Small Multispectral UAV Sensor and Its Image Fusion Capability in Cultural Heritage Applications

Abstract

For many decades the multispectral images of the earth’s surface and its objects were taken from multispectral sensors placed on satellites. In recent years, the technological evolution produced similar sensors (much smaller in size and weight) which can be placed on Unmanned Aerial Vehicles (UAVs), thereby allowing the collection of higher spatial resolution multispectral images. In this paper, Parrot’s small Multispectral (MS) camera Sequoia+ is used, and its images are evaluated at two archaeological sites, on the Byzantine wall (ground application) of Thessaloniki city (Greece) and on a mosaic floor (aerial application) at the archaeological site of Dion (Greece). The camera receives RGB and MS images simultaneously, a fact which does not allow image fusion to be performed, as in the standard utilization procedure of Panchromatic (PAN) and MS image of satellite passive systems. In this direction, that is, utilizing the image fusion processes of satellite PAN and MS images, this paper demonstrates that with proper digital processing the images (RGB and MS) of small MS cameras can lead to a fused image with a high spatial resolution, which retains a large percentage of the spectral information of the original MS image. The high percentage of spectral fidelity of the fused images makes it possible to perform high-precision digital measurements in archaeological sites such as the accurate digital separation of the objects, area measurements and retrieval of information not so visible with common RGB sensors via the MS and RGB data of small MS sensors.

Fusion and integration of heterogeneous close range remote sensing and geophysical data. The case of Grumentum.

“…Drone acquisitions were carried out in several flights. The acquired images were then processed within the Agisoft Metashape software in order to create orthophotomosaics in the visible wavelengths (X5S), in separate bands from blue to near infrared (Sentera AGX710), and in thermal infrared (XT2) [7][8][9][10][11][12].…”

Image Fusion Capability from Different Cameras for UAV in Cultural Heritage Applications

“…As in the previous paper [20], the same question could be asked here: when the flight height of UAVs is so small (a few meters or tens of meters), therefore a very good spatial resolution is already available in the MS image, why is it necessary to improve the spatial resolution of the MS image? First of all, an answer can be given if one considers the shift of major manufacturers of multispectral cameras for UAVs, such as MicaSense (RedEdge-P camera with a high-resolution panchromatic band), towards the creation of new cameras for UAVs which have (in addition to the MS sensor) also a PAN sensor, and have as the main argument the possibility to improve the spatial resolution of the MS image.…”

“…In a previous paper [20], RGB and MS images of the same camera for UAV, the Sequoia+ (by Parrot), were fused in order to improve the spatial resolution of the MS image and thus improve the classification accuracy by exploiting the fused image. For the same reasons, in this paper, images from different cameras for UAV will be fused.…”

Ship Graffiti in Horologion of Andronikos Kyrristos, Greece: A Comparative Study and New Evidence

“…However, the present case study of a large-scale monument with stone surfaces pioneered the application of the methods on non-conventional materials, and in the end obtained remarkable results. In the international literature, only a few cases are mentioned regarding the use of spectral imaging for studying archaeological or historical buildings and stone surfaces [41][42][43]. Furthermore, it is worth mentioning that it is the first time that these techniques have been applied systematically and comprehensively for the diagnosis of conservation status, the study of morphology and the detection of historical data on the stone surfaces of the Horologion; however, only the latter will be discussed in the present paper.…”