The right height of radiolink antenna masts in telecommunication are connected with concept of so called Fresnel Zones. Energy sent between radiolink antennas forms shape of a spindle (cigar like) with the biggest thickness in the midpoint between them. Points for antennas installation shall be found in the way that no obstacle gets into the Fresnel zone, otherwise the gain will be compromised (tree tops, houses, hill tops, or simply ground surface).
There are numerous online applets that let us calculate Fresnel zone thickness in given place between antennas. Having this information, plus maps and real terrain measurements let us find minimal mast/tower height that lets transmit all the energy between radiolink antennas.