Francesco Guerra

Calibration of Action Cameras for Photogrammetric Purposes

The use of action cameras for photogrammetry purposes is not widespread due to the fact that until recently the images provided by the sensors, using either still or video capture mode, were not big enough to perform and provide the appropriate analysis with the necessary photogrammetric accuracy. However, several manufacturers have recently produced and released new lightweight devices which are: (a) easy to handle, (b) capable of performing under extreme conditions and more importantly (c) able to provide both still images and video sequences of high resolution. In order to be able to use the sensor of action cameras we must apply a careful and reliable self-calibration prior to the use of any photogrammetric procedure, a relatively difficult scenario because of the short focal length of the camera and its wide angle lens that is used to obtain the maximum possible resolution of images. Special software, using functions of the OpenCV library, has been created to perform both the calibration and the production of undistorted scenes for each one of the still and video image capturing mode of a novel action camera, the GoPro Hero 3 camera that can provide still images up to 12 Mp and video up 8 Mp resolution.

The survey of cultural heritage: a long story

The conservation and enhancement of our cultural heritage (CH) require an exhaustive study in terms of position, shape, colour, geometry and also of the historical and artistic features. Survey methods have polished data acquisition techniques in line with technological progress. Today’s electronic and IT technologies, that are the tools of modern Geomatics, allow the effective survey and representation of 3D objects in different scales: from architectural structures to sculptures and also archaeological findings. All these respond perfectly to all the shades that our rich and versatile heritage present. This report does not really aim at explaining analytically the methods of Geomatics. Its main aim is to reflect on the relation between Geomatics and CH, not only highlighting their meaning but also and above all, their roots in the history of survey.

3D Technologies for the Digital Documentation of an Ancient Wooden Structure

In this paper we would like to present an operational procedure for surveys of complex structures, such as the wooden dome of SS. Giovanni e Paolo in Venice. The aim of this work was to analyse the shape and the geometry of this very articulated constructive technique: because of its complexity, a laser scanning survey, with the support of more traditional methods, such as direct and topographic survey, seemed to be the best way to analyse this structure: from the data elaboration it was possible to create a 3D model of each element as in reality, without any simplification. In line with the growing demand of digital documentation in the field of Cultural Heritage, the 3D technology applied to this research allowed an immediate reading of the whole architectural system. This paper analyses the difficulties encountered during the survey and illustrates the solutions chosen to overcome them.

Action cameras and low-cost aerial vehicles in archaeology

This research is focused on the analysis of the potential of a close range aerial photogrammetry system, which is accessible both in economic terms and in terms of simplicity of use. In particular the Go Pro Hero3 Black Edition and the Parrot Ar. Drone 2.0 were studied. There are essentially two limitations to the system and they were found for both the instruments used. Indeed, the frames captured by the Go Pro are subject to great distortion and consequently pose numerous calibration problems. On the other hand, the limitation of the system lies in the difficulty of maintaining a flight configuration suitable for photogrammetric purposes in unfavourable environmental conditions. The aim of this research is to analyse how far the limitations highlighted can influence the precision of the survey and consequent quality of the results obtained. To this end, the integrated GoPro and Parrot system was used during a survey campaign on the Altilia archaeological site, in Molise. The data obtained was compared with that gathered by more traditional methods, such as the laser scanner. The system was employed in the field of archaeology because here the question of cost often has a considerable importance and the metric aspect is frequently subordinate to the qualitative and interpretative aspects. Herein one of the products of these systems; the orthophoto will be analysed, which is particularly useful in archaeology, especially in situations such as this dig in which there aren’t many structures in elevation present. The system proposed has proven to be an accessible solution for producing an aerial documentation, which adds the excellent quality of the result to metric data for which the precision is known.

Revisiting sixteenth-century oval maps with a cartographic strain analysis

ABSTRACT A recent research on Matteo Ricci’s 1602 Chinese World Map raised, among other issues, the question of the oval graticule used before as the projection reference of the map representation. Here, we go back to the origin of the oval graticules, which almost dominated the imaging of the sixteenth-century cartography from the Contarini-Rosselli’s map in the earliest of the century to the Ortelius and Ricci maps in its latest and the beginning of seventeenth century, inspiring again many map projection makers in the twentieth century. In this paper, the revisiting and overview of the oval graticule settings of some representative sixteenth-century maps of this category are followed by studying the relevant metrical and deformational properties, carried out on a family set of these ovals (the ‘Agnese set’ of ovals), involving tools from the cartographic strain analysis. The results give some further insights on this important category of maps, typical of a period in cartography marked by the transition from the Ptolemaean standards to the post- and meta-Ptolemaean era of map representations.