Reality Capture, a technology to collect real-world data to support BIM

Currently, the work of BIM or Building Information Modeling is very popular in the development of design and construction work processes in Thailand. In the building modeling work, there is another technology that is becoming popular and is constantly evolving in use. The so-called “Reality Capture” is a technology used for collecting data from the real world to be used as the model in the computer. It is the use of laser scanning, imaging, or the use of unmanned aerial vehicles or drones to collect information. Then, it is processed to produce accurate and fast models. The results are linked to the design process and further BIM creation. Currently, this technology is used in many ways of surveying and collecting data as follows:

1. Land survey
2. Urban planning survey
3. Surveying the area or building to be used for renovation of an area or building
4. BIM for Heritage
5. Construction quality inspection work

The Reality Capture technology has two main functions:

1. Laser Scanner
2. Photogrammetry

Laser Scanner

It has been used primarily in the survey of the original building that was built for a long time and began to be used in relation to new buildings under construction. Today, the use of a laser scanner has become an essential part of the BIM cycle and has made the overall picture and usefulness of BIM clearer and more complete. The Laser Scanner camera sends a high intensity laser beam to measure the position and surface of an object. The timer is on the travel from the origin to the object and back to the origin. The device measures the return travel time of the laser beam and calculates the distance from that object.

The capabilities of current laser scanners are capable of firing thousands of beams per second. The results obtained by using a laser scanner camera will provide the data in a form called Point Cloud, which will store the colour data of the surface that is RGB (Red, Green, Blue) with the scan in each time. With this Point Cloud file, we can convert it with Autodesk Recap Pro software for use with BIM software like Autodesk Revit or even for AutoCAD.

Laser scanner technology currently in use according to the usage method are classified into 3 types:

1. Terrestrial Laser Scanner (TLS) is a floor-standing Laser Scanner
2. Mobile Laser Scanning (MTL), also known as Mobile Mapping System, is a laser scanner in the car which can scan and store data while the car is in use
3. The Handheld Imaging Laser Scanner (HILS) is a hand-held Laser Scanner operated by holding and walking around the points to be scanned

Photogrammetry 

The principle of using multiple photographs to process geometric shapes is to take those images to calculate common points, determine their positions and create a three-dimensional image by photogrammetry technology. It can be classified into two types as follows:

Photogrammetry: Buddha images at Wat Thammaram, Ayutthaya

1. Close-range Photogrammetry is the use of photographic tools or cameras to survey ground objects by capturing every angle and surrounding objects for further processing. The number of images depends on the details of the object which usually takes pictures from 60 images up to the level of 1000 images.
2. Aerial Photogrammetry uses  an unmanned aerial vehicle (UAV) or drone to take pictures and record the coordinates of those images for further processing. The number of images that must be taken depends on the size of the survey area, desired details and the height of the survey flight.

Photogrammetry: เรือสำเภาวัดยานนาวา

Photogrammetry และแปลงเป็นไฟล์ Point Cloud: วัดปริวาสราชสงคราม

After the images have been obtained, they will be used with the software for processing into 3D images. In case of flying drones, 2D images or Ortho Photo images are usually taken for further use. Regarding the nature of the files obtained from the preparation process of Photogrammetry, they will have the Mesh that can be applied to a variety of 3D software such as 3ds Max and Maya or can be converted to a Point Cloud file to convert to building information modeling or BIM in the next step.

The software used for the main processing, as in the example above, are in 3 types:

1. Autodesk Recap Pro used for opening Point Cloud files and importing files from Laser Scan cameras or from Photogrammetry to be converted and used with BIM software such as Autodesk Revit, Navisworks
2. Autodesk Recap Photo used for processing tasks of Photogrammetry from the photos via the Autodesk cloud system.
3. Capturing Reality is a software for computing offline photogrammetry that uses our own computer to process.

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