(RDF) accuracy are also discussed. Both turned out to be negligible for the turbine parks investigated and for Here two fundamentally different methods can be dis- the system considered, but might become important tinguished. One is using beams that are not localised in if the turbines are placed too closely to the systems. Finally, space, but that occupy the whole extent of space (and the effect of a turbine park on a Differential Global hence satisfy Maxwell's postulates). The Gaussian beams Positioning System (DGPS) system (working at 312kHz) are one possible implementation. This will be discussed in is investigated with a moment method. It turned out that the first subsection. The second uses the concept of rays, the transmitted wave towards the sea was even improved which are cuts of phenomena that do satisfy as a whole for this particular park, which was acting as parasitic Maxwell's equations (plane, cylindrical or spherical antenna at that low frequency. The three-dimensional waves). Some methods do trace the rays completely and extent of the areas, where the four different kinds of compute the different reflection and diffraction points, false echo can occur, were further quantified with which is a cumbersome geometric procedure. Some spherical-wave approximations in [LiTC05]. Paper others do launch rays, and use a receiving sphere to de- [HHBW01] uses a simple ray-optical prediction tool to termine the ones relevant to the actual receiver position. evaluate the path loss in urban areas. This information is used for UMTS load planning. One of the few papers Gaussian beams that deal with extensions of the classical UTD theory is paper [ElVa03]. Here, the theory for a lossy dielectric Paper [TaLH02] uses a Beam Launching (BL) method to wedge is derived, by taking into account both the angle of compute the fields in indoor environments. One first incidence and diffraction into the multiplication factors. decomposes the source fields into a sum of beam field by This improves significantly the diffracted fiel