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SG 3 Databanks Table III-1a "Long term"

Clear-air spot measurement data (associated with Table III-1a described in Recommendation ITU-R P.311)

"Long term" data are those associated with the reference "Measured and predicted long-term distributions of tropospheric transmission loss," by A. G. Longley, R. K. Reasoner, and V. L. Fuller, Office of Telecommunications Report OT/TRER 16, 1971. These data are statistical distributions of observed signal levels as they vary over a period of time. The elementary data are usually "hourly medians" measured in decibels as attenuation relative usually to free space. Occasionally, the data are "instantaneous" values, and occasionally they are measured relative to a nominal value such as the median.

There are two files: the LTPATH file & the LTDATA file. - Download data files

The LTPATH file contains the information that is unique to the path location and its two terminals. The LTDATA file contains radio parameters and the measured quantiles. Accompanying these files is a further set called *.PFL files. They describe the terrain profiles of many of these paths.

Path names have been changed slightly from those given in the reference. Here, a path name has the form "LTxxxx" where "xxxx" is the zero-filled path number of the reference. But furthermore, many of the path names have been abandoned. The original reference considered two measurement sets to be different "paths" if they used different frequencies, different antenna heights, or different parameters of any kind. These files have used the same path name if two measurement sets used terminals at the same locations. The path name chosen was generally that of the measurement set with the smallest path number.

For LTPATH here are the column headers together with a short definition:

Path: The path name as described above
Pfl: An asterisk means that the path has a terrain profile in the accompanying *.PFL files
Xmtr: A name for the transmitter location
Xcty: Transmitter country
Xlat,Xlon: Latitude and longitude of the transmitter
Rcvr: Receiver location
Rcty: Receiver country
Rlat,Rlon: Latitude and longitude of the receiver
Dist: Path distance, kilometers
Env: Path environment--SEA for oversea
Type: Path type--LOS for line of sight

For LTDATA here are the column headers together with a short definition:

Path: Path name
Dist: Path distance, kilometers
Freq: Frequency, megahertz
Year: Year or years during which the measurements were made
Length: Length of time (usually the number of hours) involved in the measurements
Season: The time of year of the measurements--up to six of the letters WPSADN for winter, spring, summer, autumn, day, night
Xht: Transmitter antenna height, meters
Rht: Receiver antenna height, meters
Xgn: Transmitter antenna gain, dB
Rgn: Receiver antenna gain, dB
Pol: Polarization used, H=horizontal, V=vertical, C=circular
Base: Base of reference for the attenuation--relative to free space (FS), or nominal (NM) One entry reads CM, the output of a diversity combiner
A00_01,...,A99_99 The measured quantiles--the 0.01%, 0.1%, 1%, 10%, 50%, 90%, 99%, 99.9%, and 99.99% quantiles respectively