3D Laser Scanning

Useful applications of 3D laser scanning in Singapore

  1. Capture the pre and post work surface conditions of buildings and other types of civil structures in 3D digital representations for archives and baseline records.
     

  2. Road surface settlement monitoring for prioritisation of repair works
     

  3. Periodic scans to detect positional or alignment deviations of objects and features over time.
     

  4. Floor flatness assessment in high density storage and sports’ facilities to identify area of surface settlements that may cause safety hazards.

Benefits of 3D Laser Scanning in Singapore
  1. Fast data acquisition process of capturing 1,000,000 points per second.
     

  2. All the millions of points acquired through each scan are geo-referenced using GNSS, which means every single point has a 3-dimensional coordinate.
     

  3. Users may extract cross section profiles at their desk as and when needed, without having to conduct repeated site measurement works.
     

  4. Comprehensive surface area coverage and completeness of data.
     

  5. Ryobi G’s mobile 3D laser scanning requires no road closures during the data acquisition process. This reduces safety risk on roads and sites in Singapore.

Case Diary: 3D Surface Data Acquisition

1. Task

The Zurich airport had plans for remediation work on runway 14/32. For planning work, surface data collection on stock of the runway surface and the objects and marks contained therein is necessary.

The 3D laser scanning system was then deployed to conduct surface data collection process to obtain images of different objects. Due to the large number of elements to be included, the kinematic laser scanning was chosen as the suitable method. The data collection covered the area from the northern end of the runway to runway meter 2230

  1. marks

  2. panel joints, perimeter 1: All joints; Perimeter 2: TDZ joints in fire

  3. covering edges

  4. wells

  5. fire

  6. other objects within the perimeter

The evaluation is intended to reflect the following objects in a CAD file into position and height:

2. Surface data collection with kinematic laser scanning system

Figure 1: 3D Laser Scanning Equipment mounted on the vehicle

The following description explains the scanning system in general. The sequence of measurements on runway 14/32 is described in section 4.

The kinematic scanning system was installed on a test vehicle (see Figure 1). For determining the exact position of the measuring system, a combination of inertial and tachometer (INS) is used. This positioning system continuously measures the position, height and orientation of the scanning system in space, in the absolute coordinate system of the airport Zurich (Y, X, H, roll, pitch, heading). The actual recording of the environment is a high-resolution laser scanner. All visible objects are scanned in a grid of 0.5-3cm and recorded in three dimensions. In addition, the intensity of the reflected laser beam for each measuring point recorded, resulting in a created layout of different materials, such as Runway markings allowed. The result is a detailed three-dimensional point cloud before (coordinate system Baufixpunktnetz airport), which serves as a basis for further evaluations. The data are stored in an ASCII file, and thus easy for the customer to read and further processed. The absolute accuracy of this punk cloud is the positioning with total station at around 1cm.

3. Shots runway 14/32

The recordings on the runway 14/32 were carried out on the night of 9./10.01.2012.


The measured slope section was (about 250 sections) is divided into four sections, which were sequentially scanned. In each area, a tachymeter was stationed on the basis of fixed points. The scanning images were divided into five longitudinal trips distributed over the entire runway width executed. The driving speed during recording was around 6km / h. The cloud point was calculated in real time. After completion of the measurements, a three-dimensional geo-referenced point cloud of runway surface was already before. By superimposing the individual test runs was a point of min. Reached 1cm in total perimeter shooting. The entire point cloud comprises around 413 million individual points.

To control the kinematic laser scanning recordings, control points were determined independently and tachymetrically. This distinctive, highly visible points in the point cloud points are utilised as markings or corners taken from runway fires.

Figure 2: Runway on Zurich on the airport

4. Evaluation

The point clouds were imported into a 3D CAD software, which is optimised for the processing of laser scanning data.

In a first step, the position and height of the point cloud was made using the independently controlled the measured control points (see Figure 3). Through these quality checks could be shown that the absolute accuracy of the scan data is ≤ 1cm.

The elements were first evaluated in the point cloud in 2D vectorized (markings, runway fire, panel joints, etc.). Subsequently, a detailed terrain model was generated from the punk cloud to which the 2D elements were projected. Thus, a 3D CAD file, which contains all the objects inside the perimeter built. The objects were grouped in layers. The information required by the task elements could be fully evaluated. Other objects, which could not be clearly identified, were collected in a layer which was named accordingly (“unknown”).

Since the helical edge of the fire in the kinematic laser scanning images are not visible, was carried out by each lamp type (4 types), a detailed scan with a static scanner. From these recordings, a 3D model of the lamp was made, including the base plate and the screws. On the assumption that all the lamps of the same type have identical geometry, so could be fitted to the point clouds of fire from the kinematic boundary scan during the subsequent detailed evaluation, the lamp model. The fitting was carried out using the lamp head and the stand. The base plate and the coil centers have been shown in the CAD file.

Figure 3:Comparison checkpoints (yellow in white circle) with point cloud

Figure 4: Extract from CAD file

Figure 5: Extract from CAD file, detail

5. Conclusion
 

 


A complete collection of data sample of all elements distributed over an area of an approximate of 8.8ha is normally strenuous. Based on our past experiences, the conventional way of recording would mean taking on laborious works on the slopes across several time-consuming nights. 

With the use of  Kinematic Laser Scanning, all of the field work were completed within a single night. The additional benefit is that the actual recording of all of the elements were done in the office. Additionally, all of the objects and elements within the perimeter were furthermore, well evaluated, determined and vectorized with the diagnosed accuracy of ~1cm. Kinematic Laser Scanning overall has introduced and granted a safer and swifter way to collect data with accuracy. 

Now, with the three-dimensional point clouds of the runway in possession, further information such as the geographical X-Y-Z coordinates can be obtained at any moment. Supplementary benefits are also feasible, one example is the manipulation of the three-dimensional point clouds data to develop a terrain model to assist in planning probable future upgrades, maintenance or expansions. 

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