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Recommendation ITU-R P.452 considers different propagation mechanisms, such as line-of-sight, diffraction, tropospheric scatter, surface ducting, elevated layer reflection and refraction and combines them into an overall prediction in which the statistics of dominance by one mechanism merge gradually into another. SEAMCAT P.452-16 implementation allows the user to choose to compute the diffraction-only portion of the propagation loss.
SEAMCAT Specific Implementation
According to Recommendation ITU-R P.452, the distance between the transmitter and the receiver is defined along the great circle path (2D) and it does not take into account the antenna height difference when computing line-of-sight propagation losses. This may lead to basic transmission loss values that are smaller than the free space loss in some rare scenarios where the path distance between transmitter and receiver is short and the difference in their antenna heights is significant. For this reason, the SEAMCAT specific implementation uses 3D distance d_{3D} between the transmitter and the receiver in the line-of-sight propagation equations of Recommendation ITU-R P.452-16 (Section 4.1) instead of the 2D distance d:
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