# Modelling of Evenness of Runways as an Element of Sustainable Airport Maintenance
## 1 Introduction
It is unlikely that aquaplaning on runway surfaces with normal frictional properties will begin at a water depth of 3 mm or more. At first glance, it appears that airport runways are straight. Airport runways have certain, usually minor, slopes in their longitudinal and transverse profiles, but like all structures, they are subject to weathering and use that can damage the basic structure to the point where they are no longer usable (Source: [[https://aviation.stackexchange.com/questions/11857/how-flat-does-a-runway-need-to-be](https://aviation.stackexchange.com/questions/11857/how-flat-does-a-runway-need-to-be)]([https://aviation.stackexchange.com/questions/11857/how-flat-does-a-runway-need-to-be](https://aviation.stackexchange.com/questions/11857/how-flat-does-a-runway-need-to-be)), accessed on 10 March 2021). The International Civil Aviation Organization (ICAO) guidelines state that runways of a certain type (code letter-reference code) must have an appropriate slope. The reference code is determined by a combination of code elements I and II, based on the length of the runway, the wingspan of the aircraft used, and the actual outside distances of the drive wheels. main gear wheel span). The construction and condition of the airport runway shall be such that [8]:  
* has sufficient surface roughness (important for accelerating and decelerating aircraft) --otherwise, roughness must be ensured by appropriate measures (grooming),
* the horizontal slope may be: \(\bigcirc\) between 1 and 1.5% for airports with code letter C, D, E and F, and between 1 and 2% for airports with code letter A and B. In terms of elevation, individual sections of the runway may deviate from the runway centerline for runway code numbers 3 and 4 less than 1% in the first quarter, less than 0,8% in the last quarter and less than 1.25% in the remaining quarters. For runways with code numbers 2 and 4, a tolerance of less than 2% shall apply everywhere. Changes from two consecutive slopes may be less than 1.5% for code number 3 and 4 airports and less than 2% for code number 1 and 2 airports. There is also a rule concerning the transition between different slopes, namely a change of slope of less than 0.1% per 30 m for code number 4 airports, of less than 0.2% per 30 m for code number 3 airports and of less than 0.4% per 30 m for code numbers 1 and 2 airports is allowed. * the cross slope of the runway shall provide drainage of the runway. The installation of additional vegetation can help with this, as it artificially directs rainwater outside the airport runway. During operation, the runway may become soiled (e.g., from aircraft tire debris), settled (from exposure to traffic loads and soil conditions), and damaged (from traffic loads). All of the above conditions must be combined with other environmental factors, among which weather effects (along with traffic loads) have the greatest impact on runway condition. The most rapid changes and the greatest extent of runway surface changes are expected to occur where aircraft land on the runway (touchdown area) [10]. Many authors discuss the ways of determining deformations of the touch down zone in various parts. The works describe various methods and technologies of data acquisition and the acquisition of surface irregularities, among which the LiDAR and InSAR methods has recently been mentioned the most. The authors mainly describe data capture technologies, data processing accuracy, and presentation methods. Data capture methods, as described by the authors, must also be feasible during airport operation [11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25]. The established, sustainability-oriented system of runway maintenance must be based on modern methods of recording the condition of runways and take into account all criteria (technical and non-technical), on the basis of which the decision to act is technically justified.