Figure 1: Screenshot of a free radar siting program of Cambridge Pixel Ltd., here showing the e.g. location of the ASR 910 in Neubrandenburg-Trollenhagen (Germany).
Radar Siting means the theoretical calculations of the expected radar coverage for a given or a yet to be selected position of a radar antenna. Radar Siting is mainly the interpretation of the effects of the phenomena of the Earth’s curvature and especially line-of-sight obstructions caused by the terrain. But it includes also the effects of refraction from electromagnetic waves by the atmosphere.
In the past, this was determined by complex terrain surveying using a theodolite and measuring the angle of site (average inclination of the ground) and the angle of clearance (angle from the radar antenna to elevations on the horizon) in the direction of the target. With the possibility to access electronic map data and the use of the computing power of modern computers, the evaluation of the terrain around a possible radar image can be simulated. Simple programs, (as shown in Figure 1 and Figure 2) use only the angle of clearance. They specify the radar coverage for given flight altitudes independent of the frequency range and possible reflections on the ground and their interferences. For very high frequencies they can be accepted for a site selection without any concern.
More complicated programs also take into account the energetic maximum range of the radar (see radar range equation), a possible probability of detection, reflections on the ground and their interferences as well as possible anomalous wave propagation (e.g ducting). However, such programs are not available free of charge and require precise input of the required environment variables and parameters of the radar unit.
There are also program versions that combine the data from several radar sites and represent a common radar coverage of this radar network (see Figure 3). In contrast to free (or advertising-financed) versions, they also accept different data sources, such as, for example, instead of SRTM data from civil satellite remote sensing of the earth's surface, the more accurate digital terrain elevation data (DTED) that can be used for military purposes.
Figure 2: Radar coverage of a maritime radar located in Kiel harbor. (Screenshots made with courtesy of Cambridge Pixel Ltd.)
Figure 3: Screen shot of a paid radar siting program of Cambridge Pixel Ltd., here for a maritime radar network on the east coast of Great Britain. (Courtesy of Cambridge Pixel Ltd.)