## 2 Materials and Methods
### Background
#### 2.2.1 Data Collection Technology
This equipment belongs to the precision Class 3 defined by the World Bank, which allows obtaining the IRI through mathematical correlations [7]. The operation of the equipment is based on the concept of using the distribution of surface deviations from an imaginary average string. It has also been defined that it is necessary to measure 200 deviations from the average string consecutively along the track and consider a constant interval between each consecutive measurement. For these conditions, it is required that the more roughness of the surface, the greater the variability of the displacements. By defining the histogram of the frequency distribution of the 200 measurements, it is possible to measure the dispersion of deviations and correlate it with the standard scale of IRI roughness. The statistical parameter that sets the dispersion's magnitude is the range of the \"D\" sample, determined after a 10% purge of the measurements [14]. The MERLIN equipment is characterized by the low cost of operation, ease of implementation, and use. However, the time it takes to perform the measurements is much longer than the time required by the laser profilometer. New technologies have now emerged for the engineering and construction industry, especially in road engineering, where the main challenge of projects is associated with the great distances they cover UAVs provide opportunities to improve productivity in inspection processes, increasingly being used in various fields, such as defense, agriculture, construction, among others. A UAV consist mainly of the aircraft, the control system, and electronic and radio equipment [15]. UAVs are useful platforms for collecting information, whether it be through sensors, cameras, or other equipment that can be added to the vehicle payload. They allow you to remotely inspect tasks that are currently carried out manually [16]. However, there are considerations to consider when using UAVs, including weather conditions, where wind and rain are determining factors, and the flight time associated with battery life [17; 18]. The use of UAVs is feasible in the construction industry, and it will be the camera alongside the GPS that is responsible for collecting the necessary spatial information. The interest in the potential for various applications such as road inspection and road-related parameters has increased in many countries [19]. The image collection process is not random and must meet certain criteria which are evidenced. Registered images should consider perpendicular orientation to the ground (Nadir) in addition to images with an oblique orientation that allows for observation of side parts of objects or surfaces that have elevation. Images will be used for viewing, identifying objects, and virtual 3D mappings [20]. This technical method has been widely used for the construction of 3D models of structures and Smart City. Additionally, the method has been applied to explore the potential use for electrical transmission lines, 3D analysis of the behavior of slopes, and 3D mappings in areas of natural disasters, obtaining good and reliable results [21]. However, 3D modeling with the use of oblique photographic techniques is rarely used in road engineering measurements. Nevertheless, this technique can assist in the planning of road design, its construction, maintenance [22]. A flight plan must be considered before starting data logging. It has to contemplate the proper translation between images [23]. The creation of 3D models requires a set of images that must be obtained, considering vertical and horizontal overlaps; the balance between vertical and horizontal overlap allows obtaining optimal results [18; 22]. It will be necessary to set flight parameters to build 3D virtual scenarios that allow for an accurate representation of reality [24; 25]. Therefore, it is important to consider some variables that condition the quality of the model obtained and influence the accuracy of the information collected.