Shadow, the user can run Longley-Rice-Hufford propagation studies using the
Irregular Terrain Model specified by the FCC Office of Engineering and
Technology (OET). This model first calculates free space loss, then terrain loss
to determine the instantaneous field intensity at any given point along a radial
path. A 180-degree sweep is performed to generate a shadow map such as the one
shown above, giving the user a snapshot of what locations receive true primary
coverage and what locations may be shadowed. This provides the best picture of
what a station's real coverage is likely to be.