For each airport, our team manually defines a set of POIs (Points of Interest) with precise latitude, longitude, and altitude values obtained from Peak Visor (peakvisor.com).
During runtime, the application measures the altitude of these same POIs within the 3D terrain model using a sweep-hit algorithm with a 50-meter width (approximating aircraft size).
The differences between the manually entered altitudes and the model-measured altitudes are averaged across all POIs for the airport. This average represents the terrain resolution error.