Photogrammetric foundations

AXIOS 3D tracking systems are optoelectronic measuring systems based on photogrammetric methods. (i.e. close-range photogrammetry) The following will provide the foundations for an easier understanding of our tracking systems’ inner workings:

Photogrammetry

In Photogrammetry geometric properties of objects are calculated using information from image measurement in photographs. Spatial position, direction or dimensions of an object are among the information determined via photogrammetric methods.

Based on their underlying measurement methods, optical tracking systems can be separated in the following categories:

Time of Flight (TOF)

Time-of-Flight measurement (of light) allows the direct measurement of distance and direction of 3D points on a surface. Measuring quality strongly depends on tilt and surface of the measures object.

Optical Measuring Systems With Active Signalization

Such tracking systems directly project their signalisation on the measured objects. Projections can be done – for instance – via structured light (pattern projection) or laser (projection of markers).

Optical Measuring Systems With Passive Signalization

These systems use unique object characteristics (geometry, edges, …) or artificial characteristics such as target markers. AXIOS 3D tracking systems belong to this group.

Point Measuring

Boreholes and edges, but also luminous, retro-reflecting or diffusely reflecting (i.e. white) markers can be used as signalization. Single markers are detected as measuring points. If the signalization is aligned in a known geometry, these point arrays are identified and matched with the known geometry/ characteristics of a specific object.

Measuring Workflow

In a first step, images are synchronously (in case of multiple camera systems) acquired by the system’s cameras. Acquired and saved images are processed and potential measuring points are roughly identified. At this point, some blunders can already be filtered due to their size and shape.

Triangulation methods are now used to calculate the 3D-coordinates of measuring points. Calculating the spatial position of single points is possible with the multiple camera systems such as the AXIOS 3D tracking systems CamBar B1 and CamBar B2, but not with single camera systems.

If known point arrays (locators) are identified, they can used to position objects in 3D space. Objects can also be positioned in relation to each other or to a reference object.

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