Height is an attribute of both flight lines and photo centres.
It is the flying height above sea level.
In the majority of cases, only the flight lines have values for this attribute. However, in a small number of cases where the run was carried out at varying heights, the flying height was recorded for each photo. In these cases the average flying height to the nearest 50 metres was attributed to the flight line.
The height used in this search is the 'Height' attribute of the flight lines.