Anchor A17.6.2 A17.6.2
,Figure 470: SEAMCAT Interface to the ITU-R Rec. P.452-14 modelAnchor F470 F470
Table 83: ITU ITU-R Recommendation P P.452-4 14 propagation modelAnchor T083 T083
Description | Symbol | Type | Unit | Comments |
Variation | - | booleanBoolean | - | Variation in path loss takes into account the uncertainty of building design, furniture, room size, etc. |
Diffraction | - | booleanBoolean | - | Select the diffraction component of the model |
Tropospheric scatter | - | booleanBoolean | - | Select the tropospheric scatter component of the model |
Ducting/layer reflection | - | booleanBoolean | - | Select the ducting/layer reflection component of the model |
Water concentration | ρ | SScalar | g/m3 | water vapour density for tropospheric study only |
Surface pressure | P | SScalar | hPa | Surface pressure (default 1013.25 hPa) |
Refraction index gradient | ΔN | SScalar | 1/km | It is the average radio-refractive index lapse-rate through the lowest 1 km of the atmosphere, provides the data upon which the appropriate effective Earth radius can be calculated. Note that ΔN is a positive quantity. |
Surface temperature | T | SScalar | Degree Celsius | Surface temperature (default 15 degree Celsius) |
Latitude | φt, φr | SScalar | Degree | Latitude of station, used in the path centre location calculation |
Additional clutter loss at the Tx | Aht | SScalar | dB | Additional clutter loss at the Tx |
Additional clutter loss at the Rx | Ahr | SScalar | dB | Additional clutter loss at the Rx |
Antenna gain at the Tx | Gt | SScalar | dB | Antenna gain of the Tx in the direction of the horizon along the great-circle interference path (dBi) |
Antenna gain at the Rx | Gr | SScalar | dB | Antenna gain of the Rx in the direction of the horizon along the great-circle interference path (dBi) |
Sea level surface refractivity | N0 | SScalar | - | The sea-level surface refractivity, is used only by the troposcatter model as a measure of location variability of the troposcatter scatter mechanism. As the scatter path calculation is based on a path geometry determined by annual or worst-month values of ΔN, there is no additional need for worst-month values of N0. The correct values of ΔN and N0 are given by the path-centre values as derived from the appropriate maps. |
Time Percentage |
| DDistribution | % | Percentage time variability from for which the field strengths value are calculated basic transmission loss is not exceeded |
The longitude parameter of the Recommendation ITU-R
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P.452-
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14 is used for the computation of the position based on a grid point data file. In SEAMCAT
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, this parameter is not used as x and y coordinates are sufficient. The latitude, however is used in SEAMCAT in evaluation of the point incidence of anomalous propagation, β0 (%), for the path centre location where β0 (%) is the time percentage for which refractive index lapse-rates exceeding 100 N units/km can be expected in the first 100 m of the lower atmosphere. β0 (%) is used to estimate the relative incidence of fully developed anomalous propagation at the latitude under consideration.