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Point clouds

What are they and what are they used for?

3D laser scanners scan the surfaces of the visible surroundings in a grid of individual points. The result is a point cloud made up of many millions of individual coordinates. Numerous individual scans are then registered in their correct positions to form the overall point cloud. This gives you precise 3D documentation of the scanned property.

There is a growing number of fields in which a laser scanner can be of great service. The point clouds it generates make it possible to capture highly complex structures within a short time.

A 3D point cloud model of this kind can therefore be used for monitoring urban development measures, for manufacturing spare parts in reverse engineering, and for the ongoing inspection of the condition of individual components.

You, too, should not miss out on the resulting benefits.

Laser surveying and laser-based materials testing deliver significantly better and faster results than can currently be achieved with any other measuring and testing method.

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How is a 3D point cloud created and how is it processed?

In point cloud laser scanning, a point is set for every scanned area of material. These points are integrated into a virtual model using an XYZ coordinate system. A CAD system is used for the three-dimensional display; it in turn uses the octree method to structure the points contained in a generated point cloud and to classify them in a tensor field. This process is known as segmentation. Put simply, the laser captures areas in which matter is present. CAD technology is used to process the point clouds and convert them into a CAD model.

The conversion uses a special algorithm belonging to the class of out-of-core algorithms. Only in this way can processing (i.e. the handling of the data) be guaranteed in point cloud laser scanning. Particularly when capturing entire cities or geological areas, the data volumes are often so large that even the main memory of supercomputers would not suffice. The out-of-core algorithm is responsible for distributing the relevant data across different storage media.

An algorithm is also required to display the 3D point cloud. Various options are available for CAD programs. Anyone wishing to process point clouds to create a surface model often turns to Marching Cubes, which specialises in displaying isosurfaces (enclosing surfaces). Various algorithms are available for processing point clouds; these have been brought together in the Point Library Cloud of the Open PerceptionFoundation.

What can the point cloud scanner be used for in practice?

Point cloud CAD plays a very important role in quality assurance and in checking the condition of materials as part of ongoing safety inspections. Point cloud scanners are used, for example, for the regular inspection of axles on rail vehicles. A visual inspection would not be sufficient here, as even the smallest material fractures can have catastrophic consequences, particularly on high-speed tilting trains. Another area of application for point cloud CAD generated with a laser scanner is checking the condition of bridge piers and dams.

Geographical information (known technically as spatial data) is also collected today using point cloud laser scanning. It is needed for a wide variety of purposes. A 3D point cloud can, for example, show where major rockfalls are imminent as a result of cracking following earthquakes or natural weathering. Early knowledge of such danger zones from a 3D point cloud allows timely evacuations. Spatial data is also collected in preparation for excavations and can provide indications of impending volcanic eruptions, with changes to volcanic flanks and vents being recorded with point cloud CAD at regular intervals and compared with one another.

Overall, the point cloud model has become indispensable in hazard and risk management. The geographical information is used, for example, to calculate potential flood areas in the event of storm surges and of flood waves caused by heavy rain and thaws. The surface structure derived from the 3D point cloud during processing is a useful aid in planning dykes and other flood defences. In road construction, the structure of adjacent hillsides is examined using point cloud laser scanning. This makes it possible to identify where special measures must be taken to protect against entire slopes slipping and against rockfall.

Reverse engineering also benefits from point cloud CAD

The name of this method is aptly chosen, as it involves directing laser beams of different wavelengths at the objects to be measured. The distance changes these phases. It is precisely these changes that are recorded and analysed in the phase-comparison measuring method. The respective distance is then calculated from these phase changes.

However, this particular laser scanning principle has one drawback: it can only be used to measure distances of up to 50 metres. It is therefore suitable, for example, for measuring components in reverse engineering or for surveying smaller structures.

The great advantage of the phase-comparison method is its enormous working speed. Depending on the laser scanner model, between 100,000 and 500,000 measuring points can be transferred into the point cloud. This means that even objects with very delicate structures can be measured precisely within a short time.

Conclusion: The phase-comparison method is used for laser scanning small objects. It works considerably faster than the pulse measurement method, which is used primarily for surveying parts of the earth’s surface. Both laser scanning principles guarantee a high degree of precision.

Point cloud scanners are a technology with great future potential

In future, there will be demand for all technologies that help to conserve the earth’s resources. Technologies that reduce greenhouse gas emissions are also becoming increasingly important. This alone will lead to point cloud laser scanning conquering further fields within the next few years. In addition, it enables very precise measurements and the detection of even the smallest structural defects. This helps to avoid risks arising from structural weaknesses in components. There are also the following further advantages:

  • Materials testing is possible without contact.
  • No drilling or cutting is required for depth tests.
  • Laser scanning is also suitable for large-area measurements.
  • Templates for 3D printers can be developed from the point cloud model.
  • Point cloud CAD helps with the recycling of plastics.
  • The 3D point cloud is an aid to the reconstruction of objects.
  • Point cloud scanners make it possible to replicate components that are no longer available.

If you would like to take advantage of any of these benefits, the best thing to do is to contact us right away. We will be pleased to submit an individual quotation, whether you want to inspect your structures with point cloud laser scanning or obtain geographical information.

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The point cloud can be viewed from any perspective

The rectified orthophoto of the façade of Cologne Cathedral

The point cloud in Autodesk’s ReCap software

The photo panorama view in the FARO Scene software

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