2016).įor other applications, such as vast landscape, landslides, or riverbeds surveying, smaller than 1:1000 graphical scales have been used (Bolkas, 2019 Gracchi et al. For other applications, such as vast landscape, landslides, or riverbeds surveying, smaller graphical scales have been used (Bolkas et al. For architectural drawing, for instance, 1:50 or 1:100 graphical outputs have been often used (Bonora et al. 2017).ĭepending on the type of representation that a performed topographic survey has to deliver, a specific type of instrument can be adopted for the survey. 2018), due to the poor performances of the low-cost inertial measurement units hosted by the tested vehicles, we performed indirect georeferencing (Ekaso et al. ![]() Even if recent UAS are equipped with direct georeferencing systems (Gabrlik 2015 Pfeifer et al. Mapping with unmanned aerial vehicles (RPASs) typically involves the deployment of ground control points (GCPs) to georeference the images for generating topographic models (Hugenholtz et al. Investigating photogrammetric error and the uncertainties associated with SfM photogrammetric results are crucial tasks. Several commercial software, such as Agisoft Metashape, Meshroom, and 3DZefir, offer automated photogrammetric reconstruction routines. 2013).Īt the same time, SfM photogrammetric processing has played an increasing role in delivering digital elevation models (DEMs) from UAS-based imagery (James & Robson 2014). 2017).ĭue to the technical improvements and miniaturization of avionics and quality advancements of digital cameras, UASs have been increasingly used as remote sensing platforms (Parisi et al. Some typical applications are for architectural or archaeological purposes, regional planning, or risk analysis and mapping (Bitelli et al. Unmanned aircraft systems (UAS), commonly named drones, are gaining more and more importance in the world panorama of photogrammetric surveys (Barazzetti et al. Thanks to the increasing availability of imagery, particularly from unmanned aerial vehicles, SfM photogrammetry represents a powerful tool (James et al. It combines the utility of digital photogrammetry and ease of use derived from multi-view computer vision methods. Structure-from-motion (SfM) photogrammetry is often used as a topographic modelling technique. Remembering that the Mavic Mini 2 is an ultralight drone (does not require a pilot's license), it could significantly reduce cost compared to the other systems. With a regular grid geometry of ground targets, the Mavic Mini 2 led to an error average of about 5 cm. Average residuals from Phantom 4 Adv, about 15 mm, almost disappear compared to the other UASs the discrepancy is one order of magnitude. ![]() For each survey made by each of the four UAS, altimetric and planimetric residuals were reported and compared. The boundary conditions were maintained the same for each flight mission, flight trajectories, and the ground control point distribution on the ground. Fifty targets were installed and arranged following a reasonably regular mesh. The surveys’ quality was analyzed by comparing the ground targets’ coordinates extrapolated from the point clouds to those measured on the field with indirect georeferencing through GNSS technology. Several photogrammetric reconstructions were performed by varying essential parameters, such as flight altitude and cameras of remotely piloted aircraft systems (RPAS), applying structure-from-motion (SfM) algorithms to the images taken from the UAS. These unmanned aircrafts are commercial user–grade systems used mainly by private professionals. A series of photogrammetric surveys were conducted in a hilly area of about 5 ha using Phantom 4 Adv, Mavic 2 Pro, Mavic Air 2, and Mavic Mini 2. ![]() This study aims to investigate what is the more suitable UAS for specific applications considering the required scale factor, such as for architectural, environmental, and restoration purposes. This paper shows results of comparing performances of four unmanned aircraft systems (UAS) in terms of photogrammetric survey’s quality.
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