PHOTOGRAMMETRY – REALITY CAPTURE – LASER SCANNING
Building Documenting Solutions (BDS) focuses on As-builts during the pre-construction phase. There are many different ways to capture, register and process this data. Here is a brief explanation of the most popular terminology.
We will start here. Reality Capture is the blanket term, and as you will learn below the terms laser scanning and photogrammetry are how we capture what is happening in reality. Building Surveyors like BDS use technologies such as 3D laser scanning, aerial LIDAR, and drone photogrammetry to conduct a site survey and use this data to then digitize buildings into various drafting 2D/3D software. Reality computing is used by engineers & designers with help from many applications like ReCap, Revit, AutoCAD, and Navisworks, to reduce time and increase accuracy in many types of applications.
3D scanning is the process of capturing 3D spatial information about objects in a range of the laser scanner. Most laser scanners will gather information near its spherical sightline from the scanner. It works by measuring changes in the properties of the reflected laser off an object. This can be considered in terms of the time of flight. Time of flight measures the time it takes the laser to be sent, and return from an object. It then uses the speed of light in a calculation to determine the distance. This process is better known as LIDAR ( Light Detection and Ranging)
Photogrammetry is the process of stitching together overlapping geo-tagged still images into a 3D point cloud. The algorithms register the points based on known variables from the image sensor, drone/camera position & altitude. When using a drone to capture photogrammetry, the drone flies autonomously over the job site capturing hundreds of geo-tagged images, by means of an automated flight operation. This process outputs stitched ortho-mosaic images, digital surface models, 3D point clouds, and meshes.