The Fresnel Zone calculation can then be applied and an indication of any clearance problems gained. There are various software tools available to assist this exercise if required, but most are reliant upon the availability of topographical data to the appropriate degree of accuracy being available in digitized format. A representation of a path profile is illustrated in the image below. A path survey can be undertaken by visiting sites and observing that the path is clear of obstruction. It is important to make note of potential future interruptions to the path such as tree or foliage growth, future building plans, nearby airports and subsequent flight-path traffic, and any other transient traffic considerations.
Many operators now use specialized video products to assist in path surveys.
It is not uncommon to use both techniques for certain links. Stephen Dynes is marketing manager for Digital Microwave Corp.