Action cameras in digital Photgrammetry. Experiences of comparison of dense point clouds

Today the market offers an instrumental stock extremely widespread and commercially accessible aimed at obtaining dense point clouds for three-dimensional description in a different factor of dimensional reduction both of architectural elements and of engineering ones. The acquisition tools available have reached levels of resolution about the sensors used and so of their output, extremely high, maintaining in most general cases very small sizes. Particular groups of these cameras are the well-known action cameras, extremely compact, lightweight and performing in terms of quality thanks to the relevant resolution of the sensors used, extremely low cost and easy to use. It seems desirable that the use of such low cost equipment is aim at more qualified technical applications also performed by users although designed for use in different market. Up to now, the action camera have not found intensive use in photogrammetry, mainly because of strong distortions suffered by the frames due to the characteristics of focal linked to the optics used in the equipment and therefor to the relative problems of photos calibration. The investigation aims to check what are the limits of use of acquisitions from action cameras in light of the fact that exist always more refined calibration, recording and densification algorithms of output data. It shows a series of tests in order to evaluate and analyse the results obtained, in terms of point clouds, from action cameras through comparison with more stable results obtained with acquisitions by cameras with optical reflex.