Ground stations

Ground stations are the receivers that carry the radio positions of light aircraft onto the Open Glider Network (OGN): OGN receivers, and FANET ground stations such as GXAirCom, which send the same beacons. Every night the monitor checks each of them by the rules of section 10.5 of the method and publishes the result as maintenance notes, the routine kind that any network of volunteer-run stations needs. Operators can look up their station and see what to adjust; regulators can see that the quality of the data is checked every day, and how.

Clubs weighing a new receiver can start from the map of where a new station would help most.

How the stations are maintained

The figures below count every station judged on the latest day. A station has an open note when one of the checks below applies to it that day. The third figure weighs each station by the radio packets it forwarded, so a station that hears three aircraft a day counts for little.

How a station is checked

A station is a name that sends receiver beacons. Each night a batch reads the previous UTC day of the recording and, for every station, measures how much of the day it was silent for more than 15 minutes, reads the figures of its status beacon (software version, clock offset, CPU temperature, radio noise) and applies the receiver checks of the data-quality method: how its signal compares with the neighbouring stations that heard the same packets (below), whether its reported position moves, whether its altitude agrees with the terrain, and whether the packets it forwards come late, declare a category other than the aircraft’s usual one or carry FLARM altitudes that disagree with other stations hearing the same fixes. A station that crosses one of the thresholds gets a maintenance note on its card, with the figure measured, what it means for the data and where the OGN documentation explains the remedy. The status beacon with its software, clock, temperature and noise figures comes from the OGN receiver software; stations running other software, such as GXAirCom, are judged by the receiver checks alone.

Two stations that receive the same FLARM packet can be compared directly. For every such packet, each reception’s signal-to-noise ratio is scaled to 10 km by adding k · log10(distance in km / 10). The figure of a station is the median of its differences with each neighbour, against the median station of the network, in dB, and a note opens when it is more than 10 dB below, a tenth of the signal power. A ridge between the station and part of the sky lowers it against the neighbours on that side only, which is why the card also says whether the station is low against nearly all its neighbours or against some.

k says how fast the signal the receivers report falls with distance, in dB for every tenfold increase of the distance. Free space gives 20. The receivers report a slower fall, 14.5 on 15 October 2026, probably because weak packets are not decoded at all and strong ones compress, so with 20 a station that hears aircraft farther away than its neighbours would look better than it is. The nightly batch therefore fits k on that day’s shared packets and publishes it with the figures.

Availability and the station’s own signal estimate are shown and open no note. A station on a mountain, run from a solar panel, may rightly sleep at night, and its own estimate averages over whatever aircraft happen to fly near it. The recording leaves out airliners, jets and devices that ask not to be tracked, so the traffic of a station is lower here than what it really carried. The full rules are section 10.5 of the method.

The rules and thresholds

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Find a station

Type the name exactly as the OGN shows it. Upper and lower case count: StChamas and STCHAMAS are two different stations. If nothing has exactly that name, the page suggests the names that differ only in case or that contain what you typed.

Station name Look up

Reading these figures