In order to ensure reliable radio communication between terrestrial locations, it is important to have a reliable method of estimating the extent to which radio signals attenuate as the signals propagate between the locations, i.e., to estimate the path loss or determine a clear line of sight (LOS) path between the locations. Radio signal propagation in free space is affected by a variety of phenomena including diffraction, refraction, reflection, absorption by the atmosphere, and obstruction by material and by the earth's horizon. The radio link budget which takes into account all the gains and losses from the transmitter, through the transmission medium, to the receiver depends on a variety of factors including antenna properties (gain, directivity, front-to-back ratio, etc.), frequency or wavelength of the radio signal, interferers, natural and man-made obstructions, environmental factors such as altitude and weather, link distance, and antenna height, among other factors. Generally, the more the path between the transmitter and the receiver antennas is clear from obstructions, the less the signal losses. One way to ensure that the path is free of obstructions is to raise the height of the transmit and/or receive antennas above any obstructions that might exist along the path thereby ensuring sufficient clearance within the first Fresnel zone. To assist in designing such radio links, wireless engineers typically utilize a radio path design tool in the design process that utilizes clutter and terrain data to allow the wireless engineer to model the path loss or line of sight (LOS) between two proposed locations for radio antenna towers. However, the data model of the potential obstructions between the proposed locations is typically not precise for several reasons including the inherent finite resolution of the data model, new man-made constructions, or growth in foliage since the clutter data was collected. Furthermore, even with perfectly accurate clutter and terrain data, the precise locations proposed to erect antenna towers may turn out to be unavailable due to previously unforeseen factors such as existing un-modeled infrastructure at the site, local ordinances, construction hazards, etc. Additionally, even where the sites are available, the deployment team might prefer to relocate the antennas to minimize radio interference from newly discovered co-channel or adjacent channel radiators at the site, to collocate the antenna with others, or for any other reason. It is therefore essential to have a path design tool that readily allows for the quick selection of optimal alternative antenna placement sites around the originally proposed sites.
One of the limitations in existing radio path design tools is that the tool computations are based on pre-determined latitude and longitude coordinates for transmitting and receiving antenna towers. These tools provide little flexibility in antenna tower placement from the beginning of the design phase. The users of such path design tools have no visual display of, or ability to rapidly simulate, different antenna placements that would still meet the link budget. FIG. 1, for example, depicts an example plot 100 of currently-available design tool. The plot 100 illustrates the placement of a first antenna tower 155 at one end of a link and a second antenna tower 160 at the other end of the link. In between the towers, the plot 100 depicts intervening terrain 165, clutter 167, and the path link 170. By only considering the terrain and clutter data between the first tower 155 and second tower 160, the prior art design tool fails to provide much flexibility for wireless engineers designing radio links. For example, if the proposed site for locating the first tower 155 and/or the second tower 160 proves infeasible during site construction, wireless engineers would have to repeat the path link design in order to determine alternative antenna sites around the proposed sites that still meet the target link budget. It is therefore advantageous to have a path design tool that would provide greater flexibility to wireless engineers during the design process.