First of all, all data needed for the calculation (like length of slopes) will be provided to us by our customers, the mountain railways.
If there is only one possible way to ski down to the valley, we use the information provided by the mountain railways of these slopes. In some cases, however, there are several ways to drive into the valley. That means there are different slopes of varying lengths skiers can use. Since we can not see which way was used, we use in this case, the average of the possible slopes.