The photogrammetry is traditionally known as a technique that determines metrically the shape and the position of objects from two frames.
This technique has now changed dramatically with the help of complex algorithms from computer vision, called SFM (Structure from Motion).
This NEW PHOTOGRAMMETRY is a technique that uses multiple images of the same area to rebuild the 3D geometry of the objects in an entirely automatic manner. It is used in cartography, topography, geology, engineering and architecture.
SFM – Structure From Motion
"Structure from Motion" is a calculation technique that allows to reconstruct the shape of objects through the automatic collimation of points from a set of photos. Based on computer vision algorithms, SFM extracts significant points from individual photos finding the coordinates in space of the points themselves. This first phase is called the Image Alignment: it allows the auto orientation in space and the extraction of the "key points" that will be useful in the process of elaboration of point cloud and meshes.
Dense Point Cloud
In the next step, the initial point cloud will be densified and it will be created a mesh surface called TIN ("triangulated irregular network"). Each point has got the Z coordinate and the connection between these segments form contiguous triangular faces.
By using the 3DF Zephyr Aerial photogrammetry software you can export the point cloud in popular formats or incorporate, within the software, this cloud with an external one created by a laser scanner. You can then combine these two clouds and start preparing the textured mesh.
On this surface the SFM finally manages to overlap an UV texture map, extracted from the starting picture, thus creating a real photorealistic three-dimensional model.
This is the final process of the SFM and it is also the last step of the most common photogrammetry software. With 3DF Zephyr Aerial you can also create orthophotos and extract sections from the model itself.