How is 3D Mapping Done?

In the dynamic world of 3D mapping, the process of capturing three-dimensional objects (real objects) can be accomplished through a diverse array of methodologies. These methodologies can be broadly classified into two overarching categories: active and passive techniques, each harnessing distinct approaches to capture the essence of our three-dimensional reality.

Active 3D Mapping:
Active methods, as the name suggests, actively engage with the environment or object being mapped by deploying a source of energy. This energy source, often in the form of laser beams or radar waves, is directed toward the subject of interest, illuminating it and facilitating the data collection process. A notable exemplar within this category is LiDAR, an acronym for Light Detection and Ranging. LiDAR operates by emitting rapid laser pulses that bounce off objects within the environment, enabling precise measurement of the distances to these objects. This laser-based approach forms the foundation of many cutting-edge 3D mapping endeavors. (Leicas BLK, FARO, DJI Dronw with L1 Sensors, etc)

Passive 3D Mapping:
In stark contrast to active methods, passive techniques chart an alternative course by forgoing the use of an external source of energy. Instead, they rely on the natural light present in the surroundings, capturing the reflections and interactions of light with the object or environment under scrutiny. Within the realm of passive 3D mapping, we encounter two notable contenders: Photogrammetry and Structure from Motion (SfM).

Photogrammetry stands as a testament to the power of imagery. This method harnesses the potential of photographs captured from various angles to construct a comprehensive 3D model. Through the artful synthesis of these images, photogrammetry unveils the depth and intricacies of objects and landscapes, weaving them into a cohesive three-dimensional tapestry. (Drone, smartphones, and 360 cameras(insta360, GoPro, Ricoh Theta Z1 ).

Structure from Motion (SfM), on the other hand, takes a dynamic approach. By leveraging the motion of a camera, SfM orchestrates the creation of 3D models that encapsulate the essence of an object or environment. As the camera moves, it captures multiple perspectives, and sophisticated algorithms meticulously stitch these perspectives together, bringing forth a vivid and detailed 3D representation.
In the realm of 3D mapping, the choice between active and passive methods is often guided by the specific requirements of a given project, the available technology, and the desired level of precision. By exploring the intricacies of these diverse techniques, we unravel the fascinating world of 3D mapping and its profound impact on our understanding of the three-dimensional realm that surrounds us.