PathProp#

class pycraf.pathprof.PathProp(freq, temperature, pressure, lon_t, lat_t, lon_r, lat_r, h_tg, h_rg, hprof_step, timepercent, omega=<Quantity 0. %>, d_tm=None, d_lm=None, d_ct=None, d_cr=None, zone_t=CLUTTER.UNKNOWN, zone_r=CLUTTER.UNKNOWN, polarization=0, version=16, delta_N=None, N0=None, hprof_dists=None, hprof_heights=None, hprof_bearing=None, hprof_backbearing=None, generic_heights=False, base_water_density=<Quantity 7.5 g / m3>)[source]#

Bases: _PathProp

Container class that holds all path profile properties.

Parameters:

freqQuantity: Frequency of radiation [GHz]
temperatureQuantity: Ambient temperature at path midpoint [K]
pressureQuantity: Ambient pressure at path midpoint [hPa]
lon_t, lat_tQuantity: Geographic longitude/latitude of transmitter [deg]
lon_r, lat_rQuantity: Geographic longitude/latitude of receiver [deg]
h_tg, h_rgQuantity: Transmitter/receiver height over ground [m]
hprof_stepQuantity: Distance resolution of height profile along path [m]
timepercentQuantity: Time percentage [%] (maximal 50%)
omegaQuantity, optional: Fraction of the path over water [%] (see Table 3) (default: 0%)
d_tmQuantity, optional: longest continuous land (inland + coastal) section of the great-circle path [km] (default: distance between Tx and Rx)
d_lmQuantity, optional: longest continuous inland section of the great-circle path [km] (default: distance between Tx and Rx)
d_ct, d_crQuantity, optional: Distance over land from transmitter/receiver antenna to the coast along great circle interference path [km] (default: 50000 km)
zone_t, zone_rCLUTTER enum, optional: Clutter type for transmitter/receiver terminal. (default: CLUTTER.UNKNOWN)
polarizationint, optional: Polarization (default: 0) Allowed values are: 0 - horizontal, 1 - vertical
versionint, optional: ITU-R Rec. P.452 version. Allowed values are: 14, 16
delta_NQuantity, optional: Average radio-refractive index lapse-rate through the lowest 1 km of the atmosphere [N-units/km = 1/km] (default: query deltaN_N0_from_map)
N_0Quantity, optional: Sea-level surface refractivity [N-units = dimless] (default: query deltaN_N0_from_map)
hprof_distsQuantity, optional: Distance vector associated with the height profile hprof_heights. (default: query srtm_height_profile)
hprof_heightsQuantity, optional: Terrain heights profile for the distances in hprof_dists. (default: query srtm_height_profile)
hprof_bearingQuantity, optional: Start bearing of the height profile path. (default: query srtm_height_profile)
hprof_backbearingQuantity, optional: Back-bearing of the height profile path. (default: query srtm_height_profile)
generic_heightsbool: If generic_heights is set to True, heights will be set to zero. This can be useful for generic (aka flat-Earth) computations. The option is only meaningful, if the hprof_xxx parameters are set to None (which means automatic querying of the profiles). (Default: False)
base_water_densityQuantity, optional: For atmospheric attenuation, the water vapor content plays a role. In Rec. ITU-R P.452, Eq. (9a), the water content is variable (depending on the fraction of the path over the water). However, the base level is set to \(7.5~\mathrm{g}/\mathrm{m}^3\). For extraordinarily dry places, which are often used for radio astronomy, this value can be too high. (Default: 7.5 g / m^3)

Returns:

ppropPathProp instance

Notes

The diffraction-loss algorithm was changed between ITU-R P.452 version 14 and 15. The former used a Deygout method, the new one is based on a Bullington calculation with correction terms.
Set d_ct and d_cr to zero for a terminal on ship or on a sea platform; only relevant if less than 5 km.
Per default, the values for delta_N and N_0 are queried from a radiometeorological map provided with ITU-R Rec. P.452 using the function deltaN_N0_from_map. If you want to use your own values, you have to provide both, delta_N and N_0.
Per default, the height-profile data are queried from SRTM data using the srtm_height_profile function. If you want to use your own values, you have to provide all four parameters: hprof_dists, hprof_heights, bearing, and back_bearing.

If you don’t do the automatic query from SRTM data, make sure that the first element in hprof_dists is zero (transmitter location) and the last element is the distance between Tx and Rx. Also, the given lon_t, lat_t and lon_r, lat_r values should be consistent with the height profile. The bearings can be set to zero, if you don’t need to calculate boresight angles.

SRTM data tiles (*.hgt) need to be accessible by pycraf. It is assumed that these are either present in the current working directory or in the path defined by the SRTMDATA environment variable (sub-directories are also parsed). Alternatively, use the SrtmConf manager to change the directory, where pycraf looks for SRTM data, during run-time. The SrtmConf manager also offers additional features such as automatic downloading of missing tiles or applying different interpolation methods (e.g., splines). For details see Working with SRTM data.