From 2D photos to 3D point cloud with photogrammetry
Direct processing of 3D point clouds: Point clouds as a design basis for renovations or work on existing buildings. Accessing individual points, constructing on the existing object or measuring individual distances becomes child's play in virtual reality. Here, SEMA sets a new standard in the processing of digital 3D data and its further processing in CAD software.
The advantages of point clouds, namely the minimal errors of measurement, real measuring of all deformations of the building area calculation and distance measurements, creation of as-built plans, visualisation of objects and their virtual walk-through, can be used ideally for planning and construction. The use of point clouds in the SEMA program simplifies the work enormously and results in extremely high levels of security for inventory planning.
There are many different ways to create a 3D view of an object. The development of photogrammetry is advancing. An innovation of the ELCOVISION 10 software from company PMS AG is the fully automated generation of high-density point clouds from photos taken freely. The smallest differences in texture on the object, even with areas that are barely distinguishable by colour, are sufficient to create almost noise-free and detailed 3D point clouds. The high-precision and highly detailed 3D models have an almost laser scan quality.
Photos with different views of a staircase or building are read in the ELCOVISION 10 software during the creation of 3D point clouds from simple two-dimensional images. In this example, the Leica BLK3D was used as a camera.
The software now fully automatically calculates the viewpoints of the images when taken and, finally, calculates a 3D point cloud of the staircase. If a normal camera is used, this camera will be automatically calibrated. The BLK3D has a stereo camera and therefore the point cloud is automatically scaled correctly due to the familiar stereo base, that is the distance of the two cameras to each other. In addition, the BLK3D also has position sensors, so that the image mosaic can automatically be aligned correctly and the point cloud can be processed directly in the SEMA program. If normal cameras are used, the ELCOVISION 10 requires three points on the object to create a usable coordinate system:
Then there is also the possibility of defining the point cloud in its border limits. Thus, no unnecessary elements, which could be seen, for example, in the background of the photos, affect the further use of the point cloud. These borders are comparable to a clipping box.
Dividing the project into several point clouds: Especially when employing point clouds in staircases, the division into several point clouds, for example, storey by storey, is ideal.
The following can generally be said about the creation of a point cloud using photogrammetry: The better the quality of the photos in relation to the resolution and the views of the object – the better and more detailed the point cloud generated will be.
If a point cloud has now been created from the object, it can be exported into the SEMA point cloud for-mat (.spw) and read into the SEMA software.
Point clouds of individual storeys can be shown or hidden, or displayed visually in different ways independently of one another. The use of several 3D point clouds in a project allows for free access to planning in a virtual staircase.