What is 3D laser Survey?
3D Laser Survey is a new generation surveying method utilizing 3D laser scanners that can capture 3D surfaces as point clouds and process it. Laser scanning-based reality capture is fundamentally changing the world of architecture and construction. Like any other technology field, for the construction industry “Time is money”. 3-Dimensional Laser Survey method enables to fast-track the reconnaissance and data gathering process required to plan and design a civil engineering project.
3D laser scanners are a device used for doing 3D surveys. This device collects 3D coordinates of a given section of an object’s surface automatically without contact of the object. The output is produced in a systematic manner in a small duration, ready for post-processing. For example, some of the latest 3D laser scanners can complete survey in less than three minutes, which would take days to complete using conventional methods. The accuracy levels of 3D survey are generally 1mm which makes it quite reliable even in structural design and building industry.
There are multiple scanning technologies used in this field and differs product to product. Usually, laser scanners emit and receive their own electromagnetic radiations. Using a 3D laser scanner, surveyors can do detailed scans of historic buildings to determine structural damage and so they can do repairs accordingly. Thus, laser scanning is completely different from former techniques. It not only to take benefit of the new opportunities it offers, but also to avoid paying for unnecessary workforce.
Applications of 3D laser Surveying in Construction?
3D laser surveying is widely adopted in the construction industry due to its obvious benefits that outrun conventional methods. One of the major applications in Three-Dimensional Laser Survey is rehabilitation and retrofitting industry in which conventional methods may not be practical. For example, historical monuments will demand contactless surveying methods to prevent damages due to human action.
3D Scanning survey is a major break through in transportation upgrade projects. It is due to its capability of gathering geometrical data of historical bridges and structures without disrupting the traffic. In these projects, tasks like widening and strengthening of existing structures are carried out. It requires reliable and accurate as-built geometrical measurements of the existing structure.
Out of my personal experience, I have adopted this technique to survey a 50-year-old rail over bridge in Melbourne. The bridge spanned over one of the most critical rail corridors in Melbourne which cannot come to halt. 3D laser survey helped to save millions in rail occupation costs and help to compare ages old as-built drawings with actual site condition. It would have been impossible to survey this inaccessible structure without the help of 3d laser survey.
Similarly, 3D survey also helps is estimation the actual condition at site and deterioration of a structure compared to as-built drawings in no time. Furthermore, these inputs are critical in estimating the of capacity of the structure and load rating.
Additionally, realtime visualization and project progress can also be carrier out using this survey methodology. The survey results will help to invoice the clients and the project managers to track the progress of work. Apart from the applications listed above, 3D Laser Survey is also used in mining industry, real-time structural deformation monitoring, accident and structural forensic investigations and quality control.
Working of a 3D Laser scanner:
Laser scanners operates in on one of the three ranging principles, they are triangulation, pulse (time of flight) or phase-comparison. Among these three principles the survey principle is triangulation method.
In this technique, a scanning head mounted on a surveyor’s tripod. Further, the scanner rotates at a high speed, while a low energy laser emits a beam with accuracy. These beam records about one million data points in a second. This data develops a point cloud and it gives an image of the structures surface.
In order to get the image of a building, the surveyor scans each side of the building and then combine in a post-processing software. Depending on the size of survey area, there will be a need of many numbers of set up positions inside and outside of the building to get a clear picture of the entire building.
3D laser survey in Historic Preservation and Restoration
It is important to preserve and protect the places and constructions that have molded our societies. 3D laser scanner permits us to capture all the details of these historic buildings i.e. unusual surfaces, architectural details, changes in construction in time, all at a level of accuracy which was difficult to surveyors formerly.
Scanners provide us with the means to capture the required data in a timely fashion. It also gives us the flexibility on how to use the data captured. Forensic studies are also introduced to understand where there are issues of structural integrity, areas of vulnerability. These are the things that might be invisible to the naked eye but are important when restoring a historic structure. 3D laser scanning also helps to figure out where to provide the HVAC systems and other fire ducts.
Three-Dimensional Laser survey Equipment
The technology evolves everyday and so does the products that uses them. The 3D laser scanning equipment used for laser surveying are classified based on several factors. These are speed of data collection, range and accuracy of readings. Further, these factors will decide the cost of the equipment.
Few major suppliers of lasers scanners are Leica, Trimble and FARO. Of course the cost varies brand to brand. One of the most advance models from Trimble costs you around 19000$ to buy one. Typically, the 3d scanners for surveying will cost anywhere between 14000$ to 61000$. The package will include Scanner, Tripod, transport case and other accessories.
Advantages of 3D Laser Surveying:
- Faster and easier than conventional methods. For example, a typical survey will take only 3 minutes.
- Collecting data with 3D surveying gives in a much more accurate project data up to 1mm accuracy
- Using 3D laser scanner and CAD software lets a project to complete in a timely manner.
- You can import Survey output data are and post-process in leading CAD and 3D software.
- Surveyors can recognize the structural damages easily.
- 3D survey in a non-dangerous method for mapping historic buildings
- This process of surveying is not reliant on the human eye so we fix it at any time when a building is untenanted, with very low levels of internal light.
- Lastly, with minimal training and technical expertise 3d survey can be easily carrier out
Limitations of 3D Laser Surveying
- Huge investment required in sophisticated scanners. Hence, 3D Laser surveying is quite expensive than manual surveying.
- Measurement of any surface beyond the scanner’s line of site is not possible. Scanners have limitations in range. However, near and far range scanners are available in market.
- 3D scanners cannot determine the material scanned.
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