# Modelling of Evenness of Runways as an Element of Sustainable Airport Maintenance
## 3 Experiment  
Conducting such an experiment at an airport is challenging due to strict regulations. In agreement with the airport operator, the field research (measurement of runway evenness and deformations) was conducted at Maribor Edvard Rusjan Airport, which is a public international airport and the second largest in Slovenia with reference code 4D. The runway is 2500 m long and 45 m wide and has a bearing capacity of PCN 86/F/A/X/T.  
The geodetic network had to be defined in such a way that it would be stable over a long period of time and would allow optimal execution and repetition of multiple measurements. The runway is an area with a simple relief structure where there are no physical obstacles; therefore, the choice of point locations for establishing the geodetic (zero) network was not challenging. The positions of the points were chosen at the edge of the survey area where stabilization of the points on the asphalt surface was possible. This ensured the permanent and physical stability of the network over a longer period of time. Seven points--20,001, 20,002, 20,003, 20,004, 20,005, 20,006, and 20,007--were permanently stabilized around the measurement area and connected to the geodetic (zero) network (Figure 1). The stabilized points of the geodetic (zero) network formed the local coordinate system, which served as the geodetic basis for determining the location of the vertical deviations. The network created from these points was used for the planar analysis and defined the study area of the existing runway of 300 m length and 45 m width [52; 53].  
Figure 1: Basic (zero) geodetic network (yellow points) and NETWORK on the runway (green points) [56].  
The various modelling procedures considered are based on one of several measurements made of the evenness of the portion of the runway under consideration. The measurement has a total of 6618 measured and calibrated points and is shown in Figure 2. For all measured points, information on the x and y geodetic coordinates and elevation at the measurement point (h = z geodetic coordinate) were included in the geodetic accuracy [51; 56].  
All models considered were created at a resolution of 2650 \(\times\) 1920, the pixel size was 0.1 \(\times\) 0.1 m, which means that the modelling was performed for a minimum runway area of 1 dm\({}^{2}\). The latter is considered to be sufficient accuracy for the needs of sustainable runway maintenance.  
In the area of the experiment determined by the geodetic base network (zero), five cross sections were defined: three longitudinal sections (P1, P2, and P3) represent the areas of expected largest runway irregularities (P1 and P3 to the left and right of the runway centerline, P2 in the middle of the runway) and two cross-sections (P4 and P5) (see Figure 3).  
All analyses were performed at the same resolution and with the application Quantum GIS (QGIS v 3.16.7-Hannover) and personal computer (processor: Intel Core i7-8700 CPU  
Figure 3: Scope of the experiment and sections considered.  
Figure 2: Measured data set.  
@ 3.20 GHz, x64, RAM: 16 GB). Selected analyses were performed using MatLab and MS Excel.  
The different runway evenness modelling methods were compared in terms of processing time required to perform the analysis (average time of 10 trials), file size (average file size after 10 trials), and content usability of each model.