This page describes the web application Station distances. With this simple web application you can easily determine the distances between any two HiSPARC stations.
The shown distances is the great-cricle distance between the stations. Which means that it accounts for the curvature of the Earth. More information about this and the equations used to calculate the distance can be found on this page: Great-circle distance between two points.
In addition to showing the distance in meters, the time it would take light to travel this distance is also shown. This can be useful when dealing with the relativistic particles which occur in cosmic-ray induced air showers.