Nowadays, CAD software or digital maps allow for almost infinite enlargements, and the graphical error is still the parameter that governs measurement accuracy based on the client’s requests. This study considers scale factors smaller than 1:100 only to achieve a 1:50 scale factor, a planimetric error of less than 1 cm must be guaranteed and it is generally out of the range of drones.

For other applications, such as vast landscape, landslides or riverbeds surveying, smaller than 1:1000 graphical scales have been used. For architectural drawing, for instance, 1:50 or 1:100 graphical outputs have often been used. Remembering that the Mavic Mini 2 is an ultralight drone (it does not require a pilot’s license), it could significantly reduce costs compared to all the others.ĭepending on the type of representation that a performed topographic survey must deliver, a specific type of instrument can be adopted for the survey. Mavic Mini 2 leads to an error average of about 5 cm.

Using a regular grid of ground targets, the result obtained from Phantom 4 is one order of magnitude better than the ones obtained from the other UASs. Altimetric and planimetric residuals were reported and compared for each photogrammetric survey. For each photogrammetric flight, the boundary conditions were maintained the same, as well as the flight trajectories and the ground control point distribution. Fifty targets were installed and arranged following a kind of regular grid. The surveys’ quality was analyzed by comparing the ground targets’ coordinates measured on the field with indirect georeferencing through global navigation satellite system (GNSS). Structure-from-motion (SfM) algorithms were applied to the images taken from the UASs. Some photogrammetric reconstructions were carried out by varying flight altitude and camera settings of the 4 UAS. These unmanned aircrafts are commercial systems used mainly by private professionals. Some photogrammetric surveys were conducted in a 5 ha area using a Phantom 4 Adv, Mavic 2 Pro, Mavic Air 2 and Mavic Mini 2. This study investigates what is the more suitable UAS for specific applications considering the required scale factor, such as for architectural, environmental and restoration purposes. Comparing photogrammetric performances of four user-grade unmanned aircraft systems (UAS) is the main aim of this paper.

Metashape 1.6