Necessity of the removal of snow in front of the ILS glide path
Monitor reflection plane
Antenna reflection plane
Dry and wet snow layers

Observations/ Measurements:

Mostly glide path angle is moving up
Rare cases have been observed with reduced glide path angle

Numerical and parametrical analysis
(Earlier publication of F.Marcum, IEEE Trans. AES, 1/98)
Introduction of a multilayer approximation -- see graph
Extension to a three dimensional treatment
Implementation into a general 3D scattering analysis tool (GTD/UTD)