very small or hard-to-reach objects are possible. The scan can also serve as a supplement. These objects should have a size of 5 – 30 cm in order to represent them virtually. The hand scanner records the pattern with built-in cameras and then calculates the geometry of the object. An additional color camera records the color texture at the same time. Due to the low weight and mobility, which is not available with conventional scanners, many new possibilities are conceivable. In most cases, the handheld scanner must be connected to a power cable and a laptop. The results can be examined directly on the laptop and processed later in software. A hand scanner can be used for examination or documentation in the areas of architecture, the automotive industry, restoration and many more

The field of surveying is very broad. From road construction, to digitizing objects, to surveying old architecture. Different technologies are used everywhere, which in principle only do one thing – create an image. But it is precisely these procedures that are becoming increasingly important. At the same time, the possibilities to carry out a survey increase, such as with mobile mapping systems. DiConneX has specialized in the digitization of buildings and technical systems. Various technologies are used to complete a suitable result. The combination of important and constantly developing are ideal prerequisites for acting in a forward-looking manner – and that is exactly what we do!

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