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The scattering objects and effects
to be treated can be divided into several categories
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Boxtype buildings (e.g. terminals, hangars)
with predominantly flat surfaces
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Curved objects like fuel tanks, cylindrical
towers
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Irregularly shaped and structured objects
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Wire type structures (e.g. cranes, power
lines)
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Rolling, taxiing aircraft and vehicles
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Curved or spatially skewed ground (relevant
especially for the image type glideslope)
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Environmental aspects for the ground
(dry, wet, snow layers)
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Vegetation (e.g. trees, forests, corn
fields) .
The environmental effects related to
the ground and to the objects are summarized in a separate category
Due to the complexity of the electromagnetic
problem the decisive engineering tasks are the following
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adapted selection of a feasible applied
numerical method which yields an acceptable accuracy or estimate of the
system parameter in question (i.e. DDM, SDM in case of ILS)
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numerically adequate description of
the physical problem, i.e. a suitable approximation and modeling of the
ground and of the distorting objects according to accepted rules or on
a worst case basis
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sufficiently complete and correct system
modeling and analysis of the ILS (or the other system to be treated)
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expertised application of the numerical
method under continous engineering and physical control and know-how
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continous verification of the achieved
results on the basis of well founded system experience.
Essentially the solution of the actual
electromagnetic problem is a combination of Maxwells equations and system
analysis. While the system analysis is relatively straight forward, the
electromagnetic solution is a challenging task. A number of numerical methods
are known today which are in parts rigorous, some are approximations. The
most important methods are listed hereafter
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