This propagation model is fully described in Recommendation ITU-R P.1546-5. Only the land terrain profiles are implemented in SEAMCAT. The ranges of application are the same as for the ITU-R P.1546-4, except for the Tx-Rx horizontal distances that can be smaller than 1 km. In the section about Algorithm description, only the parts of Recommendation ITU-R P.1546-5 that are different from Recommendation ITU-R P.1546-4 are listed.

It must be emphasised that the measurements and modelling in this Recommendation intrinsically include the effect of terminal clutter, so it would be inappropriate to add a calculation of clutter separately.

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Figure 478: SEAMCAT Interface to the ITU-R P.1546-5 propagation model

Table 89: ITU-R Recommendation P.1546-4 propagation model

Description	Symbol	Type	Unit	Comments
Variations				Variation in basic transmission loss (it has no effect in this model, variations can be introduced using distributions in time and location percentages)
Time Percentage	p	D	%	Time variability for which the field strength value is exceeded: 1% - 50%
General environment around the Rx				Environment of the propagation around the Rx with representative values of clutter height in m: rural (10), suburban (10), urban (20), dense urban (30)
Representative clutter height around the Rx	R₂	S	m	User-specified clutter height at the Rx which overwrites any predefined value when selected
General environment around the Tx				Environment of the propagation around the Tx with representative values of clutter height in m: rural (10), suburban (10), urban (20), dense urban (30)
Representative clutter height around the Tx	R₁	S	m	User-specified clutter height at the Tx which overwrites any predefined value when selected
Location probability	q	D	%	Location variability: 1% - 99% (default value: 50%)
User specified standard deviation		S	dB	User-specified standard deviation value which overwrites any predefined value when selected
Area of location variability				500x500 m, < 2 km radius, < 50 km radius
System				Mobile, broadcasting digital and broadcasting analogue
Average profile height around the Rx		S	m	The average level of the terrain height between distances of 3 and 15 km from the Rx antenna in the direction of the Tx antenna. If Tx-Rx distance d is less than 15 km, then the terrain height is averaged between distances 0.2 d and d km.
Average profile height around the Tx		S	m	The average level of the terrain height between distances of 3 and 15 km from the Tx antenna in the direction of the Rx antenna. If Tx-Rx distance d is less than 15 km, then the terrain height is averaged between distances 0.2 d and d km.
Terrain clearance angle (at the Rx)	q_tca	S	deg	The h2 terminal's clearance angle as calculated in Section 11, noting that this is the elevation angle relative to the local horizontal
Terrain clearance angle (at the Tx)	q_eff1	S	deg	The h1 terminal’s terrain clearance angle calculated using the method in Paragraph 4.3 case a), whether or not h1 is negative
Terrain height above sea level at the Rx		S	m	Terrain height in meters above sea level at the receiver/mobile. This parameter is used in combination with the antenna height (from the Rx local environment) and the average profile height around the Rx to compute the effective antenna height.
Terrain height above sea level at the Tx		S	m	Terrain height in meters above sea level at the transmitter/base. This parameter is used in combination with the antenna height (from the Tx local environment) and the average profile height around the Tx to compute the effective antenna height.
Terminal designations				When selected the algorithm will consider the option a), b) and c) of ITU-R. 1546-5 Annex 5 §1.1. By default it is selected.

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