# Modelling of Evenness of Runways as an Element of Sustainable Airport Maintenance
## 6 Conclusions  
Airport runways are subject to internal and external forces at all times and, therefore, require regular maintenance. Maintenance involves not only inspecting the runway, but also detecting irregularities that may jeopardize the safety of flight operations. In order to determine the most beneficial way of modelling runway evenness, we have included an element of research on modelling procedures in the existing research on determining the method of conducting evenness measurements and defining the runway maintenance process. In this part, we also intend to answer the question of the applicability of the newly developed method of regression plane approximation. In this paper, the use of three different groups of methods to model runway evenness is described and tested. It has been shown that certain methods are more useful than others. Each method has its advantages and disadvantages. Based on the research conducted, it can be concluded that the linear triangular irregular network interpolation provides the most useful results. The result of the analysis can be easily understood. Besides, there are many additional GIS tools to answer different spatial questions. We propose that the most appropriate runway evenness modelling method be incorporated into runway management systems at smaller airports. As it was said in the introduction, the realized measurement method is proposed for smaller airports, such as Maribor Airport. The measurement was performed in a time window of 2 h, which is feasible at smaller airports without disturbing the airport schedule. The measurement method lets one perform measurements with geodetic accuracy. The latter is also of great importance for the modelling of the evenness. The application of selected methods for modelling the evenness of the runway Edvard Rusjan Airport in Maribor showed that the considered part of the runway in the length of 300 m has an average longitudinal slope of 2% and an average transverse slope of 8%. This is in accordance with standard runway construction rules. Additional spatial analysis (isohypses with an equidistance spacing of 1 mm) showed that there are no irregularities in the considered part of the runway where water could be retained and jeopardize the safety of the airport. In the continuation of our research, we will also look into the application and comparison of other methods (such as the InSar method) to determine the irregularities of airport runways. The InSar method described in [16] is used to determine deformations at Rome airport with millimeter accuracy. In the research, we came to the realization that all the methods described in our research are suitable for modelling irregularities. Among the methods, the TIN2 method, which is time-consuming and has the most scattered results, proved to be the worst method. Among the most useful methods has been the TIN1 method, which has the advantage mainly in terms of dissemination, simplicity, and comprehensibility. All of the described methods require only a short-term closure of the airport, which does not pose an economic and logistic problem in terms of bridging the traffic. The analyzed methods are applied to the needs of runway condition analysis within the processes of sustainable runway maintenance, allowing timely intervention and thus maintaining the quality and usable condition of runways throughout their life cycle. In future research, we will try to connect our results with the results of other methods, especially the InSAR method. Conceptualization, D.S., D.D. and B.K. ; methodology, D.S. ; software, D.S. and D.D. ; validation, D.S., D.D. and B.K. ; formal analysis, B.K. ; investigation, D.S and D.D. ; resources, D.S. ; data curation, B.K. ; writing--original draft preparation, D.S. and B.K. ; writing--review and editing, D.S. and B.K. ; visualization, D.S., D.D. and B.K. ; supervision, B.K. ; project administration, D.D. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable.